Elevated CO2 modulates the effects of drought and heat stress on plant water relations and grain yield in wheat

To investigate the interactive effects of drought, heat and elevated atmospheric CO₂ concentration ([CO₂]) on plant water relations and grain yield in wheat, two wheat cultivars with different drought tolerance (Gladius and Paragon) were grown under ambient and elevated [CO₂], and were exposed to post‐anthesis drought and heat stress. The stomatal conductance, plant water relation parameters, abscisic acid concentration in leaf and spike, and grain yield components were examined. Both stress treatments and elevated [CO₂] reduced the stomatal conductance, which resulted in lower leaf relative water content and leaf water potential. Drought induced a significant increase in leaf and spike abscisic acid concentrations, while elevated [CO₂] showed no effect. At maturity, post‐anthesis drought and heat stress significantly decreased the grain yield by 21.3%–65.2%, while elevated [CO₂] increased the grain yield by 20.8% in wheat, which was due to the changes of grain number per spike and thousand grain weight. This study suggested that the responses of plant water status and grain yield to extreme climatic events (heat and drought) can be influenced by the atmospheric CO₂ concentration.     

Methyl Jasmonate‐Induced Alteration in Lipid Peroxidation,Antioxidative Defence System and Yield in Soybean Under Drought

Methyl jasmonate (MeJA), a plant‐signalling molecule, is involved in an array of plant development and the defence responses. This study was conducted to explore the role of exogenous MeJA application in alleviating the adversities of drought stress in soybean (Glycine max L. Merrill.). Soybean plants were grown under normal conditions until blooming and were then subjected to drought by withholding irrigation followed by foliar application of (50 μm ) MeJA. Drought stress substantially suppressed the yield and yield‐related traits, whereas it accelerated the membrane lipid peroxidation. Nonetheless, substantial increase in activities of enzymatic antioxidants (superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT)), proline, relative water contents (RWC) with simultaneous decrease in membrane lipid peroxidation was observed in MeJA‐treated plants under drought. These beneficial effects led to improvement in biological and grain yield, and harvest index under drought. Interestingly, MeJA application was also useful under well‐watered conditions. These results suggest the involvement of MeJA in improving the drought tolerance of soybean by modulating the membrane lipid peroxidation and antioxidant activities.     

Nitrogen Sustains Seed Yield of Quinoa Under Intermediate Drought

Quinoa (Chenopodium quinoa Willd.) is a promising crop for food security in dry areas. Studies have been conducted to define nitrogen (N) fertilization levels and to understand the responses of quinoa to drought, but little is known about the response of this crop to N fertilization under drought stress. The aim of this study was to investigate whether N fertilization could improve quinoa yield and physiology under limited water. A greenhouse experiment was carried out with quinoa grown at four N fertilization levels (0, 0.2, 0.4 and 0.6 g N pot^?1) and two watering treatments (progressive drought and full irrigation; 10 and 98 % of pot water holding capacity, respectively). Results of this experiment showed that N may confer a certain degree of drought tolerance to quinoa as seed quality and yield of N‐fertilized plants were not affected by drought stress. Responses such as faster stomatal closure, reduced leaf water potential, higher leaf abscisic acid (ABA) concentration and particularly an improved N remobilization in N‐fertilized plants may have played a role in sustaining seed yield in the drought‐stressed treatment. These results under controlled conditions serve as a basis to elucidate drought tolerance mechanisms activated with N fertilization and to define the use of N in management practices under semi‐arid environments.     

