Water deficit is the most limiting factor for seed yield of crop species in the arid and semi-arid regions. Due to increasing limitation of fresh water resources and importance of safflower (Carthamus tinctorius L.) as a significant oilseed crop in Iran, it is necessary to evaluate physiological responses of drought tolerance and its association with seed yield of this crop in water stress condition. In this study, 21 safflower genotypes were planted by hand in the field under water stress and non-stress conditions in a randomized complete block design with two replications during 2 years (2016–17). The results indicated that water deficit stress significantly reduced relative water content (RWC), chlorophyll a (Chl-a) and chlorophyll b (Chl-b) concentrations and seed yield, but increased ascorbate peroxidase (APX) and peroxidase (POX) activities and leaf proline concentration. Significant differences were observed among the genotypes for all studied traits except Chl-b concentration. Genotypes were discriminated according to their response to drought using stress tolerance index (STI). Drought tolerant genotypes displayed a higher capability for accumulation of proline in association with maintaining RWC, antioxidant enzymes activity and higher seed yield, compared to the drought sensitive genotypes. Presented results suggested that safflower genotypes with higher levels of antioxidant enzymes activity, RWC and proline accumulation are characterized by a higher STI. Therefore, these physiological traits can be employed as effective criteria for selecting safflower genotypes with more tolerance to water deficit stress.

中文翻译：

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生理性状在采用红花 (Carthamus tinctorius L.) 基因型对缺水条件下的有效性

缺水是干旱和半干旱地区作物种子产量的最大限制因素。由于淡水资源的日益限制和红花（Carthamus tinctorius L.）作为伊朗重要油料作物的重要性，有必要评估干旱耐受性的生理反应及其与该作物在水分胁迫条件下种子产量的关系。在这项研究中，21 种红花基因型在水分胁迫和非胁迫条件下以随机完整区组设计在田间手工种植，并在 2 年（2016-17 年）期间进行了两次重复。结果表明，缺水胁迫显着降低了相对含水量（RWC）、叶绿素 a（Chl-a）和叶绿素 b（Chl-b）浓度和种子产量，但增加抗坏血酸过氧化物酶 (APX) 和过氧化物酶 (POX) 活性和叶脯氨酸浓度。除 Chl-b 浓度外，所有研究性状的基因型之间均观察到显着差异。使用胁迫耐受指数（STI）根据对干旱的反应来区分基因型。与干旱敏感基因型相比，耐旱基因型表现出更高的脯氨酸积累能力，与维持 RWC、抗氧化酶活性和更高的种子产量相关。结果表明，具有较高水平抗氧化酶活性、RWC 和脯氨酸积累的红花基因型具有较高的 STI。所以，