Weeds associated with crops may impose their phytotoxic effects on
crop plants through the releas... more Weeds associated with crops may impose their phytotoxic effects on crop plants through the release of their allelochemicals and hence seriously reduce crop productivity. The present study was conducted to investigate the allelopathic effect of water soluble phenolics of weeds associated with wheat crop (Vicia sativa, Trigonella polycerata, Lathyrus aphaca, Medicago polymorpha, Melilotus indica) on germinability and biomass production of wheat seedlings by using their water extracts at 2.5% (w/v) and 5% (w/v) concentrations and residues of the same weeds with 0, 15 and 30 d decomposition periods at 2% (w/w) concentration. The results showed that the water extracts of M. indica and V. sativa at 5% concentration imposed the most inhibitory effect on energy of germination (81%) and prolonged time to 50% germination (226%), respectively; by contrast, T. polycerata and M. indica extracts at the same concentration inhibited shoot (8%) and root fresh biomass (64%). However, shoot dry biomass was exalted by the weed extracts at both concentrations with maximum increase (29%) caused by the M. indica extract at 2.5% concentration; however, root dry biomass (46%) and root/shoot ratio (51%) were decreased by M. polymorpha and M. indica extracts at 5% concentration, respectively. Residues of L. aphaca and M. polymorpha with a 30 d decomposition period proved the most toxic regarding energy of emergence (85%) and time to 50% emergence (138%), respectively; while, shoot fresh (41%) and dry biomass (26%) production were hindered mostly by M. indica and M. polymorpha residues with a 30 d decomposition period. There was the highest decrease in root fresh (64%) and dry biomass (64%), and root/shoot ratio (64%) when treatment was performed with V. sativa residues without decomposition. The results show that leachates and residues of weeds inhibit wheat germinability and biomass production through release of allelochemicals, and they are a threat to profitable crop production.
Aquatic weeds are higher plants found in the aquatic ecosystem and in anaerobic rice fields, wher... more Aquatic weeds are higher plants found in the aquatic ecosystem and in anaerobic rice fields, where they have no economic benefits. The continuance of aquatic weeds is more widespread than terrestrial weeds because in aquatic ecosystems there is very little fluctuation in the environmental conditions compared with terrestrial ecosystems. Scientists have been working to address the harmful allelopathic effects of aquatic weeds on the aquatic ecosystem, but limited information is available on the allelopathic influence of aquatic weeds on agro-ecosystems through the release of phytotoxic compounds. Phytotoxic chemicals released by different aquatic weeds into irrigation water and/or directly into rice ecosystems might have a significant inhibitory influence on germination, growth and yield field crops, soil properties and nutrients availability, population and community structure, and weed invasion. However, aquatic weeds might also be used as a potential organic alternative to chemical weed-control, due to the higher susceptibility of terrestrial weeds to the phototoxic chemicals released by aquatic weeds. Natural alternatives to chemical weed control are need of time and are crucial for a sustainable weed control. Chemical weed control is challenged, due to recent increases in herbicides resistance from weeds and to the harmful side-effects of herbicides on the environment. This review is focused on the influence of aquatic weeds on agro-ecosystems, with examples of common weeds in aquatic ecosystems and invasive aquatic weeds found in anaerobic rice. RESUMO-As plantas daninhas aquáticas são plantas superiores encontradas no ecossistema aquático e em plantações de arroz anaeróbio, onde não têm vantagens econômicas. A continuidade das plantas daninhas aquáticas é mais difundida do que a das plantas daninhas terrestres, pois nos ecossistemas aquáticos há flutuação muito baixa nas condições ambientais, em comparação com ecossistemas terrestres. Os cientistas têm trabalhado para abordar os efeitos nocivos alelopáticos dessas plantas nos ecossistemas aquáticos, mas há informações limitadas à disposição sobre a influência alelopática das plantas daninhas no ecossistema agrícola através da liberação de compostos fitotóxicos. Os compostos químicos fitotóxicos liberados por diferentes plantas daninhas aquáticas na água de irrigação e/ou diretamente no ecossistema do arroz podem ter significativa influência inibitória na germinação, no crescimento e rendimento das culturas, nas propriedades do solo e na disponibilidade de nutrientes, na estrutura da população e da comunidade e na invasão de plantas daninhas. No entanto, as plantas daninhas aquáticas podem ser usadas como uma potencial alternativa orgânica ao controle químico das
Water deficit conditions are a bearing on plant growth and development leading to diminished crop... more Water deficit conditions are a bearing on plant growth and development leading to diminished crop productivity. However, improving the crop productivity is need of the time to sustain the food security under ever increasing world population. Drought episodes are increasing with varying intensity and duration. Drought stress imposes alterations in crucial plant growth and developmental processes, including germination, plant height, stem diameter, number of leaves, leaf size and area, dry matter production and partitioning, flower and fruit production, and maturity. Nonetheless, plants show some morphological changes to cope with drought stress by lowering water loss, enhanced water uptake and maintenance of tissue water status. Some plants complete their life cycle early before the onset of drought to escape water deficit conditions. Identification of effects of drought stress on morphological attributes and morphological changes in response to drought can be promising for selection and breeding of drought resistant genotypes.
The present study was conducted to determine the effect of exogenous application of brassinolide ... more The present study was conducted to determine the effect of exogenous application of brassinolide (BR) on Leymus chinensis grown under shade, i.e., control (100% natural light), mild shade (70% natural light), and moderate shade (50% natural light). Shade substantially enhanced the plant growth, synthesis of photosynthetic pigments, photosynthetic efficiency, and chlorophyll (Chl) fluorescence attributes of L. chinensis as compared with control. The order of increase was mild shade > moderate shade > natural light except Chl content, where the order of increase was moderate shade > mild shade > natural light. Likewise, application of BR resulted in further exacerbation of plant height, plant fresh and dry mass, but less in case of Chl and carotenoids contents, gas-exchange characteristics, and Chl fluorescence attributes. The results conclude that shade significantly enhanced plant growth through alterations in physiological attributes of L. chinensis, while, application of BR may not further improve the plant growth under shade.
This study was conducted to evaluate the potential of seed priming following terminal drought on ... more This study was conducted to evaluate the potential of seed priming following terminal drought on tolerance against salt stress in bread wheat. Drought was imposed in field sown wheat at reproductive stage (BBCH growth stage 49) and was maintained till physiological maturity (BBCH growth stage 83). Seeds of bread wheat, collected from crop raised under terminal drought and/or well-watered conditions, were subjected to hydropriming and osmopriming (with 1.5% CaCl2) and were sown in soil-filled pots. After stand establishment, salt stress treatments viz. 10 mM NaCl (control) and 100 mM NaCl were imposed. Seed from terminal drought stressed source had less fat (5%), and more fibers (11%), proteins (22%) and total soluble phenolics (514%) than well-watered seed source. Salt stress reduced the plant growth, perturbed water relations and decreased yield. However, an increase in osmolytes accumulation (4-18%), malondialdehyde (MDA) (27-35%) and tissue Na contents (149-332%) was observed under salt stress. The seeds collected from drought stressed crop had better tolerance against salt stress as indicated by better yield (28%), improved water relations (3-18%), osmolytes accumulation (21-33%), and less MDA (8%) and Na contents (35%) than progeny of well-watered crop. Seed priming, osmopriming in particular, further improved the tolerance against salt stress through improvement in leaf area, water relations, leaf proline, glycine betaine and grain yield while lowering MDA and Na contents. In conclusion, changed seed composition during terminal drought and seed priming improved the salt tolerance in wheat by modulating the water relations, osmolytes accumulation and lipid peroxidation.
Modulation of growth and development under stressed conditions can be accomplished through plant ... more Modulation of growth and development under stressed conditions can be accomplished through plant growth-regulating substances. A pot study was conducted to assess morphological, physiological and biochemical changes occurring within Leymus chinensis plants in response to exogenous application of 5-aminolevulinic acid (ALA) at different concentrations (10, 50 and 100 mg L-1). Results revealed a decrease in growth, biosynthesis of photosynthetic pigments and root activity of L. chinensis plants under high temperature stress. Conversely, exogenous application of ALA proved to be an excellent remedy to ameliorate the growth and physiology of L. chinensis plants exposed to high temperature. ALA application improved plant height, leaf area, leaf length and width, plant fresh and dry weights, biosynthesis of chlorophyll a, b, total chlorophyll, carotenoids and root activity. An exacerbation was perceived in production and activity of malondialdehyde (MDA), osmolytes and enzymatic antioxidants of L. chinensis plants under high temperature. However, treatment with ALA further exalted the accumulation of proline, soluble sugars and proteins, and aggravated the activity of antioxidants viz. peroxidase, superoxide dismutase, ascorbate peroxidase, catalase and glutathione reductase while considerably lowering the production of MDA. Modulation of growth, biosynthesis of photosynthetic pigments, osmolytes and antioxidants was concentration-dependent and application of 100 mg L-1 ALA proved most advantageous. Results conclude that ALA has the potential to ameliorate growth and development of L. chinensis plants under high temperature stress through modulation of biosynthesis and activity of photosynthetic pigments, osmolytes and antioxidants and improve the high temperature stress tolerance.
