Drought Stress

Summary. In this study, calli were obtained from in vitro grown potato stem or leaf segments cv. Cosima on MS medium containing 2,4-D, NAA, kinetin and yeast extract. After three subcultures, well grown calli were exposed to UV-C radiation with approximately 6.24 µmol photon/m2/s for 30 min three times at an interval of 2 weeks. Somaclonal variation induced by UV-C

Drought stress at grain filling is the prominent and inevitable characteristic of arid and semi-arid areas. The objectives of this research were to determine the effect of drought stress and the role of current of assimilates on grain filling, storage capacity and contribution of stem reserves to the growing grains. Therefore, an experiment was carried out in a split-plot factorial arranged in a randomized complete blocks design with three replications during 2010-2011 season cropping cycle in research farm of Razi University in Iran. The moisture regimes were well watered (non-water stress) and drought stressed (post-anthesis water deficiency with withholding of irrigation and continued until physiological maturity). The barley cultivars (Hordeum vulgare L.) including Aras, Afzal, Jonub, Reihan, Zarjo, Sararud, Sahra, Fajr-30, Karoun, Gorgan-4, Makuei and Nosrat, also the source manipulation treatments including control, defoliation of flag leaf, defoliation of all leaves except the flag leaf, de-awning and ear shaded were imposed at anthesis. The results showed that, grain yield (GY) was reduced by 20.7% under drought due to 9.8 and 15.3% reduction in thousand grain weight (TGW) and number of grains per spike (NGS), respectively. Under removing of assimilate sources, remobilization of stored material from the stem internodes was increased and these results suggest the compensatory role of different part of stem in preventing yield loss. Drought stress could not increase the remobilization efficiency (RE), but in terms of mentioned traits, there were significant differences between cultivars and different removing photosynthetic sources. Cultivars with longer internodes had greater amounts of photo-assimilates in different parts of the stem and also higher amount of remobilization to the growing grains than in comparison to cultivars with shorter internodes. In both well water and drought stress treatments, the amounts of remobilization from different parts of stem to the growing grains were similar, but under well watered condition due to higher photosynthesis rate compare to drought stress condition, GY was higher.

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,...

Sunflower (Helianthus annuus L.) sustains frequently into severe droughts in recent years due to global warming as a spring crop. These abiotic stress affects seed yield highly resulting important yield loses as well as in oil yield in sunflower because especially the hot temperatures during grain filling period firstly reduce water quickly in the seed with resulting empty kernels. Therefore, sunflower breeders screen genotypes for searching drought tolerant genes in their sunflower breeding programs frequently to develop drought tolerant hybrids because only tolerant ones which have higher adaption capability to dry areas could be planted widely in the next years. The study was conducted in under controlled environmental conditions in Trakya Agricultural Research Institute, Edirne Turkey where is in Trakya Region which is European part of Turkey has about 50% of Turkish sunflower production areas growing in rain fed conditions. Some phenological and yield traits as well as total chlorophyll contents of some sunflower male inbred lines at R3, R5-1 and R6 growing periods as three drought stress applications were examined in the study. Correlation and regression analysis were performed to determine the relationships between seed yield and other yield traits. Based on correlation study results, the significant relationships were observed between seed yield per head and other yield traits (plant height, head diameter, leaf number and area, oil content and yield and thousand seed weights) in sunflower male lines both in control and three stress conditions except total Chlorophyll content in stress conditions. There are significant linear and quadratic relationships between seed yield and other yield traits based on regression analysis results in the study. The relationships of yield traits in this drought tolerance research will associate in sunflower breeding program then it will help starting to develop drought tolerant genotypes for future to escape away from drought stress in global warming conditions.

The global population is increasing at an alarming rate. Meeting food and nutritional demand of this increased population has become a major issue for agronomist and agricultural researchers. On the top of that, overall agricultural productions are constrained by global climate change resulting several biotic and abiotic stress. Among the abiotic stress, drought has become a problematic issues in arid and semi-arid regions of the world leading towards the dire future, questioning on food sufficiency and affordability for future world. Though several adaptation and mitigation strategies are practiced at local and global level, these seems redundant with increased demand of foods crops. To address the problem of climate change on drought in a sustainable way, climate ready crops are been developed through selection, breeding and genetic engineering techniques. These crops are tailored for drought prone areas pooling all the traits that are responsible for tolerating the water stress condition. This review article discuss some of the released climate ready crops, their xerophytic traits and mechanism of gene expression of such crops. Climate ready crops seems to surpass the effect of climate change on drought stress through sustained productivity that could meet the need of future generation. Development and management of these crops could help to maintain the stability on food production that could become a real boon for agriculture which is hindered by climate change.