The Effect of Late-terminal Drought Stress on Yield Components of Four Barley Cultivars

Barley (Hordeum vulgare L.) is an important winter cereal crop grown in the semiarid Mediterranean, where late‐terminal drought stress during grain filling has recently become more common. The objectives of this study were to investigate the growth performance and grain yield of four barley cultivars under late‐terminal drought stress under both glasshouse and field conditions. At grain filling, four barley cultivars (Rum, ACSAD176, Athroh and Yarmouk) were exposed to three watering treatments: (1) well‐watered [soil maintained at 75 % field capacity (FC)], (2) mild drought stress at 50 % FC, (3) severe drought stress at 25 % FC in the glasshouse experiment and (1) well‐watered (irrigated once a week), (2) mild drought (irrigated once every 2 weeks), (3) severe drought (non‐irrigated; rainfed) in the field. As drought stress severity increased, gross photosynthetic rate, water potential, plant height, grain filling duration, spike number per plant, grain number per spike, 1000‐grain weight, straw yield, grain yield and harvest index decreased. In the glasshouse experiment, the six‐row barley cultivars (Rum, ACSAD176, and Athroh) had higher grain yield than the two‐row barley cultivar (Yarmouk), but the difference was not significant among the six‐row cultivars under all treatments. In the field experiment, Rum had the highest grain yield among all cultivars under the mild drought stress treatment. The two‐row cultivar (Yarmouk) had the lowest grain yield. In general, the traditional cultivar Rum had either similar or higher grain yield than the other three cultivars under all treatments. However, the yield response to drought differed between the cultivars. Those, Rum and ACSAD176, that were capable of maintaining a higher proportion of their spikes and grains per spike during drought also maintained a higher proportion of their yield compared with those in well‐watered treatment. In conclusion, cultivar differences in grain yield were related to spike number per plant and grain number per spike, but not days to heading or grain filling duration.     

Drought Priming at Vegetative Growth Stage Enhances Nitrogen‐Use Efficiency Under Post‐Anthesis Drought and Heat Stress in Wheat

To study the effects of early drought priming at 5th‐leaf stage on grain yield and nitrogen‐use efficiency in wheat (Triticum aestivum L.) under post‐anthesis drought and heat stress, wheat plants were first exposed to moderate drought stress (drought priming; that is, the leaf water potential reached ca. ?0.9 MP a) at the 5th‐leaf stage for 11 days, and leaf water relations and gas exchange rates, grain yield and yield components, and agronomic nitrogen‐use efficiency (ANUE ) of the primed and non‐primed plants under post‐anthesis drought and heat stress were investigated. Compared with the non‐primed plants, the drought‐primed plants possessed higher leaf water potential and chlorophyll content, and consequently a higher photosynthetic rate during post‐anthesis drought and heat stress. Drought priming also resulted in higher grain yield and ANUE in wheat under post‐anthesis drought and heat stress. Drought priming at vegetative stage improves carbon assimilation and ANUE under post‐anthesis drought and heat stress and their combination in wheat, which might be used as a field management tool to enhance stress tolerance of wheat crops to multiple abiotic stresses in a future drier and warmer climate.     

Improving the Productivity of Bread Wheat by Good Management Practices under Terminal Drought

Drought‐induced damages in crop plants are ranked at top amid all losses instigated by diverse abiotic stresses. Terminal drought (drought at reproductive phase) has emerged as a severe threat to the productivity of wheat crop. Different seed enhancement techniques, genotypes and distribution of crop plants in different spacings have been explored individually to mitigate these losses; however, their interaction has rarely been tested in improving drought resistance in wheat. This study was conducted to evaluate the potential role of different seed enhancement techniques and row spacings in mitigating the adversities of terminal drought in two wheat cultivars during two consecutive growing seasons of 2010–2011 and 2011–2012. Seeds of wheat cultivars Lasani‐2008 (medium statured) and Triple Dwarf‐1 (dwarf height) soaked in water (hydropriming) or CaCl₂ (osmopriming) were sown in 20‐, 25‐ and 30‐cm spaced rows; just before heading, the soil moisture was maintained at 100 % field capacity (well watered) or 50 % field capacity (terminal drought) till maturity. Terminal drought significantly reduced the yield and related traits compared with well‐watered crop; however, osmopriming improved the crop performance under terminal drought. Among different row spacings, wheat sown in 20‐cm spaced rows performed better during both years of study. Wheat cultivar Lasani‐2008 performed better than cultivar Triple Dwarf‐1 under both well‐watered and stress conditions. Maximum net returns and benefit–cost ratio were recorded from osmoprimed seeds of cultivar Lasani‐2008 sown in 20‐cm spaced rows under well‐watered condition. Nonetheless, osmoprimed seeds of cultivar Lasani‐2008 sown in 20‐cm spaced rows were better able to produce good yield under terminal drought.     

