Effect of Water Stress on Physiological Attributes and their Relationship with Growth and Yield of Wheat Cultivars at Different Stages

The effects of water stress on physiological attributes of drought‐sensitive (Kalyansona) and drought‐tolerant (C‐306) wheat cultivars were studied in a pot experiment. Water stress was imposed by withholding irrigation at boot and anthesis stages. Leaf water potential, leaf osmotic potential and leaf turgor potential (measured with pressure chamber and osmometer), as well as leaf diffusive resistance, leaf transpiration rate and leaf‐to‐air transpiration gradient (measured with a steady‐state porometer) were measured diurnally. Growth and yield parameters were recorded after harvesting of the crop. Triplicate data were analysed using a completely randomized design and correlations amongst these parameters were computed. Water stress was found to reduce diurnal leaf water potential and leaf osmotic potential in both the genotypes but leaf osmotic potential was significantly higher in the drought‐tolerant cultivar C‐306 than in the drought‐sensitive cultivar Kalyansona. Positive turgor was recorded in both the genotypes under water stress and non‐stress conditions. Water‐stressed plants showed significantly lower turgor potential than control plants. In diurnal observations, water‐stressed plants exhibited significantly higher leaf diffusive resistance in both genotypes at both stages. The diffusive resistance of C‐306 was predominantly higher than that of Kalyansona. Water stress decreased leaf transpiration rate at both stages but the reduction was higher at the anthesis stage. The leaf‐to‐air temperature gradient was much higher in C‐306 than in Kalyansona at the boot stage but at the anthesis stage genotypic variation was non‐significant. The capacity to maintain cooler foliage was lower at the anthesis stage than at the boot stage in both the cultivars. Shoot dry weight, number of grains, test weight, grain yield, biological yield and harvest index decreased to a greater extent when water stress was imposed at the anthesis stage, while imposition of water stress at the boot stage caused a greater reduction in plant height and number of tillers. Similarly, water stress caused a smaller reduction in growth, yield and yield attributes in C‐306 than in Kalyansona. In general, the correlation coefficient of grain and biological yield with water potential and its components was positive and highly significant. Similarly, turgor potential was also correlated positively and significantly with grain yield at both the stages, but with biological yield it was significant only at the anthesis stage. A negative and significant correlation was obtained for diffusive resistance and leaf‐to‐air temperature gradient with grain yield at the boot and anthesis stages. The rate of transpiration was also positively and significantly correlated to grain and biological yields at both the stages. Amongst the yield attributes, number of leaves and number of tillers were positively correlated at the anthesis stage, whereas leaf area and shoot dry weight were significantly correlated with grain and biological yields at both the stages.     

水分胁迫条件下高粱叶片的渗透调节及其对气孔导度和蒸腾速率的影响

两个抗旱性不同的高粱品种“3197B”和“三尺三”,在水分胁迫条件下,抗旱品种3197B渗透势降低,渗透调节能力较强.正常灌水时,两品种的气孔导度和蒸腾速率均随光照增强而增加,品种间差异不大;水分胁迫条件下,上午3197B气孔导度和蒸腾速率高于三尺三,午后水分胁迫严重时又低于三尺三,但其叶水势和膨压比三尺三高.     

土壤干旱对小麦叶片渗透调节和光合作用的影响

本文研究了土壤干旱对小麦叶片渗透调节和光合作用的影响.小麦叶片水势、相对含水量、饱和渗透势、光合速率、蒸腾速率和气孔导度随土壤干旱程度加剧呈现出先缓降后陡降的趋势,其变化的土壤相对含水量阈值相同.小麦旗叶的渗透调节能力约为0.5MPa,不同叶位叶片渗透调节能力不同,其强弱顺序为旗叶>倒二叶>倒三叶.干旱使叶片膨压丧失时的渗透势从正常水分处理的-1.61MPa降到-2.33MPa,弹性模量从5.74MPa增加到6.35MPa.干旱条件下的光合速率、气孔导度、气孔限制值和叶片光合放氧能力都下降,而细胞间隙CO_2含量增加,说明光合速率的降低是非气孔因素即叶肉细胞光合活性限制的结果.     

