Characteristics of Photosynthesis-transpiration Coupling of Wheat Leaves under Different Water Treatments and Their Regulation Mechanism
Leaves regulate stomata to closely couple the processes of plant carbon assimilation and water consumption,but it is unclear whether this carbon-water coupling relationship changes under different water conditions.This study selected spring wheat,a field crop in the semi-arid region of northwest China,as the research object.Four water treatments were applied:sufficient water supply(CK),mild drought(T1),moderate drought(T2),and severe drought(T3).Leaf photosynthesis and transpiration were observed on typical sunny days during the wheat jointing period(8:00-18:00).Results showed that air temperature(t)and photosynthetic active radiation(PAR)exhibited unimodal patterns with peaks at 12:00 and 16:00.Leaf stomatal conductance(Gs)showed bimodal distributions under CK,T1,and T2,while no obvious daily change was observed under T3.The transpiration rate(Tr)exhibited bimodal changes under T1 and T2,but unimodal changes under CK and T3.The daily variation of photosynthetic rate(Pn)decreased from sufficient water to severe drought treatments,with greater fluctuations before 12:00 and a gradual decrease thereafter.Significant positive correlations were observed between photosynthesis and transpiration under all water treatments.The main regulatory factor for Pn under CK was PAR,while under T1 and T3,it was Gs.The main regulatory factor for Tr under CK and T1 was PAR,while under T2 and T3,the primary positive regulator was Gs and the negative regulator was t.The slope of the Pn-Tr relationship indicated differences in carbon-water coupling characteristics under different water treatments,with severe drought significantly reducing the coupling.These findings provide a reference for carbon-water coupling simulations under drought conditions.
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