Soybean production can be affected by heat (HS) and water stress (WS). However, studies on effects of stresses combination under field conditions are still scarce. The objective of this study was to evaluate the impact of HS, WS and their interaction (HS × WS) during seed filling on seed weight, seed growth rate (SGR) and seed filling duration (SFD) of same phenological age pods from different canopy positions. Two soybean genotypes were exposed to four treatments during seed filling: control (irrigated plots at ambient temperature), HS (plots under temperatures >32°C for 6 hr/day during 15 days), WS (plots under 25% of soil water content, during entire seed filling) and HS × WS. Stresses interaction caused similar responses to WS alone, decreasing yield and its components (seed number and weight), as well as seed weight for each canopy position (SW_CP), SGR and SFD. Non-significant effect of irrigated HS and non-additive effects was observed in HS × WS plots, exhibiting WS a dominant effect over HS. The SW_CP strongly correlated with SGR, exhibiting upper position a trend to higher SW_CP than lower one. Seed maximum water content and pod weight, positively associated with SW_CP, indicated seed metabolic limitations under WS and HS × WS. Our results advance in the understanding of SW determination under abiotic stresses and highlight the importance of identifying pods of same phenological age to establish accurate comparisons between seeds from different canopy positions.

中文翻译：

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田间灌浆期热水胁迫下大豆种子生长动态

大豆产量会受到热 (HS) 和水分胁迫 (WS) 的影响。然而，关于野外条件下应力组合影响的研究仍然很少。本研究的目的是评估种子灌浆过程中 HS、WS 及其相互作用 (HS × WS) 对来自不同冠层的相同物候年龄豆荚的种子重量、种子生长速率 (SGR) 和种子灌浆持续时间 (SFD) 的影响职位。两种大豆基因型在种子灌浆期间接受四种处理：对照（​​在环境温度下灌溉的地块）、HS（在温度 >32°C 的地块下持续 6 小时/天，持续 15 天）、WS（地块低于 25% 的土壤含水量） ，在整个种子灌浆期间）和 HS × WS。强调相互作用对单独的 WS 产生类似的反应，降低产量及其组成部分（种子数量和重量），_CP )、SGR 和 SFD。在 HS × WS 图中观察到灌溉 HS 的非显着效应和非加性效应，表明 WS 对 HS 具有显着影响。SW _CP与 SGR 密切相关，表现出较高位置的趋势，即 SW _CP高于较低位置。种子最大含水量和豆荚重量与 SW _CP呈正相关，表明在 WS 和 HS × WS 下种子代谢受限。我们的结果促进了对非生物胁迫下 SW 测定的理解，并强调了识别相同物候年龄的豆荚以建立来自不同冠层位置的种子之间的准确比较的重要性。