不同镉积累型苋菜（Amaranthus mangostanus L.）根际低分子量有机酸与镉吸收的关系

 【目的】研究低镉积累型苋菜紫背苋和高镉积累型苋菜天星米在镉胁迫下低分子量有机酸分泌特征及其与苋菜镉生物积累的关系。【方法】采用溶液培养法进行试验。【结果】随供镉浓度增加，紫背苋根、茎和叶生物量显著降低，而天星米生物量未发生明显改变。不同镉暴露条件下，苋菜分泌的有机酸总量表现为天星米远高于紫背苋，有机酸含量均表现为柠檬酸>苹果酸>乙酸>丙酸>丁酸，且以柠檬酸和苹果酸为主。两品种各有机酸数量占有机酸总量的比例基本一致。随供镉浓度增加，两个苋菜品种根分泌的各有机酸量增加，各有机酸分泌量的增幅均表现为天星米大大高于紫背苋，植株根、茎和叶镉含量与积累量也相应表现为天星米大大高于紫背苋。【结论】苋菜镉的生物积累与有机酸种类没有特异性关系，但与有机酸的总量有关。镉胁迫诱导根系分泌有机酸的数量，在引起两品种对镉吸收的差异方面起重要作用。

Low Molecular Weight Organic Acids in Rhizosphere and Their Effects on Cadmium Accumulation in Two Cultivars of Amaranth(Amaranthus mangostanus L.)

【Objective】 To examine whether low- molecular weight organic acids (LMWOAs) in root exudates of amaranth play a role in Cd hyperaccumulation, we compared the amