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1.
Compensatory Growth Responses During Reproductive Phase of Cowpea after Relief of Water Stress 总被引：1，自引：0，他引：1
Unpredictable drought affects growth and yield of dryland cowpea ( Vigna unguiculata [L.] Walp.) during rainy season. With the objective of identifying compensatory growth responses after relief of water stress, pot-grown plants (cv. C-752) were water-stressed at flowering, and physiological responses, short term dry matter partitioning upon relief of water stress, and productivity at maturity were studied. Water stress decreased, to varying degrees, leaf water potential, stomatal conductance, photosynthesis rate and transpiration rate. Recovery in assimilation lagged behind that in water relations. Assimilate supply seemed to be limiting early pod growth upon relief of water stress due to low photosynthesis rate, reduced leaf area per pod, and increased partitioning to leaf expansion. However, later pod growth was not limited by assimilate supply and final dry matter per pod was similar in both non-stressed and stress-affected plant. Cowpea exhibited the following growth responses during pod-fill stage upon relief of water stress: 1. increase in leaf area, 2. shift in dry matter partitioning in favour of leaf expansion, 3. extended green leaf duration, and 4. increase in pod number. These partially compensating physiological responses probably ensure reasonable productivity of dryland cowpea during rainy season. 相似文献
2.
腐殖酸水溶肥料对水分胁迫下小麦光合特性及产量的影响 总被引：3，自引：1，他引：2
为了解腐殖酸水溶肥料对水分胁迫下小麦光合特性及产量的影响。以‘永良四号’为试验材料,采用盆栽方法研究了拔节期水分胁迫后,腐殖酸水溶肥料对小麦叶绿素含量、光合速率、气孔导度、蒸腾速率及产量的影响。结果表明,在不同水分胁迫下,腐殖酸水溶肥料均有效地改善了小麦光合特性,与对照相比,叶绿素含量增加5.62%~84.32%,光合速率增加0.87%~75.38%,气孔导度降低7.96%~53.25%,蒸腾速率降低15.96%~58.32%。水分胁迫后,净光合速率和叶绿素含量下降。但在水分胁迫时喷施腐殖酸水溶肥料,叶绿素含量和净光合速率增加,蒸腾速率减弱,因而水分利用效率提高。小麦增产4.48%~7.75%,增产效果显著,增产幅度为：正常供水>适度控水>中度水分胁迫。综合分析表明,腐殖酸水溶肥料能改善小麦光合特性,增加其产量。 相似文献
3.
Summary A comparative study of photosynthetic response to water stress was conducted with one genotype of wild einkorn (Triticum boeoticum, W) and one of domesticated einkorn (T. monococcum, C).Per unit leaf area, W showed a better performance for photosynthetic and transpiration activities, even under dry air and dry soil conditions. Its leaf water potential was always higher than that of C at any level of soil water potential. The difference in photosynthetic recovery from severe drought between W and C was also obvious. The photosynthetic rate, transpiration rate and water status of the leaves observed at 20 h after rewatering was almost the same as non-stressed leaves in W, whereas in C the photosynthetic rate was about half that of the non-stressed leaves, which was accompanied with a low transpiration rate and a high gas diffusion resistance. The ability of W to maintain a proper water balance over a wide range of soil water potential and to recover rapidly from severe drought seems to be a result of adaptation to its hard habitats.However, under favourable water supply, the photosynthetic rate per unit leaf nitrogen was higher in C than in W. This may be advantageous to bring about a better plant growth than W on the arable land where the improved water supply is guaranteed. 相似文献
4.
Y. Sun F. Liu M. Bendevis S. Shabala S.‐E. Jacobsen 《Journal of Agronomy and Crop Science》2014,200(1):12-23
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 CS for stomatal conductance, CT for transpiration and CLfor leaf water potential. Achachino showed significantly lower CT and CL when compared with Titicaca, implying that transpiration and leaf water potential were less affected under mild drought conditions in the Bolivian variety. CS in Achachino was significantly higher than CL and CT, 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. 相似文献
5.
6.
