火炬树幼苗对镉胁迫的生理响应及积累特性

Effects of Cd^2+ on the physiological response and accumulation characteristics of Rhus typhina

采用室内盆栽法研究不同浓度Cd^2+(0、25、50、75、100 mg·kg^-1)处理对火炬树生长指标、生理活性和光合特性的影响,探讨火炬树对Cd2+胁迫的耐受程度及适应能力.结果表明:随着Cd2+浓度的升高,火炬树幼苗的株高、主根长、地上和地下部分生物量受到显著抑制(P<0.05);MDA含量随着胁迫程度的增加而升高,可溶性蛋白含量呈先升高后降低趋势.叶绿素含量、类胡萝卜素含量、光合作用气体交换参数、叶绿素荧光参数均随Cd^2+浓度的升高不断下降,与生长量变化规律一致.但在低浓度Cd^2+(25 mg·kg^-1)胁迫下,火炬树主根长、株高、净光合速率(Pn)、气孔导度(Gs)的降幅较小(P>0.05),叶绿素各指标与对照相比差异不显著(P>0.05),初始荧光(Fo)和最大荧光(Fm)同时上升,表明PSⅡ反应中心未被破坏;MDA和可溶性蛋白含量增加,幼苗单株Cd2+积累量最高为19.38 mg·kg^-1,转移系数为0.29,高于其他处理组.说明在低浓度Cd2+胁迫下,火炬树幼苗能通过调节生理活性来减轻Cd^2+对细胞的毒害,维持正常的生长和光合作用,对Cd^2+胁迫具有一定抗性.

Pot experiments were conducted to investigate the growth, physiological response and photosynthetic characteristics of Rhus typhina grown in soils contaminated with different levels of cadmium(Cd2+)(0, 25, 50, 75 and 100 mg·kg-1). The results showed that the height, main root length, aboveground and underground biomass of R.typhina were increasingly inhibited as Cd2+ stress got intensified(P<0.05). Malondialdehyde(MDA) contents rose while soluble protein increased firstly and then declined with increasing Cd2+ stress. Meanwhile chlorophyll content, carotenoid content, photosynthetic gas parameters and chlorophyll fluorescence parameters all showed various degrees of downward trends, which were in line with changes in plant growth. However, under slight Cd^2+ stress, the height, taproot length, net photosynthetic rate(Pn) and stomatal conductance(Gs) of R.typhina were not significantly reduced compared with the control(P>0.05). There was neither significant difference in chlorophyll indexes compared with the control(P>0.05). Minimal fluorescence(Fo) and maximal fluorescence(Fm) rose at the same time, indicating that the reaction center of PSⅡ was not damaged. The increases of MDA and soluble protein also showed that R.typhina could mitigate the poison on cells caused by Cd^2+ through adjusted physiological activities. Meanwhile, the accumulated Cd^2+ for seedlings reached 19.38 mg·kg^-1, with translocation factor being 0.29, slightly higher than those of other treatments. Thus, R.typhina can function and photosynthesize normally under light Cd^2+ stress at 25 mg·kg^-1, which has potential application in remediating soils polluted by Cd^2+.