外源钙对镉胁迫下美洲黑杨生长和生理特性的影响

Effects of Exogenous Calcium on Growth and Physiological Characteristics of Poplars under Cadmium Stress

研究外源钙(calcium,Ca)对镉(cadmium,Cd)胁迫下雌雄株美洲黑杨的生长和生理影响,探讨雌雄异株植物对Cd胁迫的响应差异,有助于了解外源钙提高植物Cd抗性的机制,可为土壤重金属污染背景下植物修复提供理论依据。采用大棚盆栽试验,研究了施加外源钙(2 g·kg^(-1))对土壤Cd(50 mg·kg^(-1)和100 mg·kg^(-1))胁迫下美洲黑杨雌、雄幼苗生长、抗氧化酶活性、光合气体交换参数及叶绿素荧光参数等生理指标的响应差异。结果显示,(1)外源钙显著提高Cd胁迫下美洲黑杨雌雄植株的超氧化物歧化酶(superoxide dismutase,SOD)活性,降低过氧化氢(hydrogen peroxide,H_(2)O_(2))含量,增强雄株的还原型谷胱甘肽(reduced glutathione,GSH)含量,其中,100 mg·kg^(-1)Cd浓度下施加外源钙显著提高雌株的GSH含量。此外,在50 mg·kg^(-1)Cd胁迫下,施加外源钙显著提高雌雄植株的过氧化物酶(peroxidase,POD)活性和雄株的过氧化氢酶(catalase,CAT)活性,使丙二醛含量(malondialdehyde,MDA)下降,说明外源钙能有效缓解Cd对美洲黑杨雌雄植株抗氧化酶系统的伤害;(2)50 mg·kg^(-1)Cd胁迫下施加外源钙显著提高美洲黑杨雌雄株的PSⅡ最大光化学效率(F_(v)/F_(m)),降低胞间二氧化碳浓度(C_(i)),雄株气孔导度(G_(s))显著上升,雌株的蒸腾速率(T r)显著提高,说明外源钙能增强植株叶片对光的捕获能力,有效缓解Cd对美洲黑杨雌雄植株光合结构的伤害;(3)与单独Cd处理相比,钙能够抑制雌雄美洲黑杨根部对Cd的吸收,最高可使根系Cd含量降低19.7%,提高Cd耐受性。综上所述,外源钙能促进光合作用,减轻氧化损伤,增强美洲黑杨幼苗对Cd胁迫的抗性;在施钙条件下,与雌株相比,雄株的抗氧化性较高,表现出较好的抗逆性。

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,photosynthetic 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)Exogenous calcium application significantly increased the activity of superoxide dismutase(SOD),decreased the content of hydrogen peroxide(H_(2)O_(2)),and enhanced the reduced glutathione(GSH)content of male and female poplars under cadmium stress.GSH content of female plants was significantly increased by the application of exogenous calcium at a concentration of 100 mg·kg^(-1)Cd.Furthermore,when subjected to 50 mg·kg^(-1)of Cd,the addition of e xogenous calcium significantly increased the peroxidase(POD)and catalase(CAT)activitys in both male and f emale 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(F_(v)/F_(m))of PSⅡand decreased the intercellular carbon dioxide concentration(C_(i))in male and female poplars.Also,the stomatal conductance(G_(s))of male plants and the transpiration rate(T r)of female plants was i ncreased.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 r esistance compared to female plants.