Oxidative Stress and Antioxidants in Wheat Genotypes: Possible Mechanism of Water Stress Tolerance

The role of plant antioxidant systems in water stress tolerance was studied in three contrasting wheat genotypes. Water stress imposed at different stages after anthesis resulted in an increase in lipid peroxidation and a decrease in membrane stability and chlorophyll and carotenoid contents. The antioxidant enzymes ascorbate peroxidase, glutathione reductase and non-specific peroxidase also increased significantly under water stress. Genotype PBW 175, which had highest ascorbate peroxidase, glutathione reductase and peroxidase activity, had the lowest lipid peroxidation (malondialdehyde content) and highest membrane stability and contents of chlorophyll and carotenoids under water stress, while the susceptible genotype WH 542 exhibited the lowest antioxidant enzyme activity, membrane stability and contents of chlorophyll and carotenoids and the highest lipid peroxidation. Genotype HD 2402 showed intermediate behaviour. It seems that drought tolerance of PBW 175, as represented by higher membrane stability and chlorophyll and carotenoid contents and lower lipid peroxidation, is related to its higher antioxidant enzyme activity.     

Water Stress Tolerance of Wheat (Triticum aestivum L.): Variations in Hydrogen Peroxide Accumulation and Antioxidant Activity in Tolerant and Susceptible Genotypes

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.     

Physiological and Biochemical Responses of Hexaploid and Tetraploid Wheat to Drought Stress

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.     

外源褪黑素对干旱胁迫下玉米幼苗的影响

为了研究外源褪黑素在增强干旱胁迫下玉米幼苗生长适应性中的作用,降低干旱胁迫对玉米幼苗的伤害。以‘郑单958’玉米种子为试验材料,采用人工控水法,设置6组处理（CK、干旱、M1、M2、M3、M4）研究了干旱胁迫下,外源褪黑素对玉米幼苗生长指标、叶绿素含量、脯氨酸以及过氧化物酶活性的影响。试验结果表明,褪黑素有利于缓解干旱胁迫对玉米幼苗的影响,如株高、叶片含水量、根长,提高了干旱胁迫下玉米幼苗叶绿素合成能力,SPAD值升高;褪黑素可以缓解干旱对玉米幼苗的氧化胁迫,通过提高抗氧化酶活性,随着干旱胁迫天数的增加,各处理组过氧化物酶活性明显高于干旱组;脯氨酸含量随干旱胁迫天数增加而增高,干旱胁迫7天后,干旱组和其他处理组间脯氨酸含量存在显著差异。综合来看,外源褪黑素能提高干旱胁迫下玉米幼苗生长能力,主要通过提高抗氧化酶活性和叶绿素合成,降低膜脂过氧化水平。外源褪黑素能提高玉米抗旱性,可以作为植物生长调节剂应用到实际生产中。     

Improved Cold and Drought Tolerance of Doubled Haploid Maize Plants Selected for Resistance to Prooxidant tert‐Butyl Hydroperoxide

To improve the abiotic stress tolerance of maize (Zea mays L.), doubled haploid (DH) plants were produced by in vitro selection of microspores exposed to tert‐butyl hydroperoxide (t‐BuOOH) as a powerful prooxidant This study investigated the tolerance of the progenies of t‐BuOOH‐selected DH lines to oxidative stress, cold and drought in controlled environment pot experiments by analyses of photosynthetic electron transport and CO₂ assimilation processes, chlorophyll bleaching and lipid peroxidation of leaves. Our results demonstrated that the t‐BuOOH‐selected DH plants exhibited enhanced tolerance not only to oxidative stress‐induced by t‐BuOOH but also to cold and drought stresses. In addition, they showed elevated activities of antioxidant enzymes such as superoxide dismutase, ascorbate peroxidase, catalase, glutathione reductase and glutathione S‐transferase when compared with the DH lines derived from microspores that were not exposed to t‐BuOOH and to the original hybrid plants. The results suggest that the simultaneous up‐regulation of several antioxidant enzymes may contribute to the oxidative and cold stress tolerance of the t‐BuOOH‐selected DH lines, and that the in vitro microspore selection represents a potential way to improve abiotic stress tolerance in maize.     