Scarcity of water is a severe environmental constraint to plant productivity. Drought-induced loss in crop yield probably exceeds losses from all other causes, since both the severity and duration of the stress are critical. Here, we have reviewed the effects of drought stress on the growth, phenology, water and nutrient relations, photosynthesis, assimilate partitioning, and respiration in plants. This article also describes the mechanism of drought resistance in plants on a morphological, physiological and molecular basis. Various management strategies have been proposed to cope with drought stress. Drought stress reduces leaf size, stem extension and root proliferation, disturbs plant water relations and reduces water-use efficiency. Plants display a variety of physiological and biochemical responses at cellular and whole-organism levels towards prevailing drought stress, thus making it a complex phenomenon. CO2 assimilation by leaves is reduced mainly by stomatal closure, membrane damage and disturbed activity of various enzymes, especially those of CO2 fixation and adenosine triphosphate synthesis. Enhanced metabolite flux through the photorespiratory pathway increases the oxidative load on the tissues as both processes generate reactive oxygen species. Injury caused by reactive oxygen species to biological macromolecules under drought stress is among the major deterrents to growth. Plants display a range of mechanisms to withstand drought stress. The major mechanisms include curtailed water loss by increased diffusive resistance, enhanced water uptake with prolific and deep root systems and its efficient use, and smaller and succulent leaves to reduce the transpirational loss. Among the nutrients, potassium ions help in osmotic adjustment; silicon increases root endodermal silicification and improves the cell water balance. Low-molecular-weight osmolytes, including glycinebetaine, proline and other amino acids, organic acids, and polyols, are crucial to sustain cellular functions under drought. Plant growth substances such as salicylic acid, auxins, gibberrellins, cytokinin and abscisic acid modulate the plant responses towards drought. Polyamines, citrulline and several enzymes act as antioxidants and reduce the adverse effects of water deficit. At molecular levels several drought-responsive genes and transcription factors have been identified, such as the dehydration-responsive element-binding gene, aquaporin, late embryogenesis abundant proteins and dehydrins. Plant drought tolerance can be managed by adopting strategies such as mass screening and breeding, marker-assisted selection and exogenous application of hormones and osmoprotectants to seed or growing plants, as well as engineering for drought resistance.

Abstract
  Attention has been growing recently in the water problems in the world, and the urgent need to write a scientific book on water resources in the province of Basra in particular because it is the most severe spot drought in the world,
The problems of water in Basra are multiple and rooted and have a temporal dimension (political and social complex), so there is a need to disassemble and analyze the scientific resources available from the water wealth, and design features conducive to finding practical solutions to possible problems, and the book presents a summary of research experience and personal coexistence researcher with the hydrological situation in In the south of Iraq during several different periods witnessed a striking disparity between the abundance of water and scarcity, and the prospect of the near future confirmed the scarcity of drought-prone, also to develop possible solutions to address the reality of water deteriorating in Basra, the book included fourteen chapters of the scientific view of the hydrological situation The book also included an explanation of the implemented water projects and proposals for the integrated management of water resources, streams and channels, and innovative ideas for the transformation of the main freshwater transporters to be less extensive and the most important design of the channels (Al-Bida'a and Kteeban Canals), and to benefit from the flow of sea water in the Shatt al-Arab and co-exist with it, and to develop a new vision to deal with the waters of the Tigris and Euphrates Rivers in the central and southern areas in the introduction of sustainable agricultural and pastoral varieties. Reducing waste and depletion to cope with climate change and increasing reservoir and irrigation projects, as well as preparing for the expected water shortages and the deterioration of their quality, and planning for traditional water alternatives by using Gulf water resources that are permanent water and non-traditional resources that meet some of the population's needs. In Basra, the authors made recommendations on the development of economic activities such as aquaculture, power generation, transport, fishing and tourism.

