The responses of eco‐physiological processes such as leaf expansion, plant transpiration and senescence to soil water deficit have been reported to be genotype‐dependent in different crops. To study such responses in soybean (Glycine max. (L.) Merr.), a 2‐year (2017 and 2021) outdoor pot experiment was carried out on the Heliaphen automated phenotyping platform at INRAE in Toulouse (France). Six soybean cultivars (Sultana‐MG 000, ES Pallador‐MG I, Isidor‐MG I, Santana‐MG I/II, Blancas‐MG II and Ecudor‐MG II) belonging to four maturity groups (MG) commonly grown in Europe were subjected to progressive soil water deficit from the reproductive stage R1 for 17 and 23 days in 2017 and 2021, respectively. The fraction of transpirable soil water (FTSW) was used as an indicator of soil water deficit. Non‐linear regression was used to calculate FTSWt, that is, the FTSW threshold for which the rate of the eco‐physiological process in stressed plants starts to diverge from a reference value. According to FTSWt, the three eco‐physiological processes showed significant differences in sensitivity to water deficit: leaf expansion exhibits the highest sensitivity and the widest range (FTSWt: 0.44–0.93), followed by plant transpiration (FTSWt: 0.17–0.56), with leaf senescence showing the narrowest range (FTSWt: 0.05–0.16). Among six cultivars, regarding leaf expansion, Cvs Santana (FTSWt = 0.48 in 2017; FTSWt = 0.44 in 2021), Blancas (FTSWt = 0.51 in 2017; FTSWt = 0.48 in 2021) and Ecudor (FTSWt = 0.46 in 2017; FTSWt = 0.52 in 2021) in late MGs (I/II to II) exhibited higher tolerance to soil drying. Conversely, the cv. Sultana in the earliest MG (000) showed the highest sensitivity (FTSWt = 0.91 in 2017; FTSWt = 0.93 in 2021) to water deficit. However, concerning the FTSWt values for plant transpiration (0.17–0.56 in 2017; 0.19–0.31 in 2021) and senescence (0.05–0.16 in 2017; 0.06–0.16 in 2021), their range did not demonstrate a correlated trend with the MG. In addition, a negative linear correlation was observed between values of FTSWt of normalised leaf expansion at the whole‐plant level (NLE) and specific leaf area (SLA) measured on irrigated plants for both years. This suggests that genotypes with high values of SLA could be associated with higher tolerance of leaf expansion to soil water deficit. Such a non‐destructive phenotyping method under outdoor conditions could bring new information to variety testing process and provide paths for integrating genotypic variability into crop growth models used for simulating soybean eco‐physiological responses to water deficit across the plant, field and even regional scales.

中文翻译：

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不同大豆(Glycine max. (L.) Merr.)基因型叶片展开、植物蒸腾和叶片衰老对土壤水分亏缺的响应


据报道，不同作物的叶子扩张、植物蒸腾和衰老等生态生理过程对土壤水分亏缺的反应具有基因型依赖性。为了研究大豆的这种反应（大豆。 (L.) Merr.)，在法国图卢兹 INRAE 的 Heliaphen 自动表型分析平台上进行了为期 2 年（2017 年和 2021 年）的户外盆栽实验。属于欧洲常见的四个成熟组（MG）的六种大豆品种（Sultana-MG 000、ES Pallador-MG I、Isidor-MG I、Santana-MG I/II、Blancas-MG II 和 Ecudor-MG II） 2017 年和 2021 年，从生殖阶段 R1 开始，土壤逐渐缺水的时间分别为 17 天和 23 天。土壤蒸腾水分数（FTSW）被用作土壤水分亏缺的指标。使用非线性回归计算 FTSWt，即受胁迫植物的生态生理过程速率开始偏离参考值的 FTSW 阈值。根据 FTSWt，三种生态生理过程对水分亏缺的敏感性存在显着差异：叶片扩张表现出最高的敏感性和最宽的范围（FTSWt：0.44-0.93），其次是植物蒸腾（FTSWt：0.17-0.56），叶片衰老表现出最窄的范围（FTSWt：0.05–0.16）。在六个品种中，就叶片扩展而言，Cvs Santana（2017年FTSWt = 0.48；2021年FTSWt = 0.44）、Blancas（2017年FTSWt = 0.51；2021年FTSWt = 0.48）和厄瓜多尔（2017年FTSWt = 0.46；2021年FTSWt = 0.52） 2021年）在后期MG（I/II至II）中表现出更高的土壤干燥耐受性。相反，简历。最早的 MG (000) 中的苏丹娜对水分亏缺表现出最高的敏感性（2017 年 FTSWt = 0.91；2021 年 FTSWt = 0.93）。 然而，关于植物蒸腾作用（2017年为0.17-0.56；2021年为0.19-0.31）和衰老（2017年为0.05-0.16；2021年为0.06-0.16）的FTSWt值，它们的范围并未表现出与MG的相关趋势。此外，在整株植物水平（NLE）的归一化叶片扩张的 FTSWt 值与这两年在灌溉植物上测量的比叶面积（SLA）之间观察到负线性相关。这表明具有高 SLA 值的基因型可能与叶片扩张对土壤水分亏缺的更高耐受性相关。这种户外条件下的非破坏性表型分析方法可以为品种测试过程带来新信息，并为将基因型变异整合到作物生长模型中提供途径，用于模拟大豆对植物、田间甚至区域尺度缺水的生态生理反应。