Screening of Barley Varieties for Drought Resistance

Barley varieties were screened for their efficient drought enduring ability and associated characters which may be useful in breeding programmes. The characters studied were: relative water content, content of proline, chlorophyll stability index (CSI), and percentage grain loss per plant due to water stress subjected to 10 days from jointing to boot stage. Proline and chlorophyll stability index were greatly associated with drought response (r =+0.54; -0.49), flag leaf area (r =+0.69; -0.51) and, to a certain extent, with leaf number (r = -0.35 and +0.34). Among the studied 19 varieties of barley, only three (DL 192, DL 36, DL 3) showed high enduring ability, of these the former two fall in the early, and the last one in the late flowering group. Morphological architecture of DL 192 had gathering type tiller (narrow tiller angle), wider and floppy leaves and it also bears physiological characters (high proline and high relative water content, and low value of chlorophyll stability index) necessary for drought resistance. DL 3 and DL 36 had dispersing type tiller (wider tiller angle) and erect leaf with good leaf area/plant, but unit leaf area was low in DL 3 (relates with shading behaviour reducing water loss). Other relations of drought resistance are briefly discussed in the text. An appraisal of the various traits revealed that high proline content, and low CSI (biochemical characters), earliness, larger flag leaf area and fewer leaves per plant (morphological characters) were directly correlated with productivity of the cultivars under drought conditions. These characters could be used as a guideline for breeding drought resistant cultivars of barley.     

Morphological and biochemical responses of Balanites aegyptiaca to drought stress and recovery are provenance‐dependent

Balanites aegyptiaca is a drought‐tolerant tree naturally distributed in Africa and has a high potential for biofuel production and livelihood. To understand the plant tolerance to drought stress, B. aegyptiaca plants collected from five provenances were subjected for 4 weeks to drought stress through different regimes of soil volumetric water content (VWC, i.e. 25% control, 15% as moderate and 5% as a severe drought stress) followed by 2‐week recovery. Morpho‐physiological responses as well as the changes in antioxidant defences under water stress and recovery were investigated. Drought stress significantly reduced plant biomass‐related parameters, stomatal conductance, quantum efficiency and increased leaf temperature. Each provenance showed specific patterns of stress response reactions that were detected in a cluster analysis. The large leaf area and a high level of lipid peroxidation in Cairo provenance increased its sensitivity to severe drought. For provenances El‐Kharga and Yemen, the highest tocopherol contents and the highest catalytic activities of ascorbate peroxidase (SOD), catalase (CAT), glutathione reductase (GR) and dehydroascorbate reductase (DHAR) were recorded. These traits contributed to the high drought tolerance of these two provenances in comparison with the other provenances. All plants recovered from stress and showed specifically increased activity of glutathione‐S‐transferase (GST) as a repair mechanism. Results showed that the drought tolerance level in B. aegyptiaca is provenance‐dependent.     

干旱胁迫对内蒙古草原多根葱生理生化指标的影响

为了探明内蒙古草原多根葱抗旱性能,采用盆栽控水法研究干旱胁迫对多根葱植物叶片生理生化指标的影响。结果表明,随着干旱胁迫时间的延长,内蒙古草原3个样地(Ⅰ、Ⅱ、Ⅲ)多根葱叶片相对含水量呈显著下降的趋势,叶绿素含量、SOD、POD、CAT活性均呈先上升后下降的趋势,水分饱和亏、相对电导率、脯氨酸、丙二醛含量呈上升的趋势。多根葱干旱性程度与水分饱和亏、相对电导率、膜脂过氧化作用呈正相关,与叶绿素含量、相对含水量、保护性酶活性呈负相关。隶属函数法抗旱性综合评价耐旱性强弱顺序为ⅠⅢⅡ。     

GSH/GSSG对盐胁迫下番茄幼苗谷胱甘肽化修饰和抗氧化系统的影响

以营养液栽培'中蔬四号'番茄(Solanum lycopersicum Mill.)为研究材料,研究不同时期的盐胁迫下叶面喷施5 mmol/L还原型谷胱甘肽(reduced glutathione,GSH)和1 mmol/L γ-谷氨酰半胱氨酸合成酶抑制剂(inhibitor of gamma-glutamylcyst...     