The Influence of Plant Water Stress on Net Photosynthesis and Leaf Area of Two Maize (Zea mays L.) Cultivars

The effect of plant water stress on net photosynthesis and leaf growth were investigated in order to determine to what extent leaf water potential during vegetative growth and silking affects maize development.
Two commercial maize hybrids grown in pots in a glasshouse were subjected to leaf water potentials of -1300 and -1700 kPa during the eighth leaf stage and during silking to -1700 and -2300 kPa to previously unstressed, moderately and severely stressed plants. The effect of stress on inhibiting CO₂ uptake rates and leaf areas, as well as the recovery after alleviating stress, were compared to that of unstressed plants.
No substantial differences in CO₂ uptake rates were found between medium and long seasoned cultivars. The CO₂ uptake rates per unit leaf area decreased to negative values under both moderate and severe stress conditions during both growth stages. During silking, the recovery of CO₂ uptake rate was much lower than during the eight leaf stage. Leaf area decreased proportionally with increased stress but did not recover after alleviating stress on plants stressed during both the eighth leaf and silking stages.     

石新733小麦的水分生理特点及节水灌溉效应

石新733是一个高产优质小麦新品种,为探明其是否适用于节水高产栽培,于2003—2004和2004—2005年度进行了节水灌溉对其水分生理性状和产量影响的田间试验。结果表明,石新733的叶片渗透调节能力比邯麦9、石麦9和衡7228的平均值高71.6%,叶水势比衡7228约高0.1 MPa。石新733的离体叶片失水速率较高;蒸腾速率、净光合速率和气孔导度与石麦9和邯麦9接近,均高于衡7228;胞间CO₂浓度和蒸腾效率品种间没有明显差别。与灌5水处理相比,灌2水处理的叶水势和叶片气体交换参数均相近而灌浆盛期的光合功能和蒸腾效率较高。石新733的产量高于其他3个品种,其中,不灌水和灌2水处理分别比其他3个品种平均产量增加11.3%和7.0%。全生育期只灌拔节和抽穗开花期2水的节水处理比灌4水的常规灌溉处理增产5.6%,说明该品种可在节水高产栽培上应用。     

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.     

Effects of Increasing Salinity Stress and Decreasing Water Availability on Ecophysiological Traits of Quinoa (Chenopodium quinoa Willd.) Grown in a Mediterranean‐Type Agroecosystem

Quinoa is a native Andean crop for domestic consumption and market sale, widely investigated due to its nutritional composition and gluten‐free seeds. Leaf water potential (Ψ_leaf) and its components and stomatal conductance (g_s) of quinoa, cultivar Titicaca, were investigated in Southern Italy, in field trials (2009 and 2010). This alternative crop was subjected to irrigation treatments, with the restitution of 100 %, 50 % and 25 % of the water necessary to replenish field capacity, with well water (100 W, 50 W, 25 W) and saline water (100 WS, 50 WS, 25 WS) with an electrical conductivity (EC_w) of 22 dS m^?1. As water and salt stress developed and Ψ_leaf decreased, the leaf osmotic potential (Ψ_π) declined (below ?2.05 MPa) to maintain turgor. Stomatal conductance decreased with the reduction in Ψ_leaf (with a steep drop at Ψ_leaf between ?0.8 and 1.2 MPa) and Ψ_π (with a steep drop at Ψ_π between ?1.2 and ?1.4 MPa). Salt and drought stress, in both years, did not affect markedly the relationship between water potential components, RWC and g_s. Leaf water potentials and g_s were inversely related to water limitation and soil salinity experimentally imposed, showing exponential (Ψ_leaf and turgor pressure, Ψ_p, vs. g_s) or linear (Ψ_leaf and Ψ_p vs. SWC) functions. At the end of the experiment, salt‐irrigated plants showed a severe drop in Ψ_leaf (below ?2 MPa), resulting in stomatal closure through interactive effects of soil water availability and salt excess to control the loss of turgor in leaves. The effects of salinity and drought resulted in strict dependencies between RWC and water potential components, showing that regulating cellular water deficit and volume is a powerful mechanism for conserving cellular hydration under stress, resulting in osmotic adjustment at turgor loss. The extent of osmotic adjustment associated with drought was not reflected in Ψ_π at full turgor. As soil was drying, the association between Ψ_leaf and SWC reflected the ability of quinoa to explore soil volume to continue extracting available water from the soil. However, leaf ABA content did not vary under concomitant salinity and drought stress conditions in 2009, while differing between 100 W and 100 WS in 2010. Quinoa showed good resistance to water and salt stress through stomatal responses and osmotic adjustments that played a role in the maintenance of a leaf turgor favourable to plant growth and preserved crop yield in cropping systems similar to those of Southern Italy.     