We present new remote sensing indices of plant water status: the ratio between the reflectance at 970 nm, one of the water absorption bands, and the reflectance at a reference wavelength, 900 nm (R970/R9000; the first derivative minimum in this near-infrared region (dNIRminimum) and the wavelength where this minimum is found ( λNIRminimum). In order to evaluate them, we carried out three experiments. Daily irrigated gerbera plants were allowed to dry until almost wilting and then daily irrigation was restarted; pepper and bean plants were grown for four months submitted to two different irrigation treatments; and bean detached leaves were submitted to progressive dehydration whereas pressure-volume curves were being carried out.In gerbera plants, the trough about 950–970 nm decreased as the drought was increasing. Therefore, the R970/R900 index and the dNIRminimum closely tracked the changes in relative water content (RWC), leaf water potential, stomatal conductance and the foliage-air temperature differences. The λdNIRminimum tracked even better these changes in gerberas. However, these water status indices began to be significant when the water stress was already well developed, at RWC smaller than 85 per cent. The same happened to detached leaves of beans which did not present differences above −1·55 MPa water potential. Beans and peppers growing at soil matric potentials larger than −0·04 MPa presented higher R970/R900 values than those growing at soil matric potentials only larger than −0·01 MPa.In all the cases, the maximum response of these indices was found in the varieties or the species that lost cell wall elasticity in response to drought stress. This could indicate an important structural component in these indices changes. Relative water content itself seemed to be, however, the most important factor as shown by the highest correlation coefficients with these spectral indices. These spectral signals were more evident at canopy level than at leaf level. They seem to be useful as water status indicators at ground level, especially when there are not important changes of LAI and when plants wholly cover the soil.

Scarcity of water is a severe environmental constraint to plant productivity. Drought-induced loss in crop yield probably exceeds losses from all other causes, since both the severity and duration of the stress are critical. Here, we have reviewed the effects of drought stress on the growth, phenology, water and nutrient relations, photosynthesis, assimilate partitioning, and respiration in plants. This article also describes the mechanism of drought resistance in plants on a morphological, physiological and molecular basis. Various management strategies have been proposed to cope with drought stress. Drought stress reduces leaf size, stem extension and root proliferation, disturbs plant water relations and reduces water-use efficiency. Plants display a variety of physiological and biochemical responses at cellular and whole-organism levels towards prevailing drought stress, thus making it a complex phenomenon. CO2 assimilation by leaves is reduced mainly by stomatal closure, membrane damage and disturbed activity of various enzymes, especially those of CO2 fixation and adenosine triphosphate synthesis. Enhanced metabolite flux through the photorespiratory pathway increases the oxidative load on the tissues as both processes generate reactive oxygen species. Injury caused by reactive oxygen species to biological macromolecules under drought stress is among the major deterrents to growth. Plants display a range of mechanisms to withstand drought stress. The major mechanisms include curtailed water loss by increased diffusive resistance, enhanced water uptake with prolific and deep root systems and its efficient use, and smaller and succulent leaves to reduce the transpirational loss. Among the nutrients, potassium ions help in osmotic adjustment; silicon increases root endodermal silicification and improves the cell water balance. Low-molecular-weight osmolytes, including glycinebetaine, proline and other amino acids, organic acids, and polyols, are crucial to sustain cellular functions under drought. Plant growth substances such as salicylic acid, auxins, gibberrellins, cytokinin and abscisic acid modulate the plant responses towards drought. Polyamines, citrulline and several enzymes act as antioxidants and reduce the adverse effects of water deficit. At molecular levels several drought-responsive genes and transcription factors have been identified, such as the dehydration-responsive element-binding gene, aquaporin, late embryogenesis abundant proteins and dehydrins. Plant drought tolerance can be managed by adopting strategies such as mass screening and breeding, marker-assisted selection and exogenous application of hormones and osmoprotectants to seed or growing plants, as well as engineering for drought resistance.