A pot experiment was conducted to assess regulation of growth and physiology of Leymus chinensis ... more A pot experiment was conducted to assess regulation of growth and physiology of Leymus chinensis plants by exogenous application of 5-Aminolevulinic acid (ALA) at various concentrations (10, 50 and 100 mg/L) exposed to low temperature stress. In control distilled water was applied as spray under both normal and low temperature stress. Experiment was laid out using completely randomized design with three replications. Results revealed that low temperature stress impaired plant growth and photosynthetic pigments while elevating the accumulation of malondialdehyde (MDA), osmolytes and enzymatic antioxidants of L. chinensis plants. However, application of ALA improved the plant height, leaf area, plant fresh and dry weight, root activity, chlorophyll a, chlorophyll b and total chlorophyll content of L. chinensis plants when compared with control under low temperature stress. Treatment with ALA at a concentration of 10 and/or 50 mg/L was found better pertaining to growth while 100 mg/L was better regarding biosynthesis of photosynthetic pigments. Furthermore, ALA treatment enhanced the accumulation of soluble proteins, soluble sugars and free proline while reducing the MDA content and 10 and/or 50 mg/L ALA concentration was superior. Application of ALA also boosted the enzymatic antioxidants viz. super oxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate (APX) and glutathione reductase (GR) as compared to control at low temperature and application of 10 mg/L performed better. It may be concluded that treatment of ALA was helpful in the attainment of tolerance against low temperature stress manifested through improved growth, biosynthesis of photosynthetic pigments, higher levels of osmolytes and antioxidant enzymes, and reduced MDA content of L. chinensis plants.
Abiotic stresses are one of the major constraints to crop production and food security worldwide.... more Abiotic stresses are one of the major constraints to crop production and food security worldwide. The situation has aggravated due to the drastic and rapid changes in global climate. Heat and drought are undoubtedly the two most important stresses having huge impact on growth and productivity of the crops. It is very important to understand the physiological, biochemical, and ecological interventions related to these stresses for better management. A wide range of plant responses to these stresses could be generalized into morphological, physiological, and biochemical responses. Interestingly, this review provides a detailed account of plant responses to heat and drought stresses with special focus on highlighting the commonalities and differences. Crop growth and yields are negatively affected by sub-optimal water supply and abnormal temperatures due to physical damages, physiological disruptions, and biochemical changes. Both these stresses have multilateral impacts and therefore, complex in mechanistic action. A better understanding of plant responses to these stresses has pragmatic implication for remedies and management. A comprehensive account of conventional as well as modern approaches to deal with heat and drought stresses have also been presented here. A side-by-side critical discussion on salient responses and management strategies for these two important abiotic stresses provides a unique insight into the phenomena. A holistic approach taking into account the different management options to deal with heat and drought stress simultaneously could be a win-win approach in future.
Consequences of drought stress in crop production systems are perhaps more deleterious than other... more Consequences of drought stress in crop production systems are perhaps more deleterious than other abiotic stresses under changing climatic scenarios. Regulations of physio-biochemical responses of plants under drought stress can be used as markers for drought stress tolerance in selection and breeding. The present study was conducted to appraise the performance of three different maize hybrids (Dong Dan 80, Wan Dan 13, and Run Nong 35) under well-watered, low, moderate and SD conditions maintained at 100, 80, 60, and 40% of field capacity, respectively. Compared with well-watered conditions, drought stress caused oxidative stress by excessive production of reactive oxygen species (ROS) which led to reduced growth and yield formation in all maize hybrids; nevertheless, negative effects of drought stress were more prominent in Run Nong 35. Drought-induced osmolyte accumulation and strong enzymatic and non-enzymatic defense systems prevented the severe damage in Dong Dan 80. Overall performance of all maize hybrids under drought stress was recorded as: Dong Dan 80 > Wan Dan 13 > Run Nong 35 with 6.39, 7.35, and 16.55% yield reductions. Consequently, these biochemical traits and differential physiological responses might be helpful to develop drought tolerance genotypes that can withstand water-deficit conditions with minimum yield losses.
Water deficit is an environmental constraint restricting plant growth and productivity, and is fu... more Water deficit is an environmental constraint restricting plant growth and productivity, and is further worsened by reduced soil fertility. Plant growth-regulating substances ameliorate damaging effects of abiotic stresses, and their efficacy is improved by application of adequate nutrients. An experiment was undertaken to investigate the influence of foliar-applied nutrients (nitrogen, phosphorus, potassium: NPK) and 5-aminolevulinic acid (ALA) alone and in combination on morpho-physiological indices of the perennial grass Leymus chinensis (Trin.) Tzvel under drought and well-watered conditions. Drought stress caused a reduction in growth and photosynthetic pigments while increasing the accumulation of malondialdehyde (MDA) and osmolytes compared with well-watered conditions. However, application of NPK and ALA improved plant height, fresh and dry weights, and chlorophyll content. Production of soluble proteins and sugars, proline content, and antioxidant enzyme activities (superoxide dismutase, peroxidase, catalase, ascorbate peroxidase and glutathione reductase) were increased and MDA accumulation was lowered by application of NPK and ALA relative to the control (no application). Combined application of NPK and ALA proved more advantageous than NPK or ALA alone in exerting ameliorative effect on L. chinensis under drought-stressed conditions. The results suggest that combined application of NPK and ALA improves the growth and development of L. chinensis by modulating physiological processes and aids in sustaining drought.
The hormetic response of the most frequently used herbicide, glyphosate can be used to enhance cr... more The hormetic response of the most frequently used herbicide, glyphosate can be used to enhance crop growth and yield. A pot study was conducted twice to assess the effect of glyphosate on wheat at different doses (0, 1.8, 3.6, 7.2, 18, 36, 72, 180, 360 and 720 g a.e. ha-1) sprayed at its 3-4 leaf stage. Observations recorded three weeks after spray and maturity to determine whether growth enhancement was sustained over time. Results revealed that glyphosate application enhanced wheat growth at low doses (up to 36 g a.e. ha-1) which was sustained over time; conversely, higher doses caused phytotoxicity. Three weeks after spray, the highest plant height and shoot dry weight of wheat was observed at glyphosate dose of 18 g a.e. ha-1 when compared with the control. While, maximum number of tillers was observed at 36 and 180 g a.e. ha-1. At maturity, a similar trend was observed on plant height, shoot dry weight and number of tillers. Glyphosate at the rate of 3.6 g a.e. ha-1 produced higher number of grains; while highest spike length, 1000-grain weight and grain weight plant-1 was observed with 18 g a.e. ha-1. It was concluded that application of ultralow doses of glyphosate up to 36 g a.e. ha-1 to wheat at 3-4 leaf stage can stimulate growth.
Weeds cause losses to crops by exerting their allelopathic effect through the release of leachate... more Weeds cause losses to crops by exerting their allelopathic effect through the release of leachates and decomposition of their residues in field. The present study was conducted to assess the allelopathic effect of aqueous extracts at different concentrations [2.5% (w/v) and 5% (w/v)] and residues with different decomposition durations (0, 15 and 30 days) at 2% (w/w) concentration of five winter season leguminous weeds viz. Medicago polymorpha, Lathyrus aphaca, Melilotus indica, Trigonella polycerata and Vicia sativa against germination and seedling growth of wheat. Aqueous extracts and residues of weeds suppressed wheat germination/emergence and seedling growth in differential pattern. Compared with control, maximum reduction in germination percentage (78.4%), germination index (86.2%), root length (88.6%) and seedling vigor index (SVI) (97.4%) of wheat was shown by 5% aqueous extracts of M. indica. However, 5% aqueous extracts of L. aphaca, M. polymorpha and V. sativa produced significantly lower shoot length (9.53 cm), seedling dry weight (14.72 mg) and higher mean germination time (3.98 d), respectively. Among weed residues, T. polycerata, V. sativa and M. polymorpha showed lowest emergence percentage (35%), emergence index (0.73), SVI (398.5); root (15.72 cm) and shoot length (7.25 cm); and seedling dry weight (16.2 mg) of wheat, respectively. The differential suppressive phytotoxic ability of weeds tested seem to be due to presence of phenolic compounds namely 4-hydroxy-3-methoxy benzoic, chlorogenic, caffeic, gallic, ferulic, p-coumaric, m-coumaric, syringic and vanillic acids in different concentrations as detected by HPLC analysis of their aqueous extracts.
