Effects of Exogenous Calcium on Growth and Physiological Characteristics of Poplars under Cadmium Stress
It is significant to study effects of exogenous calcium on the growth and physiological characteristics of poplars under cadmium stress and explore the response mechanism of dioecious plants to cadmium.This can help to understand the adaptation and stress resistance differences of male and female plants under cadmium stress when exogenous calcium is applied.The results can provide a theoretical basis for selecting afforestation tree species in the context of repairing heavy metal-contaminated soil.A greenhouse pot experiment was conducted to investigate the differences in the response of physiological indicators such as growth,antioxidant enzyme activity,photosyn-thetic gas exchange parameters,and chlorophyll fluorescence parameters of poplar seedlings under cadmium stress(50 mg·kg-1,100 mg·kg-1)to exogenous calcium(2 g·kg-1)applied to the soil.The results showed:(1)Exoge-nous calcium application significantly increased the activity of superoxide dismutase(SOD),decreased the content of hydrogen peroxide(H2O2),and enhanced the reduced glutathione(GSH)content of male and female poplars un-der cadmium stress.GSH content of female plants was significantly increased by the application of exogenous cal-cium at a concentration of 100 mg·kg-1 Cd.Furthermore,when subjected to 50 mg·kg-1 of Cd,the addition of exogenous calcium significantly increased the peroxidase(POD)and catalase(CAT)activitys in both male and female plants.This resulted in a decrease in malondialdehyde content(MDA).Exogenous calcium can effectively alleviate the damage caused by Cd to the antioxidant enzyme system of male and female poplars;(2)Under the stress of 50 mg·kg-1 Cd,the application of exogenous calcium significantly increased the maximum photochemical efficiency(Fv/Fm)of PS Ⅱ and decreased the intercellular carbon dioxide concentration(Ci)in male and female poplars.Also,the stomatal conductance(Gs)of male plants and the transpiration rate(Tr)of female plants was increased.Exogenous calcium can enhance the leaf's ability to capture light which alleviated the damage caused by Cd to the photosynthetic structure of male and female plants,suggesting that calcium can play a protective role in the photosynthesis of poplars;(3)Compared to cadmium treatment alone,the application of calcium can inhibit cadmium absorption by the roots of both male and female poplars.This resulted in a reduction of up to 19.7％in cadmium content in the roots,which improved plant tolerance to cadmium.In summary,the addition of exogenous calcium can promote photosynthesis,reduce oxidative damage,and enhance the resistance of poplars seedlings to Cd stress.Under calcium application conditions,male plants exhibit higher antioxidant capacity and better stress resistance compared to female plants.
cadmium stressexogenous calciumdioecious plantgrowth and physiologycadmium contentpoplars
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