藿香蓟的镉积累、生物量及叶绿素荧光参数对不同梯度镉胁迫的响应

Biomass, cadmium accumulation and chlorophyll fluorescence parameters response of Ageratum conyzoides to different concentrations of cadmium stress

关键词:  Cd  藿香蓟  生物量  积累  叶绿素荧光参数

Key words:  cadium  Ageratum conyzoides  biomass  accumulation  chlorophyll fluorescence parameters

摘要:

通过盆栽试验,研究藿香蓟(Ageratum conyzoides)的地上部和地下部Cd含量、干重、转运系数、根冠比及叶片叶绿素荧光参数对不同梯度Cd胁迫的响应。结果表明:随Cd胁迫浓度增加,藿香蓟转运系数逐渐降低,地上部和地下部Cd含量随Cd胁迫浓度的增加而逐渐升高,在Cd(300 mg·kg^-1)胁迫下,植株地上部Cd含量为125.50 mg·kg^-1,这一结果已超过Cd超富集植物的临界值(100 mg·kg^-1); 植株地上部及地下部干重随Cd胁迫浓度的增加均逐渐降低,且中、高浓度Cd胁迫对植物的生长具有显著的抑制作用,各处理间的根冠比呈上升趋势并比对照高,可见高浓度Cd胁迫可阻碍根系的生长,从而影响植物地上部对营养和水分的吸收,最终抑制植株生长及生物产量的提高; PSⅡ的最大光化学效率(Fv/Fm)、PSⅡ的潜在光化学效率(Fv/Fo)随着Cd胁迫浓度的增加均逐渐升高,初始荧光(Fo)和最大荧光(Fm)均逐渐降低,光量子产量(ФPSⅡ)、电子传递效率(ETR)、光化学猝灭系数(qP)及非光化学猝灭系数(qN)均出现先升后降的趋势; Cd胁迫扰乱叶片正常时期的光合特性及延缓植株衰老,但各处理间的叶绿素荧光动力学参数差异不显著,Cd胁迫对叶片PSⅡ反应中心的电子传递、光化学反应及散热能力影响较弱; 高浓度Cd胁迫明显抑制植株的生长,但植株地上部及地下部的Cd积累能力较强,可作为植物修复重金属污染土壤的备选植物并用来治理Cd污染的土壤。

Abstract:

The pot experiments was conducted to investigate the above ground Cd content,below ground Cd content,transfer factor,above ground dry weight,below ground dry weight,ratio of root to shoot and chlorophyll fluorescence parameters response of Ageratum conyzoides to different concentrations of Cd stress. The results showed that the transfer factor of A. conyzoides decreased gradually with Cd concentration increasing. However,the above ground Cd contents and below ground Cd contents increased gradually with Cd concentration increasing. It reached 125.50 mg·kg^-1 at the Cd concentrations stress which was 300 mg·kg^-1 and the text result had exceeded the critical value of Cd hyperaccumulators which was 100 mg·kg^-1. The above ground dry weight and below ground dry weight in A. conyzoides plant decreased gradually with Cd concentration increasing. The above ground dry weight and below ground weight would be inhibited significantly at the moderate Cd concentration stress and high Cd concentration stress. The ratios of root to shoot among different treatments increased gradually with Cd concentration increasing which were higher than the control. It followed that root system growth of A. conyzoides would be inhibited obviously at the high Cd concentration stress. Meanwhile the high Cd concentration stress had a negative impact on nutrient absorption and water uptake of the plant shoot. Ultimately the high Cd concentration stress inhibited the growth and yield increase of plant. With Cd concentration increasing,the maximal photochemical efficiency(Fv/Fm)and potential photochemical efficiency of PS Ⅱ(Fv/Fo)increased gradually,while both the initial fluorescence(Fo)and the maximum fluorescence(Fm)decreased gradually,the quantum yield(ФPS Ⅱ),electron transfer efficiency(ETR),the photochemical quenching coefficient(qP)and non photochemical quenching coefficient(qN)increased firstly and then decreased. It was thus clear that,Cd stress disrupted photosynthetic characteristics of A. conyzoides leaves in normal times and delayed senescence in plants. But fluorescence induction kinetic parameters among different treatments had no significant differences. Cd stress had less impact on electron transport,photochemical reactions and heat dissipation ability in the leaves of A. conyzoides. In the research,the growth and dry weight would be inhibited obviously at the high Cd concentrations stress,however,the above ground Cd content and below ground Cd content in A. conyzoides plant has had strong Cd accumulation capacity. Consequently,A. conyzoides could be served as an alternative plant for the phytoremediation which could be used to help repairng Cd contaminated soil.