Intercropping of cereal and legume forages following proper planting geometry is an important str... more Intercropping of cereal and legume forages following proper planting geometry is an important strategy to achieve higher yield of quality forage. A field experiment was performed to evaluate agro-qualitative response of forage pearl millet sown as a base crop and sesbania as intercrop under different geometrical patterns (line sowing of sole pearl millet, line sowing of sole sesbania, cross planting of pearl millet and sesbania, blended seed sowing of pearl millet and sesbania, sesbania intercropping in 30 cm apart rows of pearl millet, sesbania intercropping in 45 cm apart two-row strips of pearl millet, and sesbania intercropping in 75 cm apart four-row strips of pearl millet) at Agronomic Research Area, University of Agriculture, Faisalabad. Sesbania intercropping reduced pearl millet growth. Nonetheless, least decrease in height (23%), leaf area (42%) and number of leaves (16%) of pearl millet was occurred by intercropping sesbania in 45 cm apart two-row strips of pearl millet, as compared to sole cropping of pearl millet. Total green forage yield (60%) was increased by sesbania intercropping over sole-cropping of pearl millet and the intercropping of sesbania in 45 cm apart two-row strips of pearl millet was most beneficial. Intercropping improved quality of fodder mixture, compared to sole-cropping. Crude protein (84%) was improved most by cross planting over sole pearl millet, while, crude fiber (36%) and ash contents (20%) were improved by blended seed sowing, as compared to sole cropping of sesbania. Potential benefits of forage pearl millet can be acquired by intercropping with sesbania and following the planting geometry of sesbania intercropped in 45 cm apart two-row strips of pearl millet.
Crop growth and productivity may differ under different sowing methods and planting densities. A ... more Crop growth and productivity may differ under different sowing methods and planting densities. A field experiment was conducted to evaluate the influence of different sowing methods and planting densities on growth, yield, quality and economic returns of cotton. Sowing methods included pit planting (1 m × 1 m pits), bed planting (75 cm apart beds), ridge planting (75 cm apart ridges) and line sowing with varied inter row spacing (25, 50 and 75 cm). Sowing methods significantly affected growth and yield of cotton. Pit planting imposed maximum increase in plant height (152 cm), number of monopodial branches (4.7) and sympodial branches (22.6) per plant, number of unopened (9.4) and opened bolls (41.1) per plant, and average boll weight (3.0 g) of cotton. However, highest seed-1 cotton yield (2944.5 kg ha) was obtained by flat sowing on 25 cm apart rows owing to highest planting density per unit area. Maximum ginning out turn (GOT) (41.6%) was noticed in pit planting of cotton, while, fiber quality was not affected significantly by sowing methods. Economic analysis showed that economic returns and benefit cost ratio (BCR) (1.52) was elevated by flat sowing on 25 cm apart rows. In conclusion, maximum seed cotton yield and economic returns can be acquired by flat sowing with 25 cm apart rows, while, fiber quality is independent of sowing methods.
The present study was aimed at determining the allelopathic influence
of water extracts at varyin... more The present study was aimed at determining the allelopathic influence of water extracts at varying concentrations (2.5% and 5% w/v) and residues with varying decomposition periods (0, 15 and 30 days) at 2% (w/w) concentration of four weeds (Trigonella polycerata, Vicia sativa, Lathyrus aphaca, Medicago polymorpha) against rate, synchronization and time of germination, and biomass partitioning of rice through plant and soil bioassays. Germination and biomass partitioning in rice plants were inhibited by extracts and residues. The maximum decrease in energy of germination (88.6%) and increase in time for 50% germination (210.4%) were caused by the L. aphaca extract at 5% concentration as compared to control. Root and shoot, fresh weight (13.6 and 28.6%, respectively) and dry weight (20.4 and 41.7%, respectively) were reduced by the M. polymorpha extract at 5% concentration. The Vicia sativa extract at both concentrations caused a great increase in the root/shoot ratio (125-145.8%). Trigonella polycerata and V. sativa residues decomposed for 30 days caused maximum inhibition of energy of emergence (71.4%) and their decomposition for zero and 15 days, respectively, inhibited coefficient of uniformity of emergence (78.9%). Medicago polymorpha and L. aphaca residues decomposed for 30 days exaggerated time for 50% emergence (47.1 and 50.3%, respectively) when compared with control. Medicago polymorpha residues decomposed for 30 days exerted the greatest inhibitory effect on shoot fresh weight (46.1%) and root dry weight (59.9%). Vicia sativa with 30 days and T. polycerata residues without decomposition produced the least root fresh weight (65.3%) and shoot dry weight (52.6%), respectively. The root/shoot ratio (56.8%) was increased by T. polycerata residues without decomposition. Phenolics from leguminous weeds caused inhibition of germination/emergence and biomass partitioning in rice. Therefore, these weeds must be eradicated from the field at their initial growth stages.
Water and labour scarcity pushes researchers to explore alternate sowing methods for rice like ae... more Water and labour scarcity pushes researchers to explore alternate sowing methods for rice like aerobic direct seeding but weed infestation is the major hindrance to adapt this production system. In our study, mechanical, chemical and cultural approaches were employed as weed control measures. Weed dynamics and yield parameters were recorded and economic analysis was performed. All weed control measures significantly reduced the weed density and weed dry weight as compared to control and improved harvest index. Maximum control in total weed density and total weed dry weight was achieved by hoeing followed by chemical control. The order of treatment groups in decreasing total density, total weed dry matter production and increment in harvest index was as cultural, chemical and mechanical. However, substantially highest net returns (PKR 44,049/) and highest benefit cost ratio (BCR) (1.53) were obtained by post emergence application of Penuxsulam at the rate of 15 g a.i ha-1 followed by hoeing. Inter-culture, mulching technique and Sesbania drummondi intercropping scored 1.19, 1.13 and 1.21 BCR, respectively. Thus, hoeing with hoe (25 and 45 days after sowing) and post emergence application of Penoxsulamat the rate of 15 g a.i ha-1 were most effective, profitable and economical weed control options.
Allelopathic crops can provide organic alternative to manage herbicides resistant littleseed cana... more Allelopathic crops can provide organic alternative to manage herbicides resistant littleseed canarygrass (Phalaris minor Retz.) We used mulch of four potential allelopathic crops, including sorghum, maize, sunflower and rice at 0, 6, 9 and 12 tons ha-1 to manage herbicide resistant littleseed canarygrass. Repeated pot experiment was conducted under greenhouse at the Faculty of Agriculture, University of Agriculture, Faisalabad, Pakistan, from November, 2015 to March, 2016. Results revealed that significant inhibition in emergence percentage, shoot length, root length and dry biomass of littleseed canarygrass was observed three weeks after mulch application of four allelopathic crops. This inhibition was sustained with time and caused significant reduction in plant height, dry biomass, spike length and number of seeds produced per plant at maturity. Mulches of sorghum, maize, sunflower and rice at 12 tons ha-1 caused up to 38, 25, 29 and 41% inhibition in plant height, dry biomass, spike length and number of seeds per plant respectively. Weed control efficiency of four allelopathic crop mulches was ranging 20 to 25% at mulch dose of 12 tons ha-1. However, mulches at lower doses caused growth stimulation in few growth traits. On the base of this study we conclude that these allelopathic crop mulches can be used to control herbicide resistant littleseed canarygrass due to their strong phytotoxic potential and may provide basis to develop natural herbicides to control this grass.
Salt stress is one of major problem hampering plant growth and development to a significant level... more Salt stress is one of major problem hampering plant growth and development to a significant level. In present study, 5-aminolevulinic acid (ALA) was exogenously applied to Leymus chinensis (Trin.) Tzvel. plants at various concentrations (10, 50, and 100 mg L-1) to assess its effects on morphology, physiology, and biochemistry under salt stress conditions (150 mmol NaCl L-1) as compared with control. The results indicated that salt stress substantially impaired growth, physiology and biochemistry of L. chinensis plants; nonetheless, ALA application alleviated the adverse effects of salt stress. Application of ALA improved the leaf length, leaf area, leaf conductance, plant dry biomass, water contents, and root activity of L. chinensis under stress and no stress conditions. Additionally, biosynthesis of chlorophyll, carotenoids, free proline, soluble sugars and proteins of L. chinensis plants was also increased following ALA application as compared to control, under salt stress conditions. Moreover, we also observed an enhanced activity of antioxidant defense system in L. chinensis in response to ALA application. ALA elevated the activity of enzymatic antioxidants viz. ascorbate peroxidase (APX), glutathione reductase (GR), superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) significantly scavenged reactive oxygen species thus reduced the accumulation of malondialdehyde (MDA) under salt stress as compared to control under both normal and stressed conditions. The effect of ALA on all growth and biochemical attributes was concentration dependent and application of 50 as well as 100 mg L-1 ALA proved better. The results concluded that salt stress tolerance in L. chinensis plants can be increased by exogenously applied ALA at appropriate concentration. It was suggested that L. chinensis plants were treated with ALA application of 50-100 mg L-1 was more beneficial under both normal and saline conditions. ABSTRACT
Hormetic effects of herbicides at ultra-low doses have been proved against range of crop species,... more Hormetic effects of herbicides at ultra-low doses have been proved against range of crop species, although available data of herbicides hormesis about the weeds growth is very limited. This study investigates the promotive effect of low doses of fenoxaprop-Pethyl on growth and seed production of littleseed canarygrass and wild oat. Pot experiments were conducted twice in Wire House at Agronomic Research Area, University of Agriculture, Faisalabad, during 2014-15. Seven different concentrations of fenoxaprop-P-ethyl [0, 1, 3, 6, 9, 12 and 15 g a.i. ha-1] were applied as post emergence herbicide at 3-4 leaves stage of the weeds. Results revealed that increase in growth occurred within first two weeks after spraying at fenoxaprop-P-ethyl doses 1, 3 and 6 g a.i. ha-1. More growth stimulation as compared to all other treatments was observed at fenoxaprop-P-ethyl dose 6 g a.i. ha-1. This initial increase in growth sustains with time up to the maturity of both weeds and positively influences seeds production ability. Up to 28% and 17% increase in number of seeds per plants were occurred in littleseed canarygrass and wild oat, respectively. Doses above 6 g a.i. ha-1 negatively affect the weeds growth and seed production ability.