Md. Hasanuzzaman Lana Shabala Timothy J. Brodribb Meixue Zhou Sergey Shabala 《Journal of Agronomy and Crop Science》2019,205(2):129-140
Drought stress is a major limiting factor for crop production in the arid and semi‐arid regions. Here, we screened eighty barley (Hordeum vulgare L.) genotypes collected from different geographical locations contrasting in drought stress tolerance and quantified a range of physiological and agronomical indices in glasshouse trails. The experiment was conducted in large soil tanks subjected to drought treatment of eighty barley genotypes at three‐leaf stage and gradually brought to severe drought by withholding irrigation for 30 days under glasshouse conditions. Also, root length of the same genotypes was measured from stress‐affected plants growing hydroponically. Drought tolerance was scored 30 days after the drought stress commenced based on the degree of the leaf wilting, fresh and dry biomass and relative water content. These characteristics were related to stomatal conductance, stomatal density, residual transpiration and leaf sap Na, K, Cl contents measured in control (irrigated) plants. Responses to drought stress differed significantly among the genotypes. The overall drought tolerance was significantly correlated with relative water content, stomatal conductance and leaf Na+ and K+ contents. No significant correlations between drought tolerance and root length of 6‐day‐old seedling, stomatal density, residual transpiration and leaf sap Cl? content were found. Taking together, these results suggest that drought‐tolerant genotypes have lower stomatal conductance, and lower water content, Na+, K+ and Cl? contents in their tissue under control conditions than the drought‐sensitive ones. These traits make them more resilient to the forthcoming drought stress. 相似文献
7.
Effect of Water Stress on Physiological Attributes and their Relationship with Growth and Yield of Wheat Cultivars at Different Stages 总被引：1，自引：0，他引：1
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. 相似文献
8.
An experiment was conducted on five wheat ( Triticum aestivum L.) cultivars, C 306, PBW 175 (tolerant to water stress), DL 153-2 (moderately tolerant to water stress), HD 2428 and HD 2329 (recommended for irrigated conditions, susceptible to water stress), under pot culture conditions to study the effect of water stress on oxidative injury and antioxidant activity. Water stress significantly decreased relative water content (RWC), ascorbic acid content and membrane stability, and increased hydrogen peroxide and malondialdehyde content, a measure of lipid peroxidation, and activities of antioxidant enzymes in all the genotypes at 7, 17 and 27 days after anthesis (DAA). Water stress tolerant genotypes C 306 and PBW 175, closely followed by DL 153-2, were superior to HD 2428 and HD 2329 in maintaining high RWC, ascorbic acid content and membrane stability and lower hydrogen peroxide content and lipid peroxidation (malondialdehyde content) under water stress at the three stages. The highest activities of glutathione reductase and catalase under water stress were observed in C 306, PBW 175 and DL 153-2 and the lowest activities in HD 2428 and HD 2329 at all the stages. Superoxide dismutase activity at all stages under irrigated conditions and at the first and second stages under water stress conditions did not show significant variation among the different genotypes, but at the last stage under water stress the enzyme activity was highest in C 306, closely followed by PBW 175 and DL 153-2, and lowest in HD 2428 and HD 2329. It is apparent that water stress induces an increase in hydrogen peroxide content and consequently lipid peroxidation and membrane injury (reduced membrane stability). The degree of oxidative stress and antioxidant activity seems to be closely associated with the tolerance/susceptibility of a genotype to water stress. 相似文献
9.
为探究旱胁迫下外源ABA对玉米品种叶片光合作用以及气孔开度的影响情况,以玉米品种‘郑单988’为研究对象,采用PEG、ABA、ABA+PEG不同处理对不同时间节点下玉米苗期叶片光合作用、气孔张开程度和叶绿素含量变化进行研究。发现不同处理下3 个时间节点光合速率、蒸腾速率、气孔导度和叶绿素含量均低于对照,而气孔闭合数目均高于对照;ABA+PEG处理的4 个指标均处于PEG和ABA处理之间。说明干旱胁迫下玉米为了维持自身的生长发育,通过关闭气孔减少水分蒸腾;外施ABA可增加干旱胁迫下气孔的关闭数目和叶绿素含量,减少水分流失的同时提高旱胁迫下植株的光合速率,最终提高植株的抗旱能力。 相似文献
10.
