Abstract:

In the context of global climate change, the frequency and intensity of droughts have increased, seriously affecting agricultural production. Studies on photosynthetic characteristics and yield changes of soybean under different growth stages and different intensities of drought stress/rewatering conditions could help clarify the impacts of drought on soybean growth and the underlying mechanisms. Through water control experiments, mild drought stress (65% field water capacity) and severe drought stress (50% field water capacity) were applied to soybean at the flowering stage and the full seed stage and lasted for 7, 14, and 21 days, respectively. Rewatering was carried out after the end of the drought stress, and the rewatering level was equal to the control treatment level (80% field capacity). The results showed that drought at the flowering stage and the full seed stage reduced the maximum net photosynthetic rate (P_max) of soybean by 19.56%?70.86% and 44.38%?74.03%, respectively. At the flowering stage, the stomatal limitation value (L_s) increased but the intercellular CO₂ concentration decreased (C_i) when the drought intensity increased. The decrease of net photosynthetic rate (P_n) was dominated by stomatal factors. While at the full seed stage, the L_s first increased and then decreased, but the C_i first decreased and then increased as the drought intensity increased. Therefore, the P_n decreased induced by drought stress shifted from being dominated by stomatal factors to non-stomatal factors during the full seed stage. When the duration of drought stress was shorter (7?14 days), the water use efficiency (E_WU) of soybean increased by 6.88%?52.34%. However, when the drought lasted for a longer time (21 days), the E_WU decreased by 20.41%?61.18%. Drought reduced the yield by 15.63%?55.47% when drought occurred at the flowering stage and 24.17%?59.63% at the full seed stage. Drought led to a decrease in P_n and yield of soybean. Moreover, the drought with the same intensity had greater effects on soybean yield at the full seed stage than at the flowering stage. The E_WU could be elevated by a short-term drought, whereas the E_WU decreased when the drought lasted for a longer time.

Key words: soybean, drought stress/rewatering, flowering stage, full seed stage, net photosynthetic rate, water use efficiency, yield

摘要：

在全球气候变化背景下,干旱发生的频率和强度都有所增强,严重影响农业生产。研究大豆（Glycine max）在不同生育期不同强度干旱胁迫/复水条件下的光合特性和产量变化,可明确干旱对大豆生长发育影响并为探索灾变机制提供理论依据。通过水分控制试验,分别在开花期和鼓粒期对大豆实施轻度干旱胁迫（65%田间持水量）和重度干旱胁迫（50%田间持水量）,并分别持续7、14、21 d。在胁迫结束后进行复水,复水水平控制到对照处理水平（80%田间持水量）。结果表明,开花期和鼓粒期干旱胁迫使大豆最大净光合速率分别降低19.56%—70.86%和44.38%—74.03%。在开花期,随着干旱胁迫强度的增加,气孔限制值呈升高趋势,胞间CO₂浓度呈降低趋势,大豆净光合速率下降是由气孔因素主导。在鼓粒期,随着干旱胁迫强度的增加,气孔限制值由升高趋势转为降低趋势,胞间CO₂浓度由降低趋势转为升高趋势,大豆净光合速率下降由气孔因素主导转为非气孔因素主导。当干旱胁迫持续时间较短时（7—14 d）,大豆水分利用效率升高6.88%—52.34%,随着干旱持续时间的延长（21 d）,水分利用效率降低20.41%—61.18%。开花期干旱胁迫使大豆减产15.63%—55.47%,而鼓粒期减产24.17%—59.63%。干旱胁迫导致大豆净光合速率和产量下降,且相同程度的干旱,在鼓粒期对大豆产量的影响大于开花期;持续时间较短的干旱胁迫可提高水分利用效率,而长时间干旱胁迫使水分利用效率降低。

关键词: 大豆, 干旱胁迫/复水, 开花期, 鼓粒期, 净光合速率, 水分利用效率, 产量