Little is known of glyphosate-caused hormesis in weeds and how this might influence weed manageme... more Little is known of glyphosate-caused hormesis in weeds and how this might influence weed management. To test the hormetic effect of low doses of glyphosate on broad-leaved weeds, two experiments were conducted in laboratory and screenhouse. Hormetic effects of glyphosate solution in growth media (0, 65, 130, 250 and 500 g acid equivalent (a.e) ha-1) and foliar spray (0, 4, 8, 16, 32 and 64 g a.e. ha-1) were tested on four broad-leaved weeds (Coronopus didymus, Chenopodium album, Rumex dentatus and Lathyrus aphaca). Glyphosate solutions in range of 65-250 g a.e. ha-1 stimulated the germination and seedling growth of all tested weeds. However, at 500 g a.e. ha-1 germination and growth inhibition was observed. Foliar applied glyphosate at range of 4-32 g a.e. ha-1 increased the root and shoot length, dry biomass and seed production ability of all four weeds species. However, the stimulatory response was species dependent. These results indicate that glyphosate hormesis could play a significant role in altering crop/weed competition and might influence weed management.
Weeds associated with crops may impose their phytotoxic effects on
crop plants through the releas... more Weeds associated with crops may impose their phytotoxic effects on crop plants through the release of their allelochemicals and hence seriously reduce crop productivity. The present study was conducted to investigate the allelopathic effect of water soluble phenolics of weeds associated with wheat crop (Vicia sativa, Trigonella polycerata, Lathyrus aphaca, Medicago polymorpha, Melilotus indica) on germinability and biomass production of wheat seedlings by using their water extracts at 2.5% (w/v) and 5% (w/v) concentrations and residues of the same weeds with 0, 15 and 30 d decomposition periods at 2% (w/w) concentration. The results showed that the water extracts of M. indica and V. sativa at 5% concentration imposed the most inhibitory effect on energy of germination (81%) and prolonged time to 50% germination (226%), respectively; by contrast, T. polycerata and M. indica extracts at the same concentration inhibited shoot (8%) and root fresh biomass (64%). However, shoot dry biomass was exalted by the weed extracts at both concentrations with maximum increase (29%) caused by the M. indica extract at 2.5% concentration; however, root dry biomass (46%) and root/shoot ratio (51%) were decreased by M. polymorpha and M. indica extracts at 5% concentration, respectively. Residues of L. aphaca and M. polymorpha with a 30 d decomposition period proved the most toxic regarding energy of emergence (85%) and time to 50% emergence (138%), respectively; while, shoot fresh (41%) and dry biomass (26%) production were hindered mostly by M. indica and M. polymorpha residues with a 30 d decomposition period. There was the highest decrease in root fresh (64%) and dry biomass (64%), and root/shoot ratio (64%) when treatment was performed with V. sativa residues without decomposition. The results show that leachates and residues of weeds inhibit wheat germinability and biomass production through release of allelochemicals, and they are a threat to profitable crop production.
Aquatic weeds are higher plants found in the aquatic ecosystem and in anaerobic rice fields, wher... more Aquatic weeds are higher plants found in the aquatic ecosystem and in anaerobic rice fields, where they have no economic benefits. The continuance of aquatic weeds is more widespread than terrestrial weeds because in aquatic ecosystems there is very little fluctuation in the environmental conditions compared with terrestrial ecosystems. Scientists have been working to address the harmful allelopathic effects of aquatic weeds on the aquatic ecosystem, but limited information is available on the allelopathic influence of aquatic weeds on agro-ecosystems through the release of phytotoxic compounds. Phytotoxic chemicals released by different aquatic weeds into irrigation water and/or directly into rice ecosystems might have a significant inhibitory influence on germination, growth and yield field crops, soil properties and nutrients availability, population and community structure, and weed invasion. However, aquatic weeds might also be used as a potential organic alternative to chemical weed-control, due to the higher susceptibility of terrestrial weeds to the phototoxic chemicals released by aquatic weeds. Natural alternatives to chemical weed control are need of time and are crucial for a sustainable weed control. Chemical weed control is challenged, due to recent increases in herbicides resistance from weeds and to the harmful side-effects of herbicides on the environment. This review is focused on the influence of aquatic weeds on agro-ecosystems, with examples of common weeds in aquatic ecosystems and invasive aquatic weeds found in anaerobic rice. RESUMO-As plantas daninhas aquáticas são plantas superiores encontradas no ecossistema aquático e em plantações de arroz anaeróbio, onde não têm vantagens econômicas. A continuidade das plantas daninhas aquáticas é mais difundida do que a das plantas daninhas terrestres, pois nos ecossistemas aquáticos há flutuação muito baixa nas condições ambientais, em comparação com ecossistemas terrestres. Os cientistas têm trabalhado para abordar os efeitos nocivos alelopáticos dessas plantas nos ecossistemas aquáticos, mas há informações limitadas à disposição sobre a influência alelopática das plantas daninhas no ecossistema agrícola através da liberação de compostos fitotóxicos. Os compostos químicos fitotóxicos liberados por diferentes plantas daninhas aquáticas na água de irrigação e/ou diretamente no ecossistema do arroz podem ter significativa influência inibitória na germinação, no crescimento e rendimento das culturas, nas propriedades do solo e na disponibilidade de nutrientes, na estrutura da população e da comunidade e na invasão de plantas daninhas. No entanto, as plantas daninhas aquáticas podem ser usadas como uma potencial alternativa orgânica ao controle químico das
Water deficit conditions are a bearing on plant growth and development leading to diminished crop... more Water deficit conditions are a bearing on plant growth and development leading to diminished crop productivity. However, improving the crop productivity is need of the time to sustain the food security under ever increasing world population. Drought episodes are increasing with varying intensity and duration. Drought stress imposes alterations in crucial plant growth and developmental processes, including germination, plant height, stem diameter, number of leaves, leaf size and area, dry matter production and partitioning, flower and fruit production, and maturity. Nonetheless, plants show some morphological changes to cope with drought stress by lowering water loss, enhanced water uptake and maintenance of tissue water status. Some plants complete their life cycle early before the onset of drought to escape water deficit conditions. Identification of effects of drought stress on morphological attributes and morphological changes in response to drought can be promising for selection and breeding of drought resistant genotypes.
The present study was conducted to determine the effect of exogenous application of brassinolide ... more The present study was conducted to determine the effect of exogenous application of brassinolide (BR) on Leymus chinensis grown under shade, i.e., control (100% natural light), mild shade (70% natural light), and moderate shade (50% natural light). Shade substantially enhanced the plant growth, synthesis of photosynthetic pigments, photosynthetic efficiency, and chlorophyll (Chl) fluorescence attributes of L. chinensis as compared with control. The order of increase was mild shade > moderate shade > natural light except Chl content, where the order of increase was moderate shade > mild shade > natural light. Likewise, application of BR resulted in further exacerbation of plant height, plant fresh and dry mass, but less in case of Chl and carotenoids contents, gas-exchange characteristics, and Chl fluorescence attributes. The results conclude that shade significantly enhanced plant growth through alterations in physiological attributes of L. chinensis, while, application of BR may not further improve the plant growth under shade.
This study was conducted to evaluate the potential of seed priming following terminal drought on ... more This study was conducted to evaluate the potential of seed priming following terminal drought on tolerance against salt stress in bread wheat. Drought was imposed in field sown wheat at reproductive stage (BBCH growth stage 49) and was maintained till physiological maturity (BBCH growth stage 83). Seeds of bread wheat, collected from crop raised under terminal drought and/or well-watered conditions, were subjected to hydropriming and osmopriming (with 1.5% CaCl2) and were sown in soil-filled pots. After stand establishment, salt stress treatments viz. 10 mM NaCl (control) and 100 mM NaCl were imposed. Seed from terminal drought stressed source had less fat (5%), and more fibers (11%), proteins (22%) and total soluble phenolics (514%) than well-watered seed source. Salt stress reduced the plant growth, perturbed water relations and decreased yield. However, an increase in osmolytes accumulation (4-18%), malondialdehyde (MDA) (27-35%) and tissue Na contents (149-332%) was observed under salt stress. The seeds collected from drought stressed crop had better tolerance against salt stress as indicated by better yield (28%), improved water relations (3-18%), osmolytes accumulation (21-33%), and less MDA (8%) and Na contents (35%) than progeny of well-watered crop. Seed priming, osmopriming in particular, further improved the tolerance against salt stress through improvement in leaf area, water relations, leaf proline, glycine betaine and grain yield while lowering MDA and Na contents. In conclusion, changed seed composition during terminal drought and seed priming improved the salt tolerance in wheat by modulating the water relations, osmolytes accumulation and lipid peroxidation.