Two durum wheat (Triticum durum Desf.) cultivars were tested for salt and drought tolerance at germination, seedling emergence and early seedling growth in NaCl and PEG-8000 solutions of different osmotic potentials (–0.2, –0.4, –0.6 and –0.8 MPa). Daily and final germination and emergence percentage, as well as germination and seedling emergence rate, seedling growth, fresh and dry weight were recorded under controlled conditions. Results showed that germination and emergence rates were delayed by both solutions in both cultivars, but Omrabia showed higher germination and emergence rates than BD290273 in NaCl while BD290273 was less affected by NaCl and PEG solutions at the emergence stage. Sodium chloride had a lesser effect on both cultivars in terms of germination rate, emergence rate, final germination and emergence percentage than did PEG-8000. This conclusively proves that the adverse effect of PEG-8000 on germination, emergence and early seedling growth was due to the osmoti...

The evaluation of physiological and biochemical aspects is essential to identify clues that can assist breeders in selecting Persian walnut genotypes with considerable tolerance to drought stress. This objective can be obtained by analyzing seed biochemical compounds from different genetic resources, e.g. seeds from individual trees that are commonly exposed to drought stress. In the current research, we evaluated the effects of drought stress, as induced by PEG6000, on the germination of walnut seeds collected from six promising genotypes (i.e. 'SS2', 'TT2', 'TT1', 'ZM1','Haward' and'Chandler'). Aphotoperiod of12hwas provided duringtheexperiments, alongwithan average temperature of 25 ± 1°C. According to the different indexes of germination, a greater tolerance was observed among three genotypes, namely, 'ZM1', 'Haward' and ‘Chandler’. In response to drought stress, the contents of proline and total soluble sugars increased, especially at intense levels of stress, whereas the amount of starch decreased. The levels of antioxidant activity significantly increased by POD, APX, CAT, SOD and LOX enzymes in the radicle and plumule tissues as the water potential reached −1.5MPa. Three genotypes, namely, 'TT2', 'TT1' and 'SS2'were susceptible to cell wall damage(i.e. bylipid peroxidation). High levels ofSpdand Spm in tolerant genotypes were accompanied by significant increases in the zeatin, endogenous IAA, zeatin riboside and ABA in the seeds. Our results suggest that, under drought stress, seed germination in walnuts can benefit from the accumulation of free Spd in seeds during the phases of germination. However, the accumulation of free Put appeared to be an inhibitory factor which suppressed the germination of walnut seeds.

Building resilience to extreme events is very complex. It involves consideration of climatic and non-climatic factors, human and natural environments and their dynamics, and governance systems that include groups with wide-ranging authorities, influence and interests. In this article, we analyse the effects of the latest multi-year drought (2011–2016) in agricultural production in California; impacts on food security; and coping responses of several actors. We found that despite the drought and water shortages, California continued to be the leading state for fruit and tree nuts and that it did not affect food security. We also found that these results were strongly influenced by the numerous policy, regulatory, institutional, and management decisions taken at the local, state and federal levels, as well as to availability of groundwater, the primary drought reserve. The California case can be considered an example for the rest of the country, and the world, that extreme events require extraordinary preparedness and response measures just to cope with them, not to mention adapting to them, and that building resilience is a long-term process.

In the southern spring–summer season of 2001–2002 six cultivars (Orfeo, Arroz Tuscola, Barbucho, Coscorrón, Pinto and Tórtola) of common beans (Phaseolus vulgaris L.) were grown under two frequencies of irrigation in the central zone of Chile. Control plants were irrigated every 7 days and water stress plants were irrigated every 21 days. Leaf water potential (ΨW), leaf relative water content (RWC), turgid weight to dry weight ratio (TW/DW), osmotic potential at full turgor (ψS100), osmotic adjustment (OA), elasticity module of the cell wall (ɛ) and cell size of the palisade and spongy tissue were evaluated at 74–76 days after sowing (DAS) in completely developed leaves. Water stressed plants showed lower ΨW than in control plants in all the varieties with values that averaged −1.4 and −0.9 MPa, respectively. According to the Drought Resistance Index (DRI) calculated from field measurements, among the cultivars studied, Orfeo was the most resistant to water stress and Arroz Tuscola, the most susceptible. A close negative relationship between leaf TW/DW and DRI under water stress conditions was observed (r2 = 0.63). Leaf TW/DW decreased considerably with water stress in cultivar Orfeo (15%) but the decrease was higher in Tórtola (22%), and there was also a decrease (although smaller) in Pinto (11%). Arroz Tuscola under stress did not present an important change in TW/DW, but presented one of the highest values of TW/DW. There was a strong negative correlation between DRI and palisade cell size under water stress conditions (r2 = 0.85) and a strong positive one between palisade cell size and TW/DW (r2 = 0.86) thus higher DRI was associated with small palisade cell size and small TW/DW. The most resistant cultivar Orfeo did not show a decrease in ψS100 calculated from the pressure–RWC relationships and its resistance was not associated with maintenance of leaf TW/DW under water stress. ψS100 calculated from the pressure–RWC relationships decreased only in the cultivar Coscorrón. Cultivar Orfeo showed a strong decrease (35%) of ɛ, in association to a higher cell wall elasticity (CWE) and as consequence maintained better its cell turgescence but this was also the case of Tórtola (56%) and Pinto (34%) and to a lesser extent of Barbucho (18%). This was not the case for Arroz Tuscola where ɛ and CWE were not changed. These results suggest that CWE and to a lesser extent leaf TW/DW can be important components of the water stress adaptation mechanism in this specie that could contribute to the higher resistance to water stress of Orfeo compared to Arroz Tuscola.