摘要：为了揭示叶面肥“天达-2116”对烟草光合速率的影响,本试验对比分析了喷施和不喷施叶面肥“天达-2116”两种处理下,旺长期叶片的光合速率、蒸腾速率、气孔导度以及水分利用率对光强响应特征。结果表明：喷施叶面肥时烟草的光合速率、蒸腾速率、气孔导度都随光强的增强而逐渐增大。不喷施条件下,蒸腾速率和气孔导度随光强的增强而逐渐增大,而在高光强（>1200μmol s-1m-2）下,会产生光饱和现象。喷施叶面肥“天达-2116”条件下的光合速率、蒸腾速率、气孔导度均高于不喷施的,但并未改变水分利用效率。因此,适量喷施叶面肥“天达-2116”可以显著改善烟草叶片的的光合生理性状和气体交换能力。 相似文献
11.
冬小麦蒸腾效率对土壤水分响应的生理机制探讨 总被引：3，自引：0，他引：3
通过盆栽试验,研究了两种生态型冬小麦(石家庄8号和洛旱2号)在三种土壤水分条件下(L:田间持水量的60%~65%;M:田间持水量的70%~75%;H:田间持水量的80%~85%)蒸腾效率的变化及其生理机制。结果表明:随着土壤水分的降低,植株叶片水势降低,根冠比增加,两个品种间没有显著差异。土壤水分的降低,使植株生物量减少,蒸腾耗水减少,但蒸腾效率提高。L处理下石家庄8号和洛旱2号植株水平的蒸腾效率分别提高119.0%和62.2%。植株叶片光合速率与蒸腾速率随土壤水分的减少不断下降,但叶片水平的蒸腾效率提高,且与植株水平蒸腾效率呈极显著正相关(R2=0.96)。气孔导度随土壤水分的减少而降低,并与蒸腾速率呈极显著正相关(R2=0.97),表明蒸腾主要受气孔因素调节;光合速率随土壤水分减少而降低,但胞间CO2浓度升高,表明光合主要受非气孔因素调节,这种调节机制使得植株在干旱胁迫下更高效利用水分。试验结果初步揭示:光合与蒸腾调节机制的差异构成了试验品种在干旱下蒸腾效率提高的生理基础。 相似文献
12.
Plant responses to soil drying and the metabolic basis of drought-induced limitations in stomatal opening are still being discussed. In this study, we investigate the roles of root-born chemical and hydraulic signals on stomatal regulation in wheat genotypes as affected by soil drought and vapour pressure deficit. Twelve consecutive pot experiments were carried out in a glasshouse. Two bread wheat cultivars (Gönen and Basribey) were subjected to drought under high and low vapour pressure deficit (VPD) in a growth chamber. Total dry matter, specific leaf area, xylem ABA content, xylem osmotic potential, xylem pH, root water potential (RWP), stomatal conductance, leaf ABA content and photosynthetic activity were determined daily during 6 days after the onset of treatments (DAT). In the first phase of drought stress, soil drying induced an increase in the xylem ABA with a peak 3 DAT while RWP drastically decreased during the same period. Then the osmotic potential of leaves decreased and leaf ABA content increased 4 DAT. A similar peak was observed for stomatal conductance during the early stress phase, and it became stable and significantly higher than in well-watered conditions especially in high vapour deficit conditions (H-VPD). Furthermore, xylem pH and xylem osmotic potential appeared to be mostly associated with atmospheric moisture content than soil water availability. The results are discussed regarding possible drought adaptation of wheat under different atmospheric humidity. 相似文献
13.
不同水分胁迫对番茄生长的影响 总被引：27，自引：1，他引：27
番茄成苗后的生长对水分胁迫反应敏感，首先反映在茎的粗细，随着水分胁迫的减少，番茄的茎变粗，对株高和叶片数的影响的一段果以下的栽培反应不明显，水分胁迫使番茄的叶绿素含量增加，植物体内不势下降，气孔关闭，蒸腾减小，光合速率减弱，进而使产量降低，在合理用水的前提下要提高产量，三段果以下的番茄栽培应把定植后到果实膨大前这段时期的土壤水分胁迫控制在０．０４ＭＰａ左右。果实进入膨大期以后的土壤水分胁迫应控制在 相似文献
14.
V. Bala Subramanian S. Venkateswarlu M. Maheswari M. Narayana Reddy 《Journal of Agronomy and Crop Science》1993,171(5):336-342
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−2 s−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. 相似文献
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. 相似文献
15.