Modulation of growth and development under stressed conditions can be accomplished through plant ... more Modulation of growth and development under stressed conditions can be accomplished through plant growth-regulating substances. A pot study was conducted to assess morphological, physiological and biochemical changes occurring within Leymus chinensis plants in response to exogenous application of 5-aminolevulinic acid (ALA) at different concentrations (10, 50 and 100 mg L-1). Results revealed a decrease in growth, biosynthesis of photosynthetic pigments and root activity of L. chinensis plants under high temperature stress. Conversely, exogenous application of ALA proved to be an excellent remedy to ameliorate the growth and physiology of L. chinensis plants exposed to high temperature. ALA application improved plant height, leaf area, leaf length and width, plant fresh and dry weights, biosynthesis of chlorophyll a, b, total chlorophyll, carotenoids and root activity. An exacerbation was perceived in production and activity of malondialdehyde (MDA), osmolytes and enzymatic antioxidants of L. chinensis plants under high temperature. However, treatment with ALA further exalted the accumulation of proline, soluble sugars and proteins, and aggravated the activity of antioxidants viz. peroxidase, superoxide dismutase, ascorbate peroxidase, catalase and glutathione reductase while considerably lowering the production of MDA. Modulation of growth, biosynthesis of photosynthetic pigments, osmolytes and antioxidants was concentration-dependent and application of 100 mg L-1 ALA proved most advantageous. Results conclude that ALA has the potential to ameliorate growth and development of L. chinensis plants under high temperature stress through modulation of biosynthesis and activity of photosynthetic pigments, osmolytes and antioxidants and improve the high temperature stress tolerance.
A pot experiment was conducted to assess regulation of growth and physiology of Leymus chinensis ... more A pot experiment was conducted to assess regulation of growth and physiology of Leymus chinensis plants by exogenous application of 5-Aminolevulinic acid (ALA) at various concentrations (10, 50 and 100 mg/L) exposed to low temperature stress. In control distilled water was applied as spray under both normal and low temperature stress. Experiment was laid out using completely randomized design with three replications. Results revealed that low temperature stress impaired plant growth and photosynthetic pigments while elevating the accumulation of malondialdehyde (MDA), osmolytes and enzymatic antioxidants of L. chinensis plants. However, application of ALA improved the plant height, leaf area, plant fresh and dry weight, root activity, chlorophyll a, chlorophyll b and total chlorophyll content of L. chinensis plants when compared with control under low temperature stress. Treatment with ALA at a concentration of 10 and/or 50 mg/L was found better pertaining to growth while 100 mg/L was better regarding biosynthesis of photosynthetic pigments. Furthermore, ALA treatment enhanced the accumulation of soluble proteins, soluble sugars and free proline while reducing the MDA content and 10 and/or 50 mg/L ALA concentration was superior. Application of ALA also boosted the enzymatic antioxidants viz. super oxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate (APX) and glutathione reductase (GR) as compared to control at low temperature and application of 10 mg/L performed better. It may be concluded that treatment of ALA was helpful in the attainment of tolerance against low temperature stress manifested through improved growth, biosynthesis of photosynthetic pigments, higher levels of osmolytes and antioxidant enzymes, and reduced MDA content of L. chinensis plants.
Abiotic stresses are one of the major constraints to crop production and food security worldwide.... more Abiotic stresses are one of the major constraints to crop production and food security worldwide. The situation has aggravated due to the drastic and rapid changes in global climate. Heat and drought are undoubtedly the two most important stresses having huge impact on growth and productivity of the crops. It is very important to understand the physiological, biochemical, and ecological interventions related to these stresses for better management. A wide range of plant responses to these stresses could be generalized into morphological, physiological, and biochemical responses. Interestingly, this review provides a detailed account of plant responses to heat and drought stresses with special focus on highlighting the commonalities and differences. Crop growth and yields are negatively affected by sub-optimal water supply and abnormal temperatures due to physical damages, physiological disruptions, and biochemical changes. Both these stresses have multilateral impacts and therefore, complex in mechanistic action. A better understanding of plant responses to these stresses has pragmatic implication for remedies and management. A comprehensive account of conventional as well as modern approaches to deal with heat and drought stresses have also been presented here. A side-by-side critical discussion on salient responses and management strategies for these two important abiotic stresses provides a unique insight into the phenomena. A holistic approach taking into account the different management options to deal with heat and drought stress simultaneously could be a win-win approach in future.
Consequences of drought stress in crop production systems are perhaps more deleterious than other... more Consequences of drought stress in crop production systems are perhaps more deleterious than other abiotic stresses under changing climatic scenarios. Regulations of physio-biochemical responses of plants under drought stress can be used as markers for drought stress tolerance in selection and breeding. The present study was conducted to appraise the performance of three different maize hybrids (Dong Dan 80, Wan Dan 13, and Run Nong 35) under well-watered, low, moderate and SD conditions maintained at 100, 80, 60, and 40% of field capacity, respectively. Compared with well-watered conditions, drought stress caused oxidative stress by excessive production of reactive oxygen species (ROS) which led to reduced growth and yield formation in all maize hybrids; nevertheless, negative effects of drought stress were more prominent in Run Nong 35. Drought-induced osmolyte accumulation and strong enzymatic and non-enzymatic defense systems prevented the severe damage in Dong Dan 80. Overall performance of all maize hybrids under drought stress was recorded as: Dong Dan 80 > Wan Dan 13 > Run Nong 35 with 6.39, 7.35, and 16.55% yield reductions. Consequently, these biochemical traits and differential physiological responses might be helpful to develop drought tolerance genotypes that can withstand water-deficit conditions with minimum yield losses.
Water deficit is an environmental constraint restricting plant growth and productivity, and is fu... more Water deficit is an environmental constraint restricting plant growth and productivity, and is further worsened by reduced soil fertility. Plant growth-regulating substances ameliorate damaging effects of abiotic stresses, and their efficacy is improved by application of adequate nutrients. An experiment was undertaken to investigate the influence of foliar-applied nutrients (nitrogen, phosphorus, potassium: NPK) and 5-aminolevulinic acid (ALA) alone and in combination on morpho-physiological indices of the perennial grass Leymus chinensis (Trin.) Tzvel under drought and well-watered conditions. Drought stress caused a reduction in growth and photosynthetic pigments while increasing the accumulation of malondialdehyde (MDA) and osmolytes compared with well-watered conditions. However, application of NPK and ALA improved plant height, fresh and dry weights, and chlorophyll content. Production of soluble proteins and sugars, proline content, and antioxidant enzyme activities (superoxide dismutase, peroxidase, catalase, ascorbate peroxidase and glutathione reductase) were increased and MDA accumulation was lowered by application of NPK and ALA relative to the control (no application). Combined application of NPK and ALA proved more advantageous than NPK or ALA alone in exerting ameliorative effect on L. chinensis under drought-stressed conditions. The results suggest that combined application of NPK and ALA improves the growth and development of L. chinensis by modulating physiological processes and aids in sustaining drought.
The hormetic response of the most frequently used herbicide, glyphosate can be used to enhance cr... more The hormetic response of the most frequently used herbicide, glyphosate can be used to enhance crop growth and yield. A pot study was conducted twice to assess the effect of glyphosate on wheat at different doses (0, 1.8, 3.6, 7.2, 18, 36, 72, 180, 360 and 720 g a.e. ha-1) sprayed at its 3-4 leaf stage. Observations recorded three weeks after spray and maturity to determine whether growth enhancement was sustained over time. Results revealed that glyphosate application enhanced wheat growth at low doses (up to 36 g a.e. ha-1) which was sustained over time; conversely, higher doses caused phytotoxicity. Three weeks after spray, the highest plant height and shoot dry weight of wheat was observed at glyphosate dose of 18 g a.e. ha-1 when compared with the control. While, maximum number of tillers was observed at 36 and 180 g a.e. ha-1. At maturity, a similar trend was observed on plant height, shoot dry weight and number of tillers. Glyphosate at the rate of 3.6 g a.e. ha-1 produced higher number of grains; while highest spike length, 1000-grain weight and grain weight plant-1 was observed with 18 g a.e. ha-1. It was concluded that application of ultralow doses of glyphosate up to 36 g a.e. ha-1 to wheat at 3-4 leaf stage can stimulate growth.
