铅污染土壤中杂草对铅的吸收

利用盆栽试验，研究了杂草对铅的吸收积累及铅污染土壤中杂草养分吸收和根系丛枝菌根真菌(AMF)侵染的特点．结果表明，铅污染对杂草生长没有明显影响．铅主要富集在根系中，对某些杂草吸收养分有影响．苗期除了升马唐钾含量铅处理与对照之间有显著差异外，其它差异均不显著，说明苗期铅处理对鸡眼草、苦荬菜、升马唐和无芒稗吸收养分基本没有影响；成熟期铅处理中苦荬菜和升马唐的全磷含量极显著高于对照，而无芒稗全氮含量显著低于对照．根系AMF的侵染特点是，无论是苗期还是成熟期。鸡眼草和升马唐根系的AMF侵染率变化不大；苦荬菜铅处理低于对照，苗期铅处理和对照的根系侵染率分别是45．52％和69．44％，成熟期分别是74．64％和82．21％；无芒稗铅处理根系的AMF侵染率显著高于对照，苗期铅处理和对照的根系侵染率分别是82．45％和59．19％，成熟期分别是91．36％和78．28％．

Lead absorption by weeds from lead-polluted soil

A pot experiment with red soil was installed in 2002 and 2003 to study the impact of lead pollution on weed growth,its lead and nutrients uptake,and AMF colonization.The results showed that lead pollution had no significant influence on weed growth,and the absorbed lead was mainly accumulated in root system.The impact of lead pollution on nutrients uptake by weeds was depended on weed species,their growth stages,and kinds of nutrients.No significant difference was found between lead treatment and control in nutrient contents except potassium in Digitaria adscendens at its early growth stages,and lead had little influence on the absorption of nutrients by Kummerowia striata,Ixeris chinensis,Digitaria adscendens and Echinochloa crusgalli var. mitis.The phosphorus content in Ixeris chinensis and Digitaria adscendens at their ripen stage sampled from lead-polluted soil was significantly higher than that from control,while the nitrogen content in matured Echinochloa crusgalli var. mitis sampled from polluted soil was significantly lower than that from the control.There existed great difference of mycorrhizal colonization among various weed species.The infection rate of Kummerowia striata and Digitaria adscendens showed a slight difference between lead treatment and control both at vegetative and ripen stage.Lead pollution hindered the colonization of Ixeris chinensis.In lead-polluted soil,the AMF infection rate of Ixeris chinensis was 45.52% at vegetative stage and 74.64% at ripen stage,while in the control,it was 69.44% at vegetative stage and 82.21% at ripen stage.Echinochloa crusgalli var. mitis,an annual weed,showed an opposite response of AMF colonization to lead pollution.The colonization rate of AMF in Echinochloa crusgalli var. mitis root was higher under lead pollution condition,being 82.45% at vegetative stage and 91.36% at ripen stage,while in the control,it was 59.19% and 78^28%,respectively.