中文摘要：

以红树植物白骨壤为实验材料,通过水培实验,施加不同浓度的Si和Cd,对比研究Cd胁迫下外源Si对白骨壤幼苗低分子质量有机酸代谢的影响,以探讨外源Si对红树植物抗重金属的影响效应和作用机理.结果表明：Cd胁迫显著降低白骨壤幼苗各器官和根系分泌物中低分子质量有机酸含量;Si对有机酸代谢的影响随Cd处理水平不同而不同,在对照（Cd 0 mg/L）和低质量浓度（Cd 0.5 mg/L）处理下,Si对各器官有机酸含量影响不显著或降低其含量,高质量浓度Cd（Cd 5 mg/L）处理下,Si显著增加叶片和茎部有机酸总量,显著增加根系分泌物中柠檬酸含量;白骨壤各器官和根系分泌物有机酸含量两两间显著相关.由此推测Si是白骨壤生长的有益元素,Si缺乏造成的营养胁迫促使植物体内有机酸代谢做出响应;Si促进高质量浓度Cd处理下植物体内的有机酸代谢,对缓解白骨壤Cd毒害效应具有重要意义.

英文摘要：

Mangrove plants seem to be highly tolerant of high levels of heavy metal pollution.Some researchers have focused on the mechanisms involved in their metal uptake and tolerance.However the important mechanisms involved are still only partially understood.There are higher concentrations of available Si in mangrove sediments.There is increasing evidence that Si has many beneficial effects on mangrove growth and development and can improve heavy metal resistance of mangrove.In order to explore the Si alleviation mechanisms of the toxicity of heavy metal on mangrove,we investigated the effects of Si and Cd on low molecular weight organic acid metabolism of Avicennia marina by pot experiment.The concentration of low molecular weight organic acid in different organs and root exudates were decreased by Cd addition.The effect of Si on low molecular weight organic acid metabolism varied with Cd treatments.Si did not affect or decreased the concentrations of low molecular weight organic acid in different organs and root exudates in 0 mg/L and 0.5 mg/L Cd treatments.Si increased the total concentrations of low molecular weight organic acid in the stem and leaf and the concentration of citric acid in root exudates under 5 mg/L Cd treatments.The correlation analysis showed that there was a significantly positive correlation between the total concentration of low molecular weight organic acid in different organs and root exudates of A.marina.This suggested that Si was beneficial for the healthy growth and development of A.marina and organic acid metabolism was enhanced by the lack of Si nutrition stress.Si enhanced low molecular weight organic acid metabolism of A.marina under high Cd stress,which may be related to the amelioration by Si of Cd toxicity.