A positive relationship between protein concentration and yield has been documented in different combinations of genotype and environment, often under potential conditions. However, the ecophysiological bases underlying this positive relationship under heat stress (HS) and drought stress (DS) during seed filling are still lacking. Our objective was to evaluate the relationship between seed protein content and concentration with yield in field experiments exposed to HS, DS and HS × DS interaction during the seed filling. Two field experiments were conducted and assimilates accumulation, remobilization and redistribution patterns were analysed in high and low seed protein soybean genotypes. The crop was exposed to four treatments: control (ambient temperature and soil water content near field capacity), HS (episodes above 32°C, 6 h d−1) during 15 days, DS (soil water content ≤25% of field capacity) during the whole seed filling and HS × DS. Significant and positive relationships between seed protein content and concentration with yield were observed across treatments and genotypes. Under DS and HS × DS, assimilates available during the seed filling decreased, and assimilates remobilization and partition to seeds were limited, responses significantly associated with seed protein content and concentration, and yield reductions. Furthermore, we demonstrated here that the high leaf N content at the beginning of seed filling, the short early reproductive phase duration, the high source to sink ratio and the high dry matter stem remobilization capacity, as well as the low seed number and high seed weight are intrinsic characteristics of the high protein genotype that could be associated with its high seed protein content and concentration and yield under stressful conditions. This knowledge is key to develop soybean management strategies to improve seed protein level and yield under contrasting productive scenarios.

中文翻译：

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田间高温和干旱胁迫下大豆种子蛋白浓度与产量正相关的生态生理机制

在不同的基因型和环境组合中，通常在潜在条件下，蛋白质浓度和产量之间存在正相关关系。然而，灌浆期间热胁迫（HS）和干旱胁迫（DS）下这种正相关关系的生态生理学基础仍然缺乏。我们的目的是在种子灌浆期间暴露于 HS、DS 和 HS × DS 相互作用的田间实验中，评估种子蛋白质含量和浓度与产量之间的关系。进行了两次田间试验，分析了高种子蛋白大豆基因型和低种子蛋白大豆基因型的同化积累、再动员和再分配模式。作物接受四种处理：对照（​​环境温度和土壤含水量接近田间持水量）、HS（高于 32°C、6 hd）−1）15天内，整个灌浆期的DS（土壤含水量≤田间持水量的25%）和HS×DS。在不同处理和基因型中观察到种子蛋白质含量和浓度与产量之间存在显着的正相关关系。在DS和HS×DS下，种子灌浆期间可利用的同化物减少，同化物对种子的再动员和分配受到限制，反应与种子蛋白质含量和浓度以及产量降低显着相关。此外，我们在此证明了种子灌浆开始时叶片氮含量高、早期繁殖期持续时间短、源库比高和干物质茎再利用能力高，以及种子数低和种子数高。重量是高蛋白基因型的内在特征，可能与其在胁迫条件下的高种子蛋白含量、浓度和产量有关。这些知识是制定大豆管理策略的关键，以在对比生产情景下提高种子蛋白质水平和产量。