褪黑素浸种对盐碱胁迫下大豆种子萌发的影响

为研究褪黑素浸种对盐碱胁迫下大豆种子萌发的影响,以大豆品种垦丰16为试验材料,研究100μmol/L褪黑素浸种对不同浓度混合盐碱（NaCl和NaHCO₃物质的量按1:1混合,配制为0、25、50、100、200mmol/L的盐碱溶液）胁迫下大豆种子萌发的影响。结果表明：与对照相比,随盐碱浓度提升,大豆种子发芽率、发芽指数、芽鲜重和芽干重呈不断降低趋势,超氧化物歧化酶、过氧化物酶、过氧化氢酶、谷胱甘肽还原酶和谷胱甘肽过氧化物酶活性呈现先升高后降低的趋势,抗坏血酸过氧化物酶活性呈不断上升趋势;渗透调节物质可溶性糖、可溶性蛋白和脯氨酸含量呈现先升高后降低的趋势;膜脂过氧化产物丙二醛、H₂O₂含量、$\mathop{{O}}_{2}^{{\mathop{}_{\ .}^{-}}}$产生速率呈不断上升趋势。褪黑素浸种可提高不同浓度盐碱胁迫下大豆种子发芽率、发芽指数、芽鲜重、芽干重和抗氧化酶活性以及渗透调节物质含量,降低丙二醛、H₂O₂含量和$\mathop{{O}}_{2}^{{\mathop{}_{\ .}^{-}}}$产生速率。综上所述,褪黑素浸种可以缓解不同浓度盐碱胁迫对大豆种子发芽的抑制作用,并能提高抗氧化酶活性和渗透调节物质含量,降低膜脂过氧化程度。     

Salicylic Acid and Abiotic Stress Responses in Rice

Among plant species rice (Oryza sativa L.) leaves can be characterised with a very high level of salicylic acid content; however, its exact role is still poorly understood. In the present work, rice genotypes with different levels of drought tolerance have been subjected to PEG‐induced drought or cold stress at 10 °C in order to find relationship between the salicylic acid metabolism and the level of stress tolerance; and between the salicylic acid level and other protective mechanisms. Although the drought‐sensitive genotypes usually contained slightly higher amount of salicylic acid than the tolerant ones, there was no strong correlation between the salicylic acid contents and the degree of drought tolerance. Because the expression pattern of the chorismate synthase and isochorismate synthase genes did not correlate with the level of salicylic acid, but there was a correlation between the levels of salicylic acid and ortho‐hydroxy‐cinnamic, it is assumed that the salicylic acid synthesis via ortho‐hydroxy‐cinnamic acid may play a more decisive role than the chorismate–isochorismate–salicylic acid pathway in rice. While the activity of the glutathione reductase enzyme did not show correlation with drought tolerance, the glutathione S‐transferase activities were usually higher in the leaves of the drought‐tolerant varieties than in the sensitive ones. The salicylic acid contents in the leaves were not substantially affected by the applied stress conditions; however, other stress‐related compounds polyamines showed marked, stress‐specific responses. Correlation data suggest that there is no direct link between the abiotic stress‐induced polyamine changes and the salicylic acid metabolism in rice.     

Antioxidative Response of Quinoa Exposed to Iso‐Osmotic,Ionic and Non‐Ionic Salt Stress

Antioxidants play an important role in adapting plants to abiotic stress by detoxifying reactive oxygen species (ROS). Involvement of antioxidant enzymes in abiotic stress tolerance of highly stress‐tolerant quinoa was studied in a climatic chamber at 6 mOsm (milliosmolar) ionic (300 mm NaCl) and non‐ionic (600 mm mannitol) salts combined with increasing levels of potassium K1 and K2 (6, 12 mm ), respectively. Fifteen days of salt treatment (both ionic and non‐ionic) decreased plant growth (shoot and root fresh weight), stomatal conductance and chlorophyll content index. Furthermore, both forms of salt stress increased the activities of superoxide dismutase, catalase, ascorbate peroxidase and peroxidase up to 2.33‐, 3.98‐, 4.78‐ and 5.55‐folds, respectively, compared to no salt treatment, whereas membrane stability index decreased corresponding to increase in lipid peroxidation (malondialdehyde), with salt treatments compared to non‐stressed plants. However, no significant effect of potassium and salt treatments has been noticed on the maximal photochemical efficiency of PSII. The results suggested that enhanced antioxidant enzymes activity under salt stress could be one of the factors responsible for abiotic stress tolerance in quinoa.     

