[Objective]To investigate photosynthetic,physiological and biochemical characteristics of Aronia melanocarpa seedlings under natural soil drought.[Method]A study was conducted using 3-year-old potted seedlings as experimental materials.The continuous drought treatment was applied through natural drying method.The dynamic changes in leaf water parameters,photosynthesis and chlorophyll fluorescence parameters,protective enzyme activity,and osmoregulation substance content under continuous drought conditions were monitored.Correlation analysis and principal component analysis were conducted on these physiological parameters.[Result]During the natural drought process,a significant decrease in the relative water content(RWC)of leaves was observed,accompanied by a notable increase in water saturation deficit(WSD).As soil moisture decreased,an initial increase in the content of photosynthetic pigments,including Chl a,Car,and total chlorophyll was observed,followed by a subsequent decline.Soil moisture content decreased from 80%-75% (CK)to 40%-35% (T3)of field capacity,net photosynthetic rate(Pn),stomatal conductance(Gs),and transpiration rate(Tr)of A.melanocarpa seedlings gradually decreased;however,water use efficiency(WUE)increased significantly.It was worth noting that there was no significant difference observed in PSⅡmaximum photochemical efficiency(Fv/Fm)compared to the control group.As soil drought intensified,the decline Pn,Gs,Tr,and Fv/Fm became more pronounced,while Ci exhibits a noticeable increased.By observing the trends and correlations among leaf Pn,Gs,Ci,and Fv/Fm.It could be inferred that stomatal limitation was the main factor affecting the photosynthetic characteristics of A.melanocarpa during early to mid-drought period.However,non-stomatal limitations became prominent in the later stages.As drought conditions intensify,the integrity of leaf membranes was compromised,resulting in a significant increase in electrolyte leakage rate;Initially,the content of MDA and H2O2 as well as activities of superoxide dismutase(SOD),peroxidase(POD),and catalase(CAT)exhibited an increase followed by a subsequent decrease;Simultaneously,there was a gradual accumulation of osmoregulation substances.Through comprehensive analysis of the relationships among various indicators,it was observed that significant correlations exist not only within individual parameters but also between water availability,photosynthetic parameters,protective enzyme activity,and osmotic adjustment substances.[Conclusion]Based on the results of principal component analysis and evaluation of measurement indicators,These findings suggest that A.melanocarpa responds to drought stress by rapidly reducing stomatal conductance to minimize water loss and enhance water use efficiency.Additionally,It maintains normal functioning of PSⅡin photosynthetic structure by increasing certain pigment contents to adapt to drought conditions.Furthermore,it demonstrates a strong ability to cope with drought stress by regulating protective enzyme activity and increasing osmoregulatory substance content as a means of mitigating damage caused by drought stress.
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