Weeds cause losses to crops by exerting their allelopathic effect through the release of leachate... more Weeds cause losses to crops by exerting their allelopathic effect through the release of leachates and decomposition of their residues in field. The present study was conducted to assess the allelopathic effect of aqueous extracts at different concentrations [2.5% (w/v) and 5% (w/v)] and residues with different decomposition durations (0, 15 and 30 days) at 2% (w/w) concentration of five winter season leguminous weeds viz. Medicago polymorpha, Lathyrus aphaca, Melilotus indica, Trigonella polycerata and Vicia sativa against germination and seedling growth of wheat. Aqueous extracts and residues of weeds suppressed wheat germination/emergence and seedling growth in differential pattern. Compared with control, maximum reduction in germination percentage (78.4%), germination index (86.2%), root length (88.6%) and seedling vigor index (SVI) (97.4%) of wheat was shown by 5% aqueous extracts of M. indica. However, 5% aqueous extracts of L. aphaca, M. polymorpha and V. sativa produced significantly lower shoot length (9.53 cm), seedling dry weight (14.72 mg) and higher mean germination time (3.98 d), respectively. Among weed residues, T. polycerata, V. sativa and M. polymorpha showed lowest emergence percentage (35%), emergence index (0.73), SVI (398.5); root (15.72 cm) and shoot length (7.25 cm); and seedling dry weight (16.2 mg) of wheat, respectively. The differential suppressive phytotoxic ability of weeds tested seem to be due to presence of phenolic compounds namely 4-hydroxy-3-methoxy benzoic, chlorogenic, caffeic, gallic, ferulic, p-coumaric, m-coumaric, syringic and vanillic acids in different concentrations as detected by HPLC analysis of their aqueous extracts.
Intercropping of cereal and legume forages following proper planting geometry is an important str... more Intercropping of cereal and legume forages following proper planting geometry is an important strategy to achieve higher yield of quality forage. A field experiment was performed to evaluate agro-qualitative response of forage pearl millet sown as a base crop and sesbania as intercrop under different geometrical patterns (line sowing of sole pearl millet, line sowing of sole sesbania, cross planting of pearl millet and sesbania, blended seed sowing of pearl millet and sesbania, sesbania intercropping in 30 cm apart rows of pearl millet, sesbania intercropping in 45 cm apart two-row strips of pearl millet, and sesbania intercropping in 75 cm apart four-row strips of pearl millet) at Agronomic Research Area, University of Agriculture, Faisalabad. Sesbania intercropping reduced pearl millet growth. Nonetheless, least decrease in height (23%), leaf area (42%) and number of leaves (16%) of pearl millet was occurred by intercropping sesbania in 45 cm apart two-row strips of pearl millet, as compared to sole cropping of pearl millet. Total green forage yield (60%) was increased by sesbania intercropping over sole-cropping of pearl millet and the intercropping of sesbania in 45 cm apart two-row strips of pearl millet was most beneficial. Intercropping improved quality of fodder mixture, compared to sole-cropping. Crude protein (84%) was improved most by cross planting over sole pearl millet, while, crude fiber (36%) and ash contents (20%) were improved by blended seed sowing, as compared to sole cropping of sesbania. Potential benefits of forage pearl millet can be acquired by intercropping with sesbania and following the planting geometry of sesbania intercropped in 45 cm apart two-row strips of pearl millet.
Crop growth and productivity may differ under different sowing methods and planting densities. A ... more Crop growth and productivity may differ under different sowing methods and planting densities. A field experiment was conducted to evaluate the influence of different sowing methods and planting densities on growth, yield, quality and economic returns of cotton. Sowing methods included pit planting (1 m × 1 m pits), bed planting (75 cm apart beds), ridge planting (75 cm apart ridges) and line sowing with varied inter row spacing (25, 50 and 75 cm). Sowing methods significantly affected growth and yield of cotton. Pit planting imposed maximum increase in plant height (152 cm), number of monopodial branches (4.7) and sympodial branches (22.6) per plant, number of unopened (9.4) and opened bolls (41.1) per plant, and average boll weight (3.0 g) of cotton. However, highest seed-1 cotton yield (2944.5 kg ha) was obtained by flat sowing on 25 cm apart rows owing to highest planting density per unit area. Maximum ginning out turn (GOT) (41.6%) was noticed in pit planting of cotton, while, fiber quality was not affected significantly by sowing methods. Economic analysis showed that economic returns and benefit cost ratio (BCR) (1.52) was elevated by flat sowing on 25 cm apart rows. In conclusion, maximum seed cotton yield and economic returns can be acquired by flat sowing with 25 cm apart rows, while, fiber quality is independent of sowing methods.
The present study was aimed at determining the allelopathic influence
of water extracts at varyin... more The present study was aimed at determining the allelopathic influence of water extracts at varying concentrations (2.5% and 5% w/v) and residues with varying decomposition periods (0, 15 and 30 days) at 2% (w/w) concentration of four weeds (Trigonella polycerata, Vicia sativa, Lathyrus aphaca, Medicago polymorpha) against rate, synchronization and time of germination, and biomass partitioning of rice through plant and soil bioassays. Germination and biomass partitioning in rice plants were inhibited by extracts and residues. The maximum decrease in energy of germination (88.6%) and increase in time for 50% germination (210.4%) were caused by the L. aphaca extract at 5% concentration as compared to control. Root and shoot, fresh weight (13.6 and 28.6%, respectively) and dry weight (20.4 and 41.7%, respectively) were reduced by the M. polymorpha extract at 5% concentration. The Vicia sativa extract at both concentrations caused a great increase in the root/shoot ratio (125-145.8%). Trigonella polycerata and V. sativa residues decomposed for 30 days caused maximum inhibition of energy of emergence (71.4%) and their decomposition for zero and 15 days, respectively, inhibited coefficient of uniformity of emergence (78.9%). Medicago polymorpha and L. aphaca residues decomposed for 30 days exaggerated time for 50% emergence (47.1 and 50.3%, respectively) when compared with control. Medicago polymorpha residues decomposed for 30 days exerted the greatest inhibitory effect on shoot fresh weight (46.1%) and root dry weight (59.9%). Vicia sativa with 30 days and T. polycerata residues without decomposition produced the least root fresh weight (65.3%) and shoot dry weight (52.6%), respectively. The root/shoot ratio (56.8%) was increased by T. polycerata residues without decomposition. Phenolics from leguminous weeds caused inhibition of germination/emergence and biomass partitioning in rice. Therefore, these weeds must be eradicated from the field at their initial growth stages.
Water and labour scarcity pushes researchers to explore alternate sowing methods for rice like ae... more Water and labour scarcity pushes researchers to explore alternate sowing methods for rice like aerobic direct seeding but weed infestation is the major hindrance to adapt this production system. In our study, mechanical, chemical and cultural approaches were employed as weed control measures. Weed dynamics and yield parameters were recorded and economic analysis was performed. All weed control measures significantly reduced the weed density and weed dry weight as compared to control and improved harvest index. Maximum control in total weed density and total weed dry weight was achieved by hoeing followed by chemical control. The order of treatment groups in decreasing total density, total weed dry matter production and increment in harvest index was as cultural, chemical and mechanical. However, substantially highest net returns (PKR 44,049/) and highest benefit cost ratio (BCR) (1.53) were obtained by post emergence application of Penuxsulam at the rate of 15 g a.i ha-1 followed by hoeing. Inter-culture, mulching technique and Sesbania drummondi intercropping scored 1.19, 1.13 and 1.21 BCR, respectively. Thus, hoeing with hoe (25 and 45 days after sowing) and post emergence application of Penoxsulamat the rate of 15 g a.i ha-1 were most effective, profitable and economical weed control options.
Allelopathic crops can provide organic alternative to manage herbicides resistant littleseed cana... more Allelopathic crops can provide organic alternative to manage herbicides resistant littleseed canarygrass (Phalaris minor Retz.) We used mulch of four potential allelopathic crops, including sorghum, maize, sunflower and rice at 0, 6, 9 and 12 tons ha-1 to manage herbicide resistant littleseed canarygrass. Repeated pot experiment was conducted under greenhouse at the Faculty of Agriculture, University of Agriculture, Faisalabad, Pakistan, from November, 2015 to March, 2016. Results revealed that significant inhibition in emergence percentage, shoot length, root length and dry biomass of littleseed canarygrass was observed three weeks after mulch application of four allelopathic crops. This inhibition was sustained with time and caused significant reduction in plant height, dry biomass, spike length and number of seeds produced per plant at maturity. Mulches of sorghum, maize, sunflower and rice at 12 tons ha-1 caused up to 38, 25, 29 and 41% inhibition in plant height, dry biomass, spike length and number of seeds per plant respectively. Weed control efficiency of four allelopathic crop mulches was ranging 20 to 25% at mulch dose of 12 tons ha-1. However, mulches at lower doses caused growth stimulation in few growth traits. On the base of this study we conclude that these allelopathic crop mulches can be used to control herbicide resistant littleseed canarygrass due to their strong phytotoxic potential and may provide basis to develop natural herbicides to control this grass.