高产冬小麦叶水势的变化特点与节水调控

１９８６－１９９０四个年度研究结果显示，叶水势是变化困供水及生育时期而不同。黎明前叶水势随生育进程而变化，开花期出现明显低谷，与土壤水分动态变化不一致；午后叶水势具有规律的阶段性变化，且因不同水文年型出现间差异。叶水势与土壤含水量呈曲线关系，随生育进程，叶水势与深层土壤水分的相关性增强。开花期叶水势与产量关系最为密切。前控式节水栽培可通过渗透调节维持较高膨压而高产。提出了不同水文年型高产节水主要生     

土壤水分胁迫下小麦叶片的渗透调节与膨压维持

两年的试验结果表明,在土壤缓慢脱水和长期水分胁迫下,四个小麦品种叶片均产生渗透调节,孕穗期和灌浆期渗透调节能力较强,渗透调节的幅度为0.40～0.64MPa,抗旱性强的品种大于抗旱性弱的品种.由于渗透调节在土壤含水量60%左右或轻度胁迫下,叶片膨压基本不变.五个生育期四个处理水平叶水势与膨压回归分析,从水势每下降一个单位,膨压降低的单位数看,昌乐5号(0.146)<山农587(0.151)<烟农15(0.162)<济南13(0.240),抗旱性强的品种由于渗透调节能力强,膨压降低的单位数小,维持膨压的程度高.     

Remobilization of Proline and Other Nitrogen Compounds from Senescing Leaves of Maize under Water Stress

The effects of water stress around anthesis on proline accumulation and translocation from leaves of two maize cultivars (DA 4F37 and DA XL636) were studied. Water stress increased leaf proline content only in DA 4F37, while proline in leaf exudates was detected only in DA XL636 water-stressed plants. Proline translocation was not associated with increased nitrogen remobilization from leaves. The accumulating proline cultivar DA 4F37 showed a higher osmotic adjustment capacity than DA XL636. Leaf proline content in water-stressed DA 4F37 plants varied with daytime. High proline concentration during the morning was found in leaves with high relative water content. This evidence would support the hypothesis that proline is involved in osmotic adjustment.     

Relationships between Grain Yield, Flag Leaf Morphology, Carbon Isotope Discrimination and Ash Content in Irrigated Wheat

The purpose of this study was to examine how differences in leaf angle, leaf rolling (LR) and glaucousness (GL) can modify yield components and leaf physiological traits in wheat. A set of 167 lines derived from a cross between two high‐yielding bread wheat cultivars differing for these traits was grown under flood irrigation and high evaporative demand in the north‐west of Mexico. Area, mass per unit area and chlorophyll content of the flag leaf were assessed. Carbon isotope discrimination (Δ) and ash content (m_a) were also measured. A significant correlation was found between grain yield (GY) and both Δ and m_a suggesting that, despite well‐watered conditions, leaf stomatal conductance was the main yield‐limiting factor. Leaf posture and LR did not significantly affect yield, Δ and m_a. Higher grain weight was noted, however, in lines with droopy flag leaves. Erect leaves had higher mass per unit area. GL was associated with a significant increase in GY and grain weight. Glaucous lines also had higher Δ and m_a, suggesting higher transpiration rate and lower transpiration efficiency. The study confirms that Δ and m_a represent promising criteria for GY in wheat and provides evidence that GL can contribute to higher yield, even under irrigated conditions.     

Sensitivity of Two Quinoa (ChenopodiumquinoaWilld.) Varieties to Progressive Drought Stress