Water Use Efficiency, Carbon Isotope Discrimination and Biomass Production of Two Sugar Beet Varieties Under Well-Watered and Dry Conditions

Two sugar beet (Beta vulgaris sp.) varieties, which were supposed to differ in drought tolerance, were exposed to drought stress in a growth chamber and a container experiment in field. The aim was to test for (i) differences between the varieties in water use efficiency (WUE), biomass production and distribution and (ii) the relationship between WUE and carbon isotope discrimination (Δ), and between biomass production and Δ. Significant differences in WUE were detected between plants of well‐watered and drought treatments in both experiments, but not between the varieties. Production losses due to drought were large for both varieties in both experiments. Losses in the growth chamber were up to 50 % of plant dry weight and the corresponding value in the field was 24 %, when plants were given 60 and 30 %, respectively, of the full‐watered treatments. Significant negative correlations between WUE and Δ were found, but not between biomass production and Δ, when both varieties were included. Negative correlations between WUE and Δ were also found for each variety separately. The results suggest that Δ estimates from leaf tissue of sugar beet may provide a useful tool for genetic selection of drought‐tolerant sugar beet varieties.     

Genotype selection for physiological responses of drought tolerance using molecular markers in polycross hybrids of orchardgrass

The present study aimed to assess the effect of contrasting levels of molecular and phenotypic diversity among polycross parents of orchardgrass on the performance of synthetic progeny with respect to physiological responses and drought tolerance. Four polycross groups each composed of six parental plants were evaluated under normal irrigation and drought stress conditions. A number of 923 inter simple sequence repeats and sequence related amplified polymorphism markers and several phenotypic traits were used to select contrasting levels of diversity (high and low) in parental genotypes. Highly significant correlation was observed between molecular distance and progeny performances at both normal irrigation and drought stress conditions. High molecular diversity among polycross parents led to a significant yield advantage of first generation progeny with averages of 34.40% for normal irrigation and 48.10% for drought stress conditions. Also crosses between genetically distant parents produced progeny with considerable drought tolerance and yield stability. Positive associations between phenotypic distance of parents and progeny performance were found for most physiological traits at both moisture regimes but phenotypic distances had weak association with forage yield, stress tolerance index and yield stability of progeny. Significant associations between drought tolerance index and some physiological traits confirmed the importance of these traits in conferring drought tolerance of orchardgrass. Our results underscore the effectiveness of marker‐assisted polycross breeding to improve drought tolerance and yield stability through physiological traits in orchardgrass.     

利用抗旱选择导入系定位向日葵产量性状QTL

干旱是造成向日葵减产的最主要因素之一。利用综合性状优良的自交系K55作为轮回亲本与抗旱自交系K58杂交构建回交导入系, 在干旱条件下进行单株产量筛选, 得到45个BC₃F₂抗旱定向选择导入系。通过全基因组SSR及SNP标记扫描, 以方差分析和基于遗传搭车原理的卡方检验对呼和浩特市及武川县两点、两种水分条件下的5个产量性状进行QTL检测。方差分析检测到的QTL根据不同环境下的表达情况分为三类, 第一类在两种水分条件下稳定表达, 包括武川的4个百粒重QTL及呼和浩特的2个单株产量QTL、3个单株实粒数QTL, 这些QTL可能对向日葵抗旱性有直接贡献; 第二类受干旱胁迫表达, 包括呼和浩特的30个和武川的27个; 第三类仅在正常供水条件下被检测到, 包括呼和浩特的38个和武川的64个。卡方检验检测到极显著位点274个。用两种方法共检测到一致性位点14个, 可能是与向日葵抗旱性相关的关键位点。本研究结果可为向日葵高效抗旱分子育种奠定基础并提供相关材料。     