Salt stress is one of major problem hampering plant growth and development to a significant level... more Salt stress is one of major problem hampering plant growth and development to a significant level. In present study, 5-aminolevulinic acid (ALA) was exogenously applied to Leymus chinensis (Trin.) Tzvel. plants at various concentrations (10, 50, and 100 mg L-1) to assess its effects on morphology, physiology, and biochemistry under salt stress conditions (150 mmol NaCl L-1) as compared with control. The results indicated that salt stress substantially impaired growth, physiology and biochemistry of L. chinensis plants; nonetheless, ALA application alleviated the adverse effects of salt stress. Application of ALA improved the leaf length, leaf area, leaf conductance, plant dry biomass, water contents, and root activity of L. chinensis under stress and no stress conditions. Additionally, biosynthesis of chlorophyll, carotenoids, free proline, soluble sugars and proteins of L. chinensis plants was also increased following ALA application as compared to control, under salt stress conditions. Moreover, we also observed an enhanced activity of antioxidant defense system in L. chinensis in response to ALA application. ALA elevated the activity of enzymatic antioxidants viz. ascorbate peroxidase (APX), glutathione reductase (GR), superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) significantly scavenged reactive oxygen species thus reduced the accumulation of malondialdehyde (MDA) under salt stress as compared to control under both normal and stressed conditions. The effect of ALA on all growth and biochemical attributes was concentration dependent and application of 50 as well as 100 mg L-1 ALA proved better. The results concluded that salt stress tolerance in L. chinensis plants can be increased by exogenously applied ALA at appropriate concentration. It was suggested that L. chinensis plants were treated with ALA application of 50-100 mg L-1 was more beneficial under both normal and saline conditions. ABSTRACT
Hormetic effects of herbicides at ultra-low doses have been proved against range of crop species,... more Hormetic effects of herbicides at ultra-low doses have been proved against range of crop species, although available data of herbicides hormesis about the weeds growth is very limited. This study investigates the promotive effect of low doses of fenoxaprop-Pethyl on growth and seed production of littleseed canarygrass and wild oat. Pot experiments were conducted twice in Wire House at Agronomic Research Area, University of Agriculture, Faisalabad, during 2014-15. Seven different concentrations of fenoxaprop-P-ethyl [0, 1, 3, 6, 9, 12 and 15 g a.i. ha-1] were applied as post emergence herbicide at 3-4 leaves stage of the weeds. Results revealed that increase in growth occurred within first two weeks after spraying at fenoxaprop-P-ethyl doses 1, 3 and 6 g a.i. ha-1. More growth stimulation as compared to all other treatments was observed at fenoxaprop-P-ethyl dose 6 g a.i. ha-1. This initial increase in growth sustains with time up to the maturity of both weeds and positively influences seeds production ability. Up to 28% and 17% increase in number of seeds per plants were occurred in littleseed canarygrass and wild oat, respectively. Doses above 6 g a.i. ha-1 negatively affect the weeds growth and seed production ability.
Little is known of glyphosate-caused hormesis in weeds and how this might influence weed manageme... more Little is known of glyphosate-caused hormesis in weeds and how this might influence weed management. To test the hormetic effect of low doses of glyphosate on broad-leaved weeds, two experiments were conducted in laboratory and screenhouse. Hormetic effects of glyphosate solution in growth media (0, 65, 130, 250 and 500 g acid equivalent (a.e) ha-1) and foliar spray (0, 4, 8, 16, 32 and 64 g a.e. ha-1) were tested on four broad-leaved weeds (Coronopus didymus, Chenopodium album, Rumex dentatus and Lathyrus aphaca). Glyphosate solutions in range of 65-250 g a.e. ha-1 stimulated the germination and seedling growth of all tested weeds. However, at 500 g a.e. ha-1 germination and growth inhibition was observed. Foliar applied glyphosate at range of 4-32 g a.e. ha-1 increased the root and shoot length, dry biomass and seed production ability of all four weeds species. However, the stimulatory response was species dependent. These results indicate that glyphosate hormesis could play a significant role in altering crop/weed competition and might influence weed management.
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crop plants through the release of their allelochemicals and hence seriously reduce crop productivity. The present study was conducted to investigate the allelopathic effect of water soluble phenolics of weeds associated with wheat crop (Vicia sativa, Trigonella polycerata, Lathyrus aphaca, Medicago polymorpha, Melilotus indica) on germinability and biomass production of wheat seedlings by using their water extracts at 2.5% (w/v) and 5% (w/v) concentrations and residues of the same weeds with 0, 15 and 30 d decomposition periods at 2% (w/w) concentration. The results showed that the water extracts of M. indica and V. sativa at 5% concentration imposed the most inhibitory effect on energy of germination (81%) and prolonged time to 50% germination (226%), respectively; by contrast, T. polycerata and M. indica extracts at the same concentration inhibited shoot (8%) and root fresh biomass (64%). However, shoot dry biomass was exalted by the weed extracts at both concentrations with maximum increase (29%) caused by the M. indica extract at 2.5% concentration; however, root dry biomass (46%) and root/shoot ratio (51%) were decreased by M. polymorpha and M. indica extracts at 5% concentration, respectively. Residues of L. aphaca and M. polymorpha with a 30 d decomposition period proved the most
toxic regarding energy of emergence (85%) and time to 50% emergence (138%), respectively; while, shoot fresh (41%) and dry biomass (26%) production were hindered mostly by M. indica and M. polymorpha residues with a 30 d decomposition period. There was the highest decrease in root fresh (64%) and dry biomass (64%), and root/shoot ratio (64%) when treatment was performed with V. sativa residues without decomposition. The results show that leachates and residues of weeds inhibit wheat germinability and biomass production through release of allelochemicals, and they are a threat to profitable crop production.
stage (BBCH growth stage 49) and was maintained till physiological maturity (BBCH growth stage 83). Seeds of bread wheat, collected from crop raised under terminal drought and/or well-watered conditions, were subjected to hydropriming and osmopriming (with 1.5% CaCl2) and were sown in soil-filled pots. After stand establishment, salt stress treatments viz. 10 mM NaCl (control) and 100 mM NaCl were imposed. Seed from terminal drought stressed source had less fat (5%), and more fibers (11%), proteins (22%) and total soluble phenolics (514%) than well-watered seed source. Salt stress reduced the plant growth, perturbed water relations and decreased yield. However, an increase in osmolytes accumulation (4-18%), malondialdehyde (MDA) (27-35%) and tissue Na contents (149-332%) was observed under salt stress. The seeds collected from drought stressed crop had better tolerance against salt stress as indicated by better yield (28%), improved water relations (3-18%), osmolytes accumulation (21-33%), and less MDA (8%) and Na contents (35%) than progeny of well-watered crop. Seed priming, osmopriming in particular, further improved the tolerance against salt stress through improvement in leaf area, water relations, leaf proline, glycine betaine and grain yield while lowering MDA and Na contents. In conclusion, changed seed composition during terminal drought and seed priming improved the salt tolerance in wheat by modulating the water relations, osmolytes accumulation and lipid peroxidation.
foliar-applied nutrients (nitrogen, phosphorus, potassium: NPK) and 5-aminolevulinic acid (ALA) alone and in combination on morpho-physiological indices of the perennial grass Leymus chinensis (Trin.) Tzvel under drought and well-watered conditions. Drought stress caused a reduction in growth and photosynthetic pigments while increasing the accumulation of malondialdehyde (MDA) and osmolytes compared with well-watered conditions. However, application of NPK and ALA improved plant height, fresh and dry weights, and chlorophyll content. Production of soluble proteins and sugars, proline content, and antioxidant enzyme activities (superoxide dismutase, peroxidase, catalase, ascorbate peroxidase and glutathione reductase) were increased and MDA accumulation was lowered by application of NPK and ALA relative to
the control (no application). Combined application of NPK and ALA proved more advantageous than NPK or ALA alone in exerting ameliorative effect on L. chinensis under drought-stressed conditions. The results suggest that combined application of NPK and ALA improves the growth and development of L. chinensis by modulating physiological processes and aids in sustaining drought.
of water extracts at varying concentrations (2.5% and 5% w/v) and residues with varying decomposition periods (0, 15 and 30 days) at 2% (w/w) concentration of four weeds (Trigonella polycerata, Vicia sativa, Lathyrus aphaca, Medicago polymorpha) against rate, synchronization and time of germination, and biomass partitioning of rice through plant and soil bioassays. Germination and biomass partitioning in rice plants were inhibited by extracts and residues. The maximum decrease in energy of germination (88.6%) and increase in time for 50% germination
(210.4%) were caused by the L. aphaca extract at 5% concentration as compared to control. Root and shoot, fresh weight (13.6 and 28.6%, respectively) and dry weight (20.4 and 41.7%, respectively) were reduced by the M. polymorpha extract at 5% concentration. The Vicia sativa extract at both concentrations caused a great increase in the root/shoot ratio (125-145.8%). Trigonella polycerata and V. sativa residues
decomposed for 30 days caused maximum inhibition of energy of emergence (71.4%) and their decomposition for zero and 15 days, respectively, inhibited coefficient of uniformity of emergence (78.9%). Medicago polymorpha and L. aphaca residues decomposed for 30 days exaggerated time for 50% emergence (47.1 and 50.3%, respectively) when compared with control. Medicago polymorpha residues decomposed for 30 days exerted the greatest inhibitory effect on shoot fresh weight (46.1%) and root dry weight (59.9%). Vicia sativa with 30 days and T. polycerata residues without decomposition produced the least root fresh weight (65.3%) and shoot dry weight (52.6%), respectively. The root/shoot ratio (56.8%) was increased by T. polycerata residues without decomposition. Phenolics from leguminous weeds
caused inhibition of germination/emergence and biomass partitioning in rice. Therefore, these weeds must be eradicated from the field at their initial growth stages.
were conducted twice in Wire House at Agronomic Research Area, University of Agriculture, Faisalabad, during 2014-15. Seven different concentrations of fenoxaprop-P-ethyl [0, 1, 3, 6, 9, 12 and 15 g a.i. ha-1] were applied as post emergence herbicide at 3-4 leaves stage of the
weeds. Results revealed that increase in growth occurred within first two weeks after spraying at fenoxaprop-P-ethyl doses 1, 3 and 6 g a.i. ha-1. More growth stimulation as compared to all other treatments was observed at fenoxaprop-P-ethyl dose 6 g a.i. ha-1. This initial increase
in growth sustains with time up to the maturity of both weeds and positively influences seeds production ability. Up to 28% and 17% increase in number of seeds per plants were occurred in littleseed canarygrass and wild oat, respectively. Doses above 6 g a.i. ha-1 negatively affect the weeds growth and seed production ability.
glyphosate solution in growth media (0, 65, 130, 250 and 500 g acid equivalent (a.e) ha-1) and foliar spray (0, 4, 8, 16, 32 and 64 g a.e. ha-1) were tested on four broad-leaved weeds (Coronopus didymus, Chenopodium album, Rumex dentatus and Lathyrus aphaca).
