叶片光合生理参数变化特征与小麦受旱状态的关系

An experiment on the drought process was set up with wheat as the test crop to study the variation characteristics of photosynthetic physiological parameters of wheat leaves during the drought process, including net photosynthetic rate (Pn), stomatal conductance (g_(ssat)), the ratio of intercellular CO₂ to air CO₂ concentration (Ci/Ca), maximum carboxylation rate (Vc_(max)) and maximum electron transport rate (J_(max)). The relationship between Pn and g_(ssat) at different stages of drought and its impact on the slope of the stomatal conductance model were also explored. The results showed that when the available soil water content (ASWC) was relatively high (>0.5), that is, under sufficient water supply conditions, the photosynthetic physiological parameters of wheat leaves remained relatively stable with the decrease of ASWC. When ASWC decreased to 0.3, the relationships between Pn, g_(ssat) and Ci/Ca remained relatively stable. When ASWC < 0.3, g_(ssat) showed a significant decreasing trend with the decrease of ASWC, and Vc_(max) and J_(max) also decreased linearly with the decrease of ASWC at this stage. Moreover, the decrease amplitude of Pn increased significantly with the decrease of g_(ssat), and the slope of the stomatal conductance model obtained by fitting also changed accordingly. When ASWC < 0.1, Ci/Ca showed an increasing trend with the decrease of ASWC, while Pn decreased with the decrease of ASWC. At this stage, Ci/Ca and Pn showed opposite variation trends. According to the variation characteristics of leaf photosynthetic physiological parameters, the drought process of wheat can be divided into four stages: the stage without or with mild drought stress, the stage where only stomatal factors affect the photosynthetic physiological process, the stage where both non - stomatal and stomatal factors affect the photosynthetic physiological process, and the stage where the photosynthetic organs are damaged.

以小麦为供试作物布设干旱过程试验,研究干旱过程中小麦叶片光合生理参数(包括净光合速率( Pn) 、气孔导度( g_(ssat) ) 、胞间CO_2与空气CO_2浓度比( Ci /Ca) 、最大羧化速率( Vc_(max) )以及最大电子传递速率( J_(max) ) )的变化特征,并探讨干旱不同阶段Pn与g_(ssat)的关系及其对气孔导度模型斜率的影响。结果表明:土壤有效含水量( ASWC)较大时( >0.5) ,即水分供给充足条件下,小麦叶片光合生理参数随着ASWC的减少保持相对稳定;而当ASWC降至0.3时,Pn与g_(ssat)及Ci /Ca的关系保持相对稳定;当ASWC<0.3时,g_(ssat)随ASWC减小呈显著降低趋势,Vc_(max)和J_(max)也在此阶段随ASWC减小而线性降低,而Pn随g_(ssat)的减小降幅明显增大,拟合所获得的气孔导度模型斜率也随之发生改变;当ASWC<0.1时,Ci /Ca随ASWC减小呈增大趋势,而Pn随ASWC减小而减小,在该阶段,Ci /Ca与Pn呈相反的变化趋势。根据叶片光合生理参数的变化特征,可将小麦受旱过程划分为4个阶段,即无干旱胁迫或干旱胁迫较轻的阶段、只有气孔因素影响光合生理过程的阶段、非气孔因素和气孔因素同时影响光合生理过程的阶段以及光合器官遭受损坏的阶段。