Fulvic Acid Application Improves the Maize Performance under Well‐watered and Drought Conditions

Water deficit is perhaps the most severe threat to sustainable crop production in the conditions of changing climate. Researchers are striving hard to develop resistance against water deficit in crop plants to ensure food security for the coming generations. This study was conducted to establish the role of fulvic acid (FA) application in improving the performance of hybrid maize (Zea mays L.) under drought. Maize plants were grown under normal conditions till tasselling and were then subjected to drought by cessation of water followed by foliar application of FA (1.5 mg l^?1). Drought stress disrupted the photosynthetic pigments and reduced the gas exchange leading to reduction in plant growth and productivity. Nonetheless, exogenous FA application substantially ameliorated the adversities of drought by sustaining the chlorophyll contents and gas exchange possibly by enhanced levels of antioxidant enzyme (superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT)) activities and proline. These beneficial effects yielded in terms of plant growth and allometry, and grain yield. It is interesting to note that FA application also improved the crop performance under well‐watered conditions. Hence, FA may be applied to improve the crop performance under drought and well‐watered conditions.     

Improving the Drought Tolerance in Rice (Oryza sativa L.) by Exogenous Application of Salicylic Acid

Drought stress encumbers the rice growth predominantly by oxidative damage to biological membranes and disturbed tissue water status. In this study, the role of salicylic acid (SA) to induce drought tolerance in aromatic fine grain rice cultivar Basmati 2000 was evaluated. SA was applied as seed and foliar treatments. For seed treatment, rice seeds were soaked in 50, 100 and 150 mg l⁻¹ aerated solution of SA for 48 h and then dried back. Treated and untreated seeds were sown in plastic pots in a phytotron. At four leaf stage, one set of plants was subjected to drought stress, while the other remained well watered. Drought was maintained at 50 % of field capacity by watering every alternate day. For exogenous application, SA was applied 50, 100 and 150 mg l⁻¹ at five leaf stage. In the control, SA was neither applied exogenously nor as seed treatment. Drought stress severely affected the seedling fresh and dry weight, photosynthesis, stomatal conductance, plant water relations and starch metabolism; however, SA application improved the performance of rice under both normal and stress conditions. Drought tolerance in rice was well associated with the accumulation of compatible solutes, maintenance of tissue water potential and enhanced potency of antioxidant system, which improved the integrity of cellular membranes and facilitated the rice plant to sustain photosynthesis and general metabolism. Foliar treatments were more effective than the seed treatments. Foliar application with 100 mg l⁻¹ (FA 100) was the best treatment to induce the drought tolerance and improve the performance under normal and stress conditions compared with the control or other treatments used in this study.     

Assessment of Groundnut under Combined Heat and Drought Stress

In semi‐arid regions, particularly in the Sahel, water and high‐temperature stress are serious constraints for groundnut production. Understanding of combined effects of heat and drought on physiological traits, yield and its attributes is of special significance for improving groundnut productivity. Two hundred and sixty‐eight groundnut genotypes were evaluated in four trials under both intermittent drought and fully irrigated conditions, two of the trial being exposed to moderate temperature, while the two other trials were exposed to high temperature. The objectives were to analyse the component of the genetic variance and their interactions with water treatment, year and environment (temperature) for agronomic characteristics, to select genotypes with high pod yield under hot‐ and moderate‐temperature conditions, or both, and to identify traits conferring heat and/or drought tolerance. Strong effects of water treatment (Trt), genotype (G) and genotype‐by‐treatment (GxTrt) interaction were observed for pod yield (Py), haulm yield (Hy) and harvest index (HI). The pod yield decrease caused by drought stress was 72 % at high temperature and 55 % at moderate temperature. Pod yield under well‐watered (WW) conditions did not decrease under high‐temperature conditions. Haulm yield decrease caused by water stress (WS) was 34 % at high temperature and 42 % under moderate temperature. Haulm yield tended to increase under high temperature, especially in one season. A significant year effect and genotype‐by‐environment interaction (GxE) effect were also observed for the three traits under WW and WS treatments. The GGE biplots confirmed these large interactions and indicated that high yielding genotypes under moderate temperature were different to those at high temperature. However, several genotypes with relatively high yield across years and temperature environments could be identified under both WW and WS conditions. Correlation analysis between pod weight and traits measured during plant growth showed that the partition rate, that is, the proportion of dry matter partitioned into pods, was contributing in heat and drought tolerance and could be a reliable selection criterion for groundnut breeding programme. Groundnut sensitivity to high‐temperature stress was in part related to the sensitivity of reproduction.     