This review presents general information about Hohoba commonly as jojoba. It is the sole species of the family Simmondsiaceae. Jojoba plants have currently received exceptional attention, since, its seeds contain a unique liquid wax commonly called jojoba oil, that is very similar to that obtained from Whale sperm. Jojoba is considered a promising crop for arid and marginal areas; the plant also has probable value in combatting desertification and soil degradation in dry areas. Although the plant is known for its high-temperature and high-salinity tolerance growth ability, jojoba considered as a new plant for arid and marginal areas.The plant is grown for its seed which contains a liquid wax with a high melting point. This oil is used in a variety of products including pharmaceuticals, cosmetics, lubricants and bio-fuel. Several aspects of the crop agronomy is reviewed including a botanical description, propagation methods from seed and cuttings, This review is intended to afford a reference to scientists and growers in the agronomy and management of jojoba.

Scarcity of water is a severe environmental constraint to plant productivity. Drought-induced loss in crop yield probably exceeds losses from all other causes, since both the severity and duration of the stress are critical. Here, we have reviewed the effects of drought stress on the growth, phenology, water and nutrient relations, photosynthesis, assimilate partitioning, and respiration in plants. This article also describes the mechanism of drought resistance in plants on a morphological, physiological and molecular basis. Various management strategies have been proposed to cope with drought stress. Drought stress reduces leaf size, stem extension and root proliferation, disturbs plant water relations and reduces water-use efficiency. Plants display a variety of physiological and biochemical responses at cellular and whole-organism levels towards prevailing drought stress, thus making it a complex phenomenon. CO2 assimilation by leaves is reduced mainly by stomatal closure, membrane damage and disturbed activity of various enzymes, especially those of CO2 fixation and adenosine triphosphate synthesis. Enhanced metabolite flux through the photorespiratory pathway increases the oxidative load on the tissues as both processes generate reactive oxygen species. Injury caused by reactive oxygen species to biological macromolecules under drought stress is among the major deterrents to growth. Plants display a range of mechanisms to withstand drought stress. The major mechanisms include curtailed water loss by increased diffusive resistance, enhanced water uptake with prolific and deep root systems and its efficient use, and smaller and succulent leaves to reduce the transpirational loss. Among the nutrients, potassium ions help in osmotic adjustment; silicon increases root endodermal silicification and improves the cell water balance. Low-molecular-weight osmolytes, including glycinebetaine, proline and other amino acids, organic acids, and polyols, are crucial to sustain cellular functions under drought. Plant growth substances such as salicylic acid, auxins, gibberrellins, cytokinin and abscisic acid modulate the plant responses towards drought. Polyamines, citrulline and several enzymes act as antioxidants and reduce the adverse effects of water deficit. At molecular levels several drought-responsive genes and transcription factors have been identified, such as the dehydration-responsive element-binding gene, aquaporin, late embryogenesis abundant proteins and dehydrins. Plant drought tolerance can be managed by adopting strategies such as mass screening and breeding, marker-assisted selection and exogenous application of hormones and osmoprotectants to seed or growing plants, as well as engineering for drought resistance.