镉暴露条件下玉米生长及根系构型分级特征研究

Physiological effects of different Cd concentrations on maize root architecture and classification

为探究不同镉(Cd)浓度对玉米幼苗生长、Cd吸收动力学特征、根系构型及分级变化特征的影响,采用水培模拟方法,待玉米生长至两叶一心,施加不同浓度CdCl2·2.5H2O(0,5,10,25,50,100,200μmol·L^(-1)),胁迫5 d后采样并测定株高、主根长、地上地下部生物量、Cd含量和光合以及根系相关指标。结果表明,随着Cd胁迫程度的升高,玉米的株高、主根长、生物量、耐受指数、总根长、根表面积、根体积、分枝数和根尖数均显著下降,根平均直径和根冠比显著升高(P<0.05);Ⅰ~Ⅲ级(0~1.5 mm)根系分级下的根系参数(根长、根表面积和根体积)呈下降趋势,且与地下部Cd浓度呈显著负相关(P<0.05),处于0~0.5 mm径级区间的根长、根表面积和根体积所占的比例在Cd胁迫下有所降低。玉米幼苗地上地下部的Cd浓度及含量在Cd胁迫下显著提高,叶绿素含量降低,光合作用受到抑制。研究表明,Cd主要通过抑制细根的生长从而影响根系的形态发育,并抑制了光合作用的进行以及玉米地上和地下部的伸长和生物量的积累。

In this research,a hydroponics experiment was conducted to apply different concentrations of cadmium(Cd)(0,5,10,25,50,100,200 μmol·L^(-1))to maize seedlings with two leaves and one new leaf,in order to explore the effects of the different Cd concentrations on the maize seedling growth,Cd absorption kinetics and root morphology and classification.After 5 days of Cd stress,the maize seedings were sampled,the plant height,main root length,aboveground and underground biomass,root architecture,Cd content and photosynthesis and related parameters were measured.It was found that with increasing Cd stress,the plant height,main root length,biomass and tolerance index of shoots and roots,total root length,root surface area,root volume,root forks and root tips all decreased significantly;Root average diameter and root∶shoot increased significantly(P<0.05).Meanwhile root parameters(root length,root surface area and root volume)of root diameter classes designated Ⅰ-Ⅲ(0-1.5 mm)showed a decreasing trend,which had a significant(P<0.05)negative correlation with root Cd concentration.The proportion of root length,root surface area and root volume with diameter between 0-0.5 mm showed a downward trend under Cd stress.Under Cd stress,Cd concentration and accumulation in underground and aboveground parts of maize seedlings increased significantly,chlorophyll content decreased,and photosynthesis was inhibited.This study has shown that Cd affected root development mainly by inhibiting the growth and morphology of fine roots,and inhibited photosynthesis,elongation and biomass accumulation of the aboveground and underground parts of the maize seedings.