Drought‐induced osmotic adjustment and changes in carbohydrate distribution in leaves and flowers of cotton (Gossypium hirsutum L.)

Research has indicated osmotic adjustment as a mechanism by which leaves and roots of cotton plants overcome a drought period. However, the relevance of this mechanism in reproductive tissues of modern cultivars under drought has not been fully investigated. The objectives of this study were to measure osmoregulation and carbohydrate balance in reproductive tissues and their subtending leaves grown under water‐deficit conditions. Two cotton cultivars were grown under controlled environment and field conditions. Plants were exposed to water‐deficit stress at peak flowering, approximately 70 days after planting. Measurements included stomatal conductance, proline concentration, soluble carbohydrates and starch concentration, and water potential components. Stomatal conductance of drought‐stressed plants was significantly lower compared to control, while osmotic adjustment occurred in reproductive tissues and their subtending leaves by different primary mechanisms. Pistils accumulated higher sucrose levels, maintaining cell turgor in plants exposed to drought at similar levels to those in well‐watered plants. However, subtending leaves lowered osmotic potential and maintained cell turgor by accumulating more proline. Soluble carbohydrates and starch concentration in leaves were more affected by drought than those of floral tissues, with corresponding reduction in dry matter, suggesting that flowers are more buffered from water‐deficit conditions than the adjacent leaves.     

Influence of Soil Water Regimes on VA Mycorrhiza IV. Effect on Root Growth and Water Relations of Sorghum bicolor

In a greenhouse trial, non-mycorrhizal and mycorrhizal plants of Sorghum bicolor were grown at three water regimes. The root length and root morphology of Sorghum bicolor was monitored in two soils during 34 days. From 29 days on, total root length of mycorrhizal sorghum was greater than of non-mycorrhizal sorghum in moderate and high water stress conditions. In soil A, at all water regimes a lower percentage of coarse roots and smaller root length per leaf area were found with mycorrhizal plants; in soil B, this was only the case in well watered conditions. In general, all root and water relation parameters were less affected by water stress when plants were mycorrhizal; this less sensitivity of mycorrhizal sorghum may increase the tolerance of the plant to drought. However, water relations of plants were indirectly enhanced by mycorrhiza via increased P uptake.     

Evaluating the role of seed priming in improving drought tolerance of pigmented and non‐pigmented rice

This study was conducted to evaluate the influence of seed priming on drought tolerance of pigmented and non‐pigmented rice. Seeds of pigmented (cv. Heug Jinju Byeo) and non‐pigmented (cv. Anjoong) rice were soaked in water (hydropriming) or solution of CaCl₂ (osmopriming). Seeds were sown in soil‐filled pots retained at 70 (well‐watered) and 35% (drought) water‐holding capacity. Drought stress caused erratic and poor stand establishment and decreased the growth of both rice types. More decrease in plant height and leaf area under drought stress was noted in pigmented rice, whereas decrease in root length and seedling dry weight, under drought, was more obvious in non‐pigmented rice. Pigmented rice maintained more tissue water and photosynthesis and had more polyphenols, flavonoids and antioxidant activity than non‐pigmented rice. Seed priming was effective in improving stand establishment, growth, polyphenols, flavonoids and antioxidant activity; however, extent of improvement was more in pigmented rice under drought. In conclusion, drought caused erratic germination and suppressed plant growth in both rice types. However, pigmented rice had better drought tolerance owing to uniform emergence, and better physiological and morphological plasticity. Seed priming was quite helpful in improving the performance of both rice types under drought and well‐watered conditions.     