IR64背景耐旱导入系“PD29”分蘖期的抗逆生理特征 总被引：1，自引：0，他引：1
以轮回亲本IR64(籼稻)及旱稻材料IRAT109为对照, 系统分析了“PD29”在灌溉(对照)与干旱(胁迫)条件下的相关生理性状特征。研究发现, 遭遇干旱胁迫后, “PD29”植株能够维持较高的相对含水量(RWC)且胁迫后复水2 h该株系的RWC迅速恢复到饱和状态, 表明其具有较强的御旱能力。干旱条件下, “PD29”的PS II最大光化学效率(Fv/Fm)、渗透势(Y)、脯氨酸含量(Pro)、活性氧清除系统活性(AOA)均显著高于IR64, 且相对于灌溉处理, 其RWC, Fv/Fm的降低幅度显著低于IR64, 净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)的降幅, Pro及AOA的增幅均高于IR64。与IRAT109比较, 干旱逆境下“PD29”的Pro含量显著偏高且AOA平均增幅较高。因此认为, “PD29”的优良耐旱性表现与其在逆境下脯氨酸含量及活性氧清除系统活性的显著增强有关。另外, 干旱环境下的Pn、Gs及Tr的显著降低, 表明“PD29”的光合性能可塑性较强, 其光合性能在有利生长环境下能高效表达, 而在土壤水有限的环境下, 能够迅速降低以减少水分的进一步损失。 相似文献
16.
土壤水分胁迫对不同肥水类型冬小麦品种花后光合特性及产量的影响 总被引：3，自引：3，他引：0
为给小麦抗旱育种和节水高产栽培提供理论和技术支持,以山东省6个不同肥水类型的冬小麦品种（‘青麦6号’、‘鲁麦21’、‘烟农21’、‘烟农24’、‘济麦22’、‘良星99’）为材料,研究了水分胁迫对冬小麦花后光合特性与产量的影响及品种间差异。结果表明,在水分胁迫条件下,各冬小麦品种花后叶面积指数、旗叶叶绿素含量、净光合速率、气孔导度、蒸腾速率和水分利用效率均有所降低,产量显著下降。品种间对水分胁迫反应差异显著,其中旱地品种‘青麦6号’在水分胁迫条件下,旗叶叶绿素含量、净光合速率、蒸腾速率、水分利用效率及气孔导度均高于其他品种,产量构成因素和产量降低幅度最小,产量最高,仅比同期水分处理下降了14%。 相似文献
17.
Comparison of Salt and Drought‐Stress Effects on Maize Growth and Yield Formation with Regard to Acid Invertase Activity in the Kernels 
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下载免费PDF全文 The long‐term effects of salt stress (11 dS m?1) and drought stress (35 % WHC) were investigated for two maize genotypes, focusing on the relation between metabolic changes around the time of pollination and the impact on yield determinants at maturity. The relatively salt‐resistant hybrid Pioneer 3906 and the relatively drought‐resistant hybrid Fabregas were compared. The experiments were conducted in large plastic containers in a vegetation hall in two consecutive years (2011 and 2012). Plant height and leaf area were significantly reduced under both stress conditions. The transpiration rate was only slightly reduced under drought stress; but under salt stress, a significant reduction occurred 40–53 days after sowing. As a significant increase in sucrose concentrations was observed in the salt‐treated maize kernels 2 days after pollination, the availability of assimilates was not limiting and the plants could afford to save water by reduced stomatal opening. Although under both stress conditions the soluble acid invertase activity was reduced 2 days after pollination, concomitantly, an increase in hexose concentrations was observed. Thus, in these experiments, the delivery of hexoses by acid invertase activity did not limit kernel development. Differences in grain yield at maturity between salt and drought stress were most likely caused by salt‐specific effects (Na+ toxicity), Fabregas being more affected than Pioneer 3906. 相似文献
18.
为探明除草剂对糜子产量构成因素以及生理特性的影响,筛选适宜半干旱区糜子田使用的除草剂,以齐黍2号为试验材料,利用4种不同除草剂各设置3个浓度梯度进行糜子苗后喷施处理,研究了处理7、14和21d后糜子光合、生理特性及农艺性状的变化。结果表明,随着除草剂浓度的升高,糜子叶片的超氧化物歧化酶（SOD）活性、游离脯氨酸（Pro）和丙二醛（MDA）含量均呈上升趋势;随着除草剂胁迫时间延长,糜子叶片中SOD活性、Pro和MDA含量呈先上升后下降的变化趋势。4种供试除草剂处理后,糜子叶片的叶绿素相对含量、净光合速率、气孔导度和蒸腾速率均有不同程度降低,且都表现出一定的剂量效应。除草剂对糜子农艺性状及产量的影响不同,对主茎粗影响较小,对分蘖有促进作用,对主茎高、千粒重、主穗粒重、主穗重及产量有抑制作用。在本试验条件下,50% 2,4-D异辛酯对糜子生理及光合作用的影响较小,比较安全;苗后喷施50% 2,4-D异辛酯1000mL/hm2是糜子田除草最适剂量。 相似文献
19.