Quinoa (ChenopodiumquinoaWilld.) is a highly nutritious Andean seed crop which shows great potential to grow under a range of hostile environments. The objective of this study was to investigate the differences of drought tolerance of a Bolivian (Achachino) and a Danish (Titicaca) variety, and especially drought‐related adaption strategies. Soil water status was expressed as the fraction of transpirable soil water (FTSW). Relative stomatal conductance (RSC), relative transpiration (RT) and relative leaf water potential (RLW) were calculated by determining stomatal conductance, transpiration rate and leaf water potential of the drought‐treated plants relative to those of fully irrigated plants. The responses of RSC, RT and RLW to decreasing FTSW were described by a linear‐plateau model. The critical value of FTSW was the threshold of FTSW where the parameters studied decreased. The thresholds increased C_S for stomatal conductance, C_T for transpiration and C_Lfor leaf water potential. Achachino showed significantly lower C_T and C_L when compared with Titicaca, implying that transpiration and leaf water potential were less affected under mild drought conditions in the Bolivian variety. C_S in Achachino was significantly higher than C_L and C_T, which indicated that stomatal conductance declined before transpiration and leaf water potential were reduced. Such difference was found in Titicaca where reduction of leaf area had more effect on transpiration than stomatal closure. Slower growth rate and smaller leaf area in combination with a lower stomatal conductance was found to contribute to drought resistance in Achachino. ABA concentration in the xylem sap tended to increase in both varieties after 2 days onset of drought, prior to decline in leaf water potential. Titicaca showed significantly (P < 0.05) higher ABA concentration when compared with Achachino under both fully irrigated and drought conditions. Titicaca had higher xylem nutrient concentration in comparison with Achachino in both fully‐watered and drought plants at day 2 after onset of soil drying. It was concluded that Titicaca was more sensitive to progressive drought than Achachino which avoided water loss by means of lower growth rate and smaller leaf area.     

Evaluation of Polyethylene Glycol Test for Measuring Cell Membrane Stability in Maize

Cell membrane stability (CMS) of ten maize ( Zea mays L.) cultivars was measured by the polyethylene glycol (PEG) test and compared with other nutritional and physiological measurements to examine the nutriophysiological meanings of the test. Osmotic potential of leaf tissues was well correlated with CMS measured as percentage injury in the PEG test and it was suggested that it may have influenced on desiccation treatment in the PEG test. Leaf water potential, stomatal resistance and cuticular resistance did not show any correlation with CMS measured. Cultivars with high leaf water content were high in CMS and were tolerant to desiccation stress in the PEG test. They showed high excised-leaf water retention capability. Sugar, K. and Ca were the major solutes which contributed to osmotic potential. Potassium concentration in leaf tissues was well correlated with CMS, while sugar was not. It was suggested that K may play another role in increasing CMS in maize apart from its role as an osmotic substance.     

高产冬小麦节水栽培的叶水势特征

田间和盆栽试验研究表明叶水势日变化曲线因供水和生育时期而不同，黎明前叶水势（ψ＾ｐｒｅ）开花期低谷十分明显，与土壤水分动态变化不一致，午后叶水势表现为前期低中期高后期渐降的变化特点，不同水文年型间存在差异，生育中后期叶水势与深层土壤水分含量的相关程度增强，开花期叶水势与产量关系最为密切。前期控水式的节水栽培在一定程度上降低生育期叶水势，可通过渗透调节功能和较高膨压的维持稳定高产。     

Relationships between Leaf Water Potential, Canopy Temperature and Transpiration in Irrigated and Nonirrigated Wheat

Research is needed to characterize the crop response to soil water deficit through plant parameters. Leaf water potential (LWP), canopy temperature (CT) and transpiration rate (TR) served as indicators of stress and were measured using a pressure chamber, infrared thermometer and porometer, respectively, in irrigated and nonirrigated wheat ( Triticum aestivum L.) grown on Haldi loam soil. Nonirrigated wheat had consistently higher CT and, lower LWP and TR during the day. As drought intensified, differences between irrigated and nonirrigated wheat became large and the maximum differences in CT, LWP and TR occurred at 14.00 h where they equalled 3.8 °C, 9 bar and 7.6 μg cm^−2: sec⁻¹, respectively, on 109 days after sowing (DAS). In nonirrigated wheat LWP declined at a faster rate until the peak stress period (14.00 h) approached and recovered slowly in the later afternoon and TR increased slowly in the forenoon and declined rapidly in the afternoon as compared with irrigated wheat. Canopy temperature (CT) of nonirrigated plants increased earlier during forenoon and remained higher later in the afternoon than CT of irrigated plants. At a same TR, lower values of LWP and higher values of CT were observed in the afternoon than in the forenoon due to which the phenomenon of hysteresis exhibited. The degree of hysteresis increased with increasing plant water deficit and crop age.     