过表达OsMPK17激酶蛋白质增强了水稻的耐旱性

促分裂原活化蛋白质激酶(mitogen-activated protein kinase, MAPK)在真核生物中高度保守,在水稻逆境应答反应中也发挥着重要作用。本研究表达纯化了水稻OsMPK17蛋白质,制备了特异性抗体,对多种非生物逆境胁迫下的蛋白质样品进行免疫印迹分析,发现OsMPK17蛋白质在干旱胁迫下诱导表达,提示该蛋白质在干旱胁迫应答中发挥作用。对脱落酸和茉莉酸甲酯处理的离体叶片蛋白质分析发现,OsMPK17蛋白质表达丰度下降,提示该蛋白质的功能发挥可能受激素调控。为此,构建了过表达OsMPK17蛋白质的载体,转化水稻后筛选获得了OsMPK17蛋白质过表达的纯合株系。田间种植鉴定结果表明,转基因株系的株高变矮、穗长变短、结实率降低。种子萌发期拟旱(PEG-6000)处理条件下,过表达OsMPK17株系的种子长势明显比野生型好,根长与芽长均显著大于野生型。幼苗期失水试验表明,转基因植株的失水率低于野生型。在土培干旱胁迫后恢复浇水的试验中,过表达OsMPK17蛋白质的转基因水稻生长也好于野生型。综上,过表达OsMPK17蛋白质提高了水稻的耐旱性。本研究增进了对水稻OsMPK17基因功能的了解。     

Root distribution patterns of peanut genotypes with different drought resistance levels under early‐season drought stress

Drought severely limits crop yield of peanut. Yet cultivars with enhanced root development enable the exploration of a greater volume of soil for water and nutrients, helping the plant survive. Root distribution patterns of three genotypes (ICGV 98305, ICGV 98324 and Tifton‐8) were compared when grown in well‐watered rhizoboxes and when grown in rhizoboxes where an early‐season drought was imposed using rain‐exclusion shelters. The treatments were arranged in a completely randomized design with three replications, and the experiment was conducted during two seasons at the Field Crop Research Station of Khon Kaen University, in Khon Kaen, Thailand. The root system of ICGV 98305, when grown under drought, had a significantly higher root length in the 30–110 cm deep soil layers and less roots in the 0–30 cm soil layers when under drought than when grown under well‐watered conditions. Roots of Tifton‐8 had the largest reductions in root length in upper soil layer and reduced in most soil layers. Tifton‐8 grown under drought was smaller than under well‐watered control for all root traits, showing negative response to drought. The peanut genotypes with high root traits in deeper soil layer under early‐season drought might contribute to drought avoidance mechanism.     

Old and New Cultivars of Soya Bean (Glycine max L.) Subjected to Soil Drying Differ in Abscisic Acid Accumulation,Water Relations Characteristics and Yield

Two old (Huangsedadou and Longxixiaohuangpi (LX)) and two new (Jindou 19 (JD) and Zhonghuang 30 (ZH)) soya bean (Glycine max (L.) Merr.) cultivars were used to investigate the influence of soil drying on the abscisic acid (ABA) accumulation in leaves, stomatal conductance (g_s), leaf water relations, osmotic adjustment (OA), leaf desiccation tolerance, yield and yield components. The greater ABA accumulation was induced by soil drying, which also inducing g_s decreased at higher soil water contents (SWC) and leaf relative water content (RWC) significantly decreased at lower SWC in the new soya bean cultivars than in the old soya bean cultivars. The soil water threshold between the value at which stomata began to close and the RWC began to decrease was significantly broader in the new cultivars than in the old cultivars. The new cultivars had significantly higher OA and lower lethal leaf water potential than old cultivars when the soil dried. The old cultivars had greater biomass, but lower grain yield than the new cultivars in well‐watered, moderate stress and severe stress conditions. Thus with soil drying, the new soya bean cultivars demonstrated greater adaptation to drought by inducing greater ABA accumulation, stomatal closure at higher SWC, enhanced OA and better water relations, associated with increased leaf desiccation tolerance, greater water use efficiency and higher yield.     