L. Duan C. Guan J. Li A. E. Eneji Z. Li & Z. Zhai 《Journal of Agronomy and Crop Science》2008,194(1):9-14
Chemical regulation using plant growth regulators has proved to be potentially beneficial in water‐saving agriculture. This experiment was conducted with winter wheat (Triticum aestivum L. cv. ‘Jingdong 6’) to study the effect of chemical regulation on alleviation of water deficit stress during the grain filling stage. Uniconazole, a plant growth regulator, was foliar sprayed at 85 % (adequate irrigation) and 60 % (deficit irrigation) field capacity. Results showed that the distribution of 3H‐H2O in roots and flag leaf, characteristics of vascular bundle in primary roots and internode below spike, roots activity, transpiration rate and stomatal conductance of flag leaf were negatively affected by deficit irrigation after flowering. Foliar spraying at the early jointing stage with 13.5 gha?1 uniconazole was able to relieve and compensate for the harmful effects of deficit irrigation. Both the area of vascular bundle in primary roots and internode below the ear were increased by uniconazole, while root viability and their ability to absorb and transport water were increased. In the flag leaf, stomatal conductance was reduced to maintain the transpiration rate and water use efficiency (WUE) measured for a single wheat plant was higher. Uniconazole increased WUE by 25.0 % under adequate and 22 % under deficit irrigations. Under adequate irrigations, the 14C‐assimilates export rate from flag leaf in 12 h (E12h) was increased by 65 % and 36 % in early and late filling stages, while under deficit irrigations, the E12h of uniconazole‐treated plants exceeded that of control plants by 5 % and 34 % respectively. Physiological damages caused by water deficiency during the grain filling stage of wheat was alleviated by foliar spraying with uniconazole. 相似文献
20.
Physiological and Biochemical Responses of Hexaploid and Tetraploid Wheat to Drought Stress 总被引：8，自引：1，他引：7
V. Chandrasekar R. K. Sairam G. C. Srivastava 《Journal of Agronomy and Crop Science》2000,185(4):219-227
An experiment was conducted to investigate the physiological and biochemical responses of two hexaploids viz., C 306 (water stress tolerant) and Hira (water stress susceptible), and two tetraploids, HW 24 (Triticum dicoccum) and A 9‐30‐1 (Triticum durum) wheat genotypes to water stress under pot culture condition. Water stress was imposed for a uniform period of 10 days at 50, 60 and 70 days after sowing (DAS) and observations were recorded at 60, 70 and 80 DAS. Total dry matter and plant height were recorded at harvest. Water stress caused a decline in relative water content (RWC), chlorophyll and carotenoid content, membrane stability and nitrate reductase activity and increased accumulation of proline at all stages and abscisic acid (ABA) at 80 DAS in all the genotypes. Both the tetraploids showed a lower reduction in RWC and highest ABA accumulation under water stress. Among the hexaploids Hira showed the most decline in RWC and the lowest ABA accumulation. The tetraploids also showed comparatively higher carotenoid content and membrane stability, closely followed by C 306, while Hira showed the minimum response under water stress. Nitrate reductase activity and chlorophyll content under irrigated conditions were highest in Hira but under water stress the lowest per cent decline was observed in C 306, followed by HW 24, A 9‐30‐1, and Hira. Proline accumulation under water stress conditions was highest in hexaploids C 306 and Hira and lowest in tetraploids HW 24 and A 9‐30‐1. Tetraploids HW 24, followed by A 9‐30‐1 maintained higher plant height and total dry matter (TDM) under water stress and also showed a lower per cent decline under stress than hexaploids C 306 and Hira. From the results it is clear that proline accumulation did not contribute to better drought tolerance of tetraploids than hexaploids. It is also apparent that water stress tolerance is the result of the cumulative action of various physiological processes, and all the parameters/processes may not be positively associated with the drought tolerance of a particular tolerant genotype. 相似文献