元江干热河谷区微喷灌水钾调控对柑橘光合特性影响研究OA

[Objective]Citrus is a major cash crop in the dry-hot valley of the Yuanjiang Basin,and rational water and potassium management is critical for its fruit quality.This paper presents an experimental study on the effects of water-potassium regulation under micro-sprinkler irrigation on citrus photosynthesis at the fruit swelling and maturity stages,as well as the underlying regulatory mechanisms.[Method]The experiment was conducted in an orchard of 12-year-old Bingtangcheng citrus trees from the fruit swelling and maturity stages.Sufficient irrigation combined with local standard potassium application rate served as the control(CK).There were three deficit irrigation treatments:mild water deficit(LD),moderate water deficit(MD)and severe water deficit(SD),with irrigation amount being 85%,70%and 55%of that in the CK,respectively;and two potassium fertilization treatments:applying 85%(MK)and 70%(LK)of that in the CK.During the experiment,we measured the diurnal dynamics of leaf photosynthetic parameters before and after each re-watering.Structural equation modeling was used to identify the physiological pathways through which water-potassium interaction regulates citrus photosynthesis.[Result]① After rewatering at both growth stages,the daily mean net photosynthetic rate(Pn),transpiration rate(Tr),stomatal conductance(Gs),carboxylation efficiency(CE)and instantaneous water use efficiency(WUEi)increased significantly after rewatering due to alleviation of water deficit(p＜0.001),whereas intercellular CO2 concentration(Ci)declined markedly(p＜0.001).The LD treatment was optimal for photosynthesis.②The effect of potassium application on photosynthesis varied with growing stages.MK significantly increased Pn at the swelling stage but inhibited it at the maturity stage(p＜0.001).③Stomatal behavior regulated by irrigation amount was the key limiting factor affecting photosynthesis at both the fruit swelling and maturity stages.At the fruit swelling stage,increasing potassium application increased leaf potassium content,synergistically promoting stomatal and non-stomatal processes and ultimately improving photosynthesis.At the maturity stage,increasing potassium application aggravated non-stomatal limitation,thereby inhibiting photosynthesis.[Conclusion]A combination of moderate potassium application and mild deficit irrigation(MK+LD)is optimal at the swelling stage,while mild potassium application combined with mild deficit irrigation(LK+LD)works better at the maturity stage.These irrigation and fertilization strategies improves citrus production in the study region.