Transformation of tobacco with an Arabidopsis thaliana gene involved in trehalose biosynthesis increases tolerance to several abiotic stresses

Summary Trehalose (a non-reducing disaccharide) plays an important role in abiotic stress protection. It has been shown that using trehalose synthesis genes of bacterial origin, drought and salt tolerance could be achieved in several plants. A cassette harboring the AtTPS1 gene under the control of the CaMV35S promoter and the Bialaphos resistance gene was inserted in the binary plasmid vector pGreen0229 and used for Agrobacterium-mediated transformation of tobacco (Nicotiana tabacum). T0 plants obtained were analyzed by PCR for the presence of AtTPS1 gene. Thirty lines were positive and seeds were germinated on media with 6 mg/l PPT to obtain T1 plants that were grown in the greenhouse to obtain T2 seeds that were germinated on selective media. Lines which seeds showed a 100 % survival rate were considered homozygous transgenic T1 lines. Three lines were selected and gene expression confirmed by northern and western blots. Transgenic seeds were germinated on media with different concentrations of mannitol (0, 0.25, 0.5 and 0.75 M) and sodium chloride (0, 0.07, 0.14, 0.2, 0.27 and 0.34 M) to score their tolerance to osmotic stress. Assays were conducted to test the tolerance of transgenic plants to drought (measurement of water percentage as a consequence of water withdrawal), desiccation (measurement of water loss as a consequence leaf detaching) and temperature stresses (germination at 15 ^∘C and 35^∘C). Transgenic tobacco plant lines registered higher germination rates under osmotic and temperature stress situations than did wild-type plants. Responses to drought and desiccation stresses were similar for all plant lines. It can hence be suggested that the heterologous expression of TPS1 gene from Arabidopsis can be used successfully to increase abiotic stress tolerance in model plants and probably in other crops.     

Relationships between leaf morpho‐anatomy,water status and cell membrane stability in leaves of wheat seedlings subjected to severe soil drought

The impact of the genotype‐specific leaf morphological and anatomical characteristics on the ability of wheat plants to preserve leaf water balance and cell membranes stability under drought stress was investigated. Seedlings of six modern semi‐dwarf (carriers of Rht, Reduced height genes) and six old tall bread wheat varieties were subjected to soil drought by withholding watering for 6 days. Morpho‐anatomical traits (leaf area, perimeter, thickness, stomata and trichome density) of daily watered (control) plants were characterized by light microscopy, scanning and image analyses. The leaf water status in both control and stressed plants was determined by measuring the relative water content (RWC). The leaf cell membranes stability in stressed plants was estimated by conductometric determination of the membranes injury index. On average, the modern semi‐dwarf varieties had less leaf area and leaf perimeter, and less dissection index, a parameter characterizing the leaf shape. Under drought stress, the modern genotypes maintained better water balance evidenced by significantly higher leaf RWC and better‐preserved the cell membranes stability supported by significantly lower Injury index. The correlations between morpho‐anatomical traits in control plants and drought tolerance‐related traits showed that the higher the leaf dissection index (i.e. more oblong leaves), the greater the water loss and the leaf membrane damages after desiccation were. The effect of shape of the evaporating surface on the water loss was modelled using wet filter paper. Similar to plant leaves, the evaporation and, respectively, water loss from paper pieces of more oblong shape (i.e. higher dissection index) was more intensive. The elucidation of the impact of the leaf shape on transpiration might contribute to better understanding of the mechanisms used by plants to maintain water reserves during drought stress and could be a basis for developing of simple and fast screening methods aiding the selection of drought tolerant genotypes.