拔节期干旱对不同玉米品种叶片生理特性的影响及抗旱性分析

为筛选玉米抗旱品种及探究抗旱机制。本研究以目前主推的6个玉米品种为试验材料,在拔节期进行水分中度胁迫试验,分析干旱胁迫下6个玉米品种的丙二醛含量、叶绿素含量、可溶性蛋白含量、脯氨酸含量、超氧化物歧化酶和过氧化物酶活性。发现6个玉米品种在干旱胁迫下表现出了不同的生理响应机制,6个玉米品种叶片的丙二醛含量、叶绿素含量均不同幅度的显著下降,脯氨酸含量、可溶性蛋白含量、超氧化物歧化酶和过氧化物酶活性均不同程度的显著升高。干旱胁迫下,尤其‘郑单988’和‘郑单6386’的MDA含量升高幅度较低,叶绿素含量下降幅度较小,抗氧化酶活性升高幅度较大,可溶性蛋白和脯氨酸含量较高;相反‘郑单958’相对于‘郑单6386’和‘郑单988’,生理生化层面表现出较弱的抗旱性。结果表明拔节期‘郑单988’和‘郑单6386’的抗旱性较‘郑单958’强。本研究结果对揭示玉米耐旱机理有一定的重要意义,并可以为玉米耐旱种质筛选、改良和分子育种提供有效的指导和参考。     

Response of Antioxidant Enzymes,Phytochelatins and Glutathione Production Towards Cd and Zn Stresses in Cajanus cajan (L.) Millsp. Genotypes Colonized by Arbuscular Mycorrhizal Fungi

Most metal polluted natural environments are contaminated with multiple metals, and arbuscular mycorrhizal (AM) fungi are among the extracellular strategies to avoid metal toxicity. To understand the interaction between Cd, Zn and AM fungi Glomus mosseae, two genotypes (Sel 85N and P792) of pigeonpea (Cajanus cajan L. Millsp.), differing in their metal tolerance, were chosen for study. Results revealed that root dry weights were more severely affected than shoot dry weights as both the metals were accumulated in roots than in the aerial parts. Mycorrhization promoted biomass yields by decreasing metal content in plant tissues. Exposure to the metals resulted in oxidative burst (high H₂O₂, malondialdehyde contents and electrolyte leakage), which was accompanied by decreased membrane stability. However, increase in the level of total non‐protein thiols (TNP‐SH) and the activity of antioxidant enzymes like superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) and glutathione reductase (GR) suggested that all these parameters were synergistic in combating heavy‐metal‐induced oxidative stress. Zn supplementation proved to be inhibitory for Cd‐induced oxidative stress. AM fungi alleviated oxidative stress through enhanced production of TNP‐SH as well as through upregulation of antioxidant enzymes. Sel 85N exhibited lesser oxidative damage and more efficient defence mechanism than P792.     

燕麦耐盐性的生理生化指标网络分析

为探讨盐胁迫下燕麦幼苗耐盐性与生理生化指标之间的关系,采用沙培法对6个栽培燕麦品种进行盐胁迫处理（0、1、2、4、6、8g/kg NaCl）,在播种7、14、21d时测定各处理下幼苗的生长指标和生理生化指标,并用单因素方差、相关性网络、隶属函数等方法进行数据分析。结果表明,耐盐指标间存在显著正相关关系,过氧化物酶活性、叶绿素含量与耐盐指标间存在显著正相关,丙二醛、可溶性糖、脯氨酸含量与耐盐指标间存在显著负相关;种子千粒重与耐盐指标、过氧化物酶及叶绿素含量之间存在显著负相关关系。     

一氧化氮和亚甲基蓝对盐胁迫抗虫棉根系的抗氧化能力的影响

 通过检测抗氧化酶活性和抗氧化物含量,研究一氧化氮和亚甲基蓝对盐胁迫抗虫棉根系的抗氧化能力的影响。在正常条件和盐胁迫条件下分别用一氧化氮和亚甲基蓝处理抗虫棉幼苗,检测抗坏血酸(ASA)含量、抗坏血酸过氧化物酶(APX)活性、谷胱甘肽还原酶(GR)活性、谷胱甘肽(GSH/GSSG)值、脱氢抗坏血酸还原酶(DHAR)活性、单脱氢抗坏血酸还原酶(MDAR)活性,并作对比。结果表明：正常生长条件下添加NO能促进棉花幼苗生长,而添加亚甲基蓝(MB)显著抑制抗虫棉幼苗的生长;添加NO显著缓解了盐胁迫对棉花幼苗生长的抑制,提高了根系的抗氧化能力,盐胁迫下添加NO的同时添加MB可不同程度地降低以上抗氧化物质含量和抗氧化酶活力,解除NO对盐胁迫的促长作用。     