Effect of Drought and Nitrogen Availability on Osmotic Adjustment of Five Pearl Millet Cultivars in the Vegetative Growth Stage

Growth of pearl millet (Pennisetum glaucum (L.) R. Br.) is affected in areas with limited and erratic rainfall, often combined with nitrogen deficiency. Therefore, effects of severe drought and nitrogen availability on mechanisms of dehydration avoidance were investigated. Five pearl millet genotypes were cultivated in soil differing in nitrogen availability, low (N1), medium (N2) or high (N3) in a climate chamber. Thirty‐five days after sowing, the plants were exposed to drought for 12 days. Drought decreased leaf area and stomatal conductance strongly and caused leaf rolling. In the youngest fully expanded leaves, drought led to an osmotic adjustment from around ?0.5 to ?0.9 MPa, in N1 and N2 substantially achieved by potassium accumulation. Nitrate contributed to the osmotic adjustment in N2 and N3, proline only slightly, increasingly from N1 to N2, whereas the sum of glucose, fructose and sucrose did not play a role. The dehydration independent osmotic force for water uptake (osmotic potential at full turgor) was under drought strongest at N2 and in the landrace Dembi Yellow stronger than in the cultivars Ashana and Ugandi. This contributed to the higher relative water content (RWC) of ‘Dembi Yellow’, whereas due to other factors nitrogen had no effect on the RWC.     

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.     

土壤水分胁迫对冬小麦叶片渗透调节及叶绿体超微结构的影响

土壤水分胁迫下 ,抗旱性强的小麦品种昌乐 5号、北农 2号与抗旱性弱的济南 13、鲁麦 5号相比 ,渗透调节能力高 0 4 1～ 0 60MPa ,相对含水量少降 6 39～ 10 74个百分点 ,叶水势少降 0 19～ 0 63MPa。水分胁迫使小麦叶片光合能力下降 ,水分胁迫全过程下降平均百分数 ,抗旱性强的品种比抗旱性弱的品种光合速率少降 17 7%～ 2 2 5% ;气孔导度少降 2 1 0 6%～2 3 75%。小麦叶肉细胞叶绿体的超微结构发生变化且随水分胁迫的加重而加剧 ,但变化程度与小麦的抗旱性及渗透调节能力成负相关。胁迫导致叶绿体外形变圆 ,类囊体肿胀 ,片层间距加大 ,基质片层模糊 ,最终叶绿体解体     

Influence of Solar Radiation and Vapour Pressure Deficit on Transpiration Efficiency of Rainfed Sorghum

Besides assimilation, plant water relations are important aspects of physiological basis of productivity of crops in water limited environment. The relationships of photosynthesis rate, transpiration rate, leaf water potential and stomatal conductance with photosynthetically active radiation (PAR) and vapour pressure deficit (VPD) during pre-flowering (panicle initiation to ear emergence) and grain filling (from anthesis to maturity) stages of a sorghum hybrid (cv. CSH-6 ) grown under rainfed conditions were studied. Photosynthesis rate declined when PAR was above 1300 μmol m⁻² s⁻¹. during both the growth stages. Higher transpiration rate during grain filling stage at higher PAR caused the transpiration efficiency to be lower than during pre-flowering stage when PAR was above 1200 μmol m⁻²s⁻¹.Leaf water potential and stomatal conductance decreased with increase in PAR. Leaf water potential was higher during pre-flowering than during grain filling stage but maximum photosynthesis rate was similar during both the growth stages. Changes in VPD did not qualitatively alter the relationships of the physiological variables with PAR.
Decreasing photosynthesis rate and LWP at high PAR suggest that photosynthesis rate was limited by low leaf water potential when PAR was optimal, and by low PAR even when leaf water potential was high in rainfed sorghum during rainy season.     

Water relations, gas exchange and growth of cool-season grain legumes in a Mediterranean-type environment

The aim of this study was to identify the physiological characteristics which may affect the yield of six cool-season grain legume species grown in a water-limited Mediterranean-type climate in Western Australia. The rate of net photosynthesis, stomatal conductance and water relations were measured from flowering to complete leaf senescence in white lupin, chickpea, faba bean, field pea, grass pea and lentil. In irrigated plants, the midday leaf water potential was about −0.6 MPa in all species, while the maximum rate of leaf photosynthesis was 30 μmol m⁻² s⁻¹ for chickpea and white lupin, and below 20 μmol m⁻² s⁻¹ for the other species. With the development of water deficits, the leaf water potential in rain-fed plants decreased to about −3 MPa in chickpea and lentil and −2 MPa in the other species. Photosynthesis and stomatal conductance decreased markedly as the leaf water potential decreased below −0.9 MPa in all six species, including chickpea and lentil, which showed a high degree of osmotic adjustment. Despite the similarity in water use, restricted to the top 40 cm of soil, and water relations characteristics, yields varied markedly among species. Yields were strongly correlated with early biomass production and early pod development.