Glyphosate solutions in range of 65-250 g a.e. ha-1 stimulated the germination and seedling growth of all tested weeds. However, at 500 g a.e. ha-1 germination and growth inhibition was observed. Foliar applied glyphosate at range of 4-32 g a.e. ha-1 increased the root and shoot
length, dry biomass and seed production ability of all four weeds species. However, the stimulatory response was species dependent. These results indicate that glyphosate hormesis could play a significant role in altering crop/weed competition and might influence weed
management.
crop plants through the release of their allelochemicals and hence seriously reduce crop productivity. The present study was conducted to investigate the allelopathic effect of water soluble phenolics of weeds associated with wheat crop (Vicia sativa, Trigonella polycerata, Lathyrus aphaca, Medicago polymorpha, Melilotus indica) on germinability and biomass production of wheat seedlings by using their water extracts at 2.5% (w/v) and 5% (w/v) concentrations and residues of the same weeds with 0, 15 and 30 d decomposition periods at 2% (w/w) concentration. The results showed that the water extracts of M. indica and V. sativa at 5% concentration imposed the most inhibitory effect on energy of germination (81%) and prolonged time to 50% germination (226%), respectively; by contrast, T. polycerata and M. indica extracts at the same concentration inhibited shoot (8%) and root fresh biomass (64%). However, shoot dry biomass was exalted by the weed extracts at both concentrations with maximum increase (29%) caused by the M. indica extract at 2.5% concentration; however, root dry biomass (46%) and root/shoot ratio (51%) were decreased by M. polymorpha and M. indica extracts at 5% concentration, respectively. Residues of L. aphaca and M. polymorpha with a 30 d decomposition period proved the most
toxic regarding energy of emergence (85%) and time to 50% emergence (138%), respectively; while, shoot fresh (41%) and dry biomass (26%) production were hindered mostly by M. indica and M. polymorpha residues with a 30 d decomposition period. There was the highest decrease in root fresh (64%) and dry biomass (64%), and root/shoot ratio (64%) when treatment was performed with V. sativa residues without decomposition. The results show that leachates and residues of weeds inhibit wheat germinability and biomass production through release of allelochemicals, and they are a threat to profitable crop production.
stage (BBCH growth stage 49) and was maintained till physiological maturity (BBCH growth stage 83). Seeds of bread wheat, collected from crop raised under terminal drought and/or well-watered conditions, were subjected to hydropriming and osmopriming (with 1.5% CaCl2) and were sown in soil-filled pots. After stand establishment, salt stress treatments viz. 10 mM NaCl (control) and 100 mM NaCl were imposed. Seed from terminal drought stressed source had less fat (5%), and more fibers (11%), proteins (22%) and total soluble phenolics (514%) than well-watered seed source. Salt stress reduced the plant growth, perturbed water relations and decreased yield. However, an increase in osmolytes accumulation (4-18%), malondialdehyde (MDA) (27-35%) and tissue Na contents (149-332%) was observed under salt stress. The seeds collected from drought stressed crop had better tolerance against salt stress as indicated by better yield (28%), improved water relations (3-18%), osmolytes accumulation (21-33%), and less MDA (8%) and Na contents (35%) than progeny of well-watered crop. Seed priming, osmopriming in particular, further improved the tolerance against salt stress through improvement in leaf area, water relations, leaf proline, glycine betaine and grain yield while lowering MDA and Na contents. In conclusion, changed seed composition during terminal drought and seed priming improved the salt tolerance in wheat by modulating the water relations, osmolytes accumulation and lipid peroxidation.
foliar-applied nutrients (nitrogen, phosphorus, potassium: NPK) and 5-aminolevulinic acid (ALA) alone and in combination on morpho-physiological indices of the perennial grass Leymus chinensis (Trin.) Tzvel under drought and well-watered conditions. Drought stress caused a reduction in growth and photosynthetic pigments while increasing the accumulation of malondialdehyde (MDA) and osmolytes compared with well-watered conditions. However, application of NPK and ALA improved plant height, fresh and dry weights, and chlorophyll content. Production of soluble proteins and sugars, proline content, and antioxidant enzyme activities (superoxide dismutase, peroxidase, catalase, ascorbate peroxidase and glutathione reductase) were increased and MDA accumulation was lowered by application of NPK and ALA relative to
the control (no application). Combined application of NPK and ALA proved more advantageous than NPK or ALA alone in exerting ameliorative effect on L. chinensis under drought-stressed conditions. The results suggest that combined application of NPK and ALA improves the growth and development of L. chinensis by modulating physiological processes and aids in sustaining drought.
of water extracts at varying concentrations (2.5% and 5% w/v) and residues with varying decomposition periods (0, 15 and 30 days) at 2% (w/w) concentration of four weeds (Trigonella polycerata, Vicia sativa, Lathyrus aphaca, Medicago polymorpha) against rate, synchronization and time of germination, and biomass partitioning of rice through plant and soil bioassays. Germination and biomass partitioning in rice plants were inhibited by extracts and residues. The maximum decrease in energy of germination (88.6%) and increase in time for 50% germination
(210.4%) were caused by the L. aphaca extract at 5% concentration as compared to control. Root and shoot, fresh weight (13.6 and 28.6%, respectively) and dry weight (20.4 and 41.7%, respectively) were reduced by the M. polymorpha extract at 5% concentration. The Vicia sativa extract at both concentrations caused a great increase in the root/shoot ratio (125-145.8%). Trigonella polycerata and V. sativa residues
decomposed for 30 days caused maximum inhibition of energy of emergence (71.4%) and their decomposition for zero and 15 days, respectively, inhibited coefficient of uniformity of emergence (78.9%). Medicago polymorpha and L. aphaca residues decomposed for 30 days exaggerated time for 50% emergence (47.1 and 50.3%, respectively) when compared with control. Medicago polymorpha residues decomposed for 30 days exerted the greatest inhibitory effect on shoot fresh weight (46.1%) and root dry weight (59.9%). Vicia sativa with 30 days and T. polycerata residues without decomposition produced the least root fresh weight (65.3%) and shoot dry weight (52.6%), respectively. The root/shoot ratio (56.8%) was increased by T. polycerata residues without decomposition. Phenolics from leguminous weeds
caused inhibition of germination/emergence and biomass partitioning in rice. Therefore, these weeds must be eradicated from the field at their initial growth stages.
were conducted twice in Wire House at Agronomic Research Area, University of Agriculture, Faisalabad, during 2014-15. Seven different concentrations of fenoxaprop-P-ethyl [0, 1, 3, 6, 9, 12 and 15 g a.i. ha-1] were applied as post emergence herbicide at 3-4 leaves stage of the
weeds. Results revealed that increase in growth occurred within first two weeks after spraying at fenoxaprop-P-ethyl doses 1, 3 and 6 g a.i. ha-1. More growth stimulation as compared to all other treatments was observed at fenoxaprop-P-ethyl dose 6 g a.i. ha-1. This initial increase
in growth sustains with time up to the maturity of both weeds and positively influences seeds production ability. Up to 28% and 17% increase in number of seeds per plants were occurred in littleseed canarygrass and wild oat, respectively. Doses above 6 g a.i. ha-1 negatively affect the weeds growth and seed production ability.
glyphosate solution in growth media (0, 65, 130, 250 and 500 g acid equivalent (a.e) ha-1) and foliar spray (0, 4, 8, 16, 32 and 64 g a.e. ha-1) were tested on four broad-leaved weeds (Coronopus didymus, Chenopodium album, Rumex dentatus and Lathyrus aphaca).
Glyphosate solutions in range of 65-250 g a.e. ha-1 stimulated the germination and seedling growth of all tested weeds. However, at 500 g a.e. ha-1 germination and growth inhibition was observed. Foliar applied glyphosate at range of 4-32 g a.e. ha-1 increased the root and shoot
length, dry biomass and seed production ability of all four weeds species. However, the stimulatory response was species dependent. These results indicate that glyphosate hormesis could play a significant role in altering crop/weed competition and might influence weed
management.