干旱胁迫对盆栽“川丹参1号”生理指标及主要活性成分含量的影响

采用聚乙二醇（PEG-6000）对盆栽“川丹参1号”（CDS-1）模拟长期干旱胁迫,研究干旱胁迫对其生长情况、生理指标及主要活性成分积累的影响。结果表明,干旱胁迫显著降低CDS-1叶片中叶绿素含量,可溶性蛋白、可溶性糖和脯氨酸含量随干旱程度增加呈上升趋势,干旱胁迫下丙二醛含量显著增加,抗氧化酶（SOD、POD和CAT）活性随干旱胁迫程度增加而增加。活性成分分析表明,干旱胁迫后CDS-1根中酚酸和丹参酮类含量均有所上升,迷迭香酸和丹酚酸A含量在PEG-6000浓度为150g/L时最高,分别为CK的145%和175%,丹参酮类含量在PEG-6000浓度为50g/L时最高,增幅超60%。CDS-1在干旱胁迫下表现出适应性变化,轻度和中度干旱胁迫（PEG-6000浓度为50~100g/L）有利于CDS-1中酚酸和丹参酮类活性成分的积累,在实际生产中可通过科学控水保证和提高丹参药材的品质。     

Drought effects on yield and its components in Indian mustard (Brassica juncea L.)

Effects of drought on yield and yield components were investigated during the spring season 2000–2001 by growing 14 Indian mustard genotypes under irrigated and rain-fed conditions at Bharatpur and Jobner. A disease and pest management schedule was followed when required. The drought susceptibility index (DSI) for seed yield and component characteristics was calculated to characterize the relative tolerance of genotypes. Plant height, primary branches, secondary branches per plant, 1000-seed weight and seed yield were reduced under rain-fed conditions. The top five genotypes at Bharatpur that showed tolerance to moisture stress for seed yield, as indicated by their lowest DSI, were, in descending order PSR-20, PRO-97024, JMMWR-941, IS-1787 and PCR-7, whereas at Jobner these were JMMWR-941, RC-1446, PSR-20, RH-819 and 'Varuna'. Of these, PSR-20 and JMMWR-941 were among the top six at both locations. These genotypes also showed relatively low DSI for one or more characteristics, such as primary branches per plant, secondary branches per plant, harvest index and seed : husk ratio. Genotypes with the lowest DSI, particularly for seed yield at both locations, would serve as useful donors in the breeding programme for improving the drought tolerance of existing Indian mustard cultivars.     

外源水杨酸对干旱胁迫下花椰菜叶片抗氧化作用的影响

以花椰菜为试材,采用大田人工控水设置田间持水量的35%、50%和65% 3个灌水下限,通过叶面喷施0.1 mmol/L水杨酸(SA),研究外源SA对花椰菜叶片抗氧化能力的影响。结果表明：SA可提高叶片超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)和抗坏血酸过氧化物酶(APX)等抗氧化酶活性,同时减缓花椰菜叶片中丙二醛(MDA)积累和细胞膜透性的持续增大,增加游离脯氨酸(Pro)和还原型谷胱甘肽(GSH)在叶片中的积累。因此,SA能够提高干旱胁迫下花椰菜的抗旱能力,提高花椰菜叶片中抗氧化物质的活性,增加渗透调节物质的含量,减少膜脂过氧化作用,在一定程度上可缓解干旱对植物造成的伤害。     

Drought stress‐induced changes in starch yield and physiological traits in potato

Drought stress is an important limitation for potato (Solanum tuberosum L.) production as potato depends on appropriate water availability for high yields of good quality. Therefore, especially in the background of climate change, it is an important goal in potato breeding to improve drought stress tolerance. In this study, 34 European starch potato cultivars were evaluated for drought stress tolerance by growing under well‐watered and long‐term drought stress conditions in rainout shelters in 2 years’ pot trials. Besides yield, six physiological traits, that is free proline content, osmolality, total soluble sugar content, chlorophyll content (SPAD), cell membrane stability and crude protein content, were determined in leaves sampled during vegetative growth and during flowering to investigate their association with drought tolerance. ANOVA revealed significant treatment effects for all physiological traits and increased genotypic effects at flowering. The sensitivity of physiological traits to drought was significantly higher during flowering than during vegetative growth. Drought stress decreased starch yield significantly (p < .001), on average by 55%. Starch yield was significantly influenced by genotype and genotype × treatment interactions. Stress tolerance index (STI) calculated from starch yield ranged from 0.26 (sensitive) to 0.76 (tolerant) with significant genotype effects (p ≤ .001). STI correlated positively with cell membrane stability (r = .59) and crude protein content (r = .38) and negatively with osmolality (r = ?.57) and total soluble sugar content (r = ?.71). These contrary correlations suggest a dual adaptation strategy in potato under long‐term drought stress conditions including increased membrane stability combined with an increased osmolality due to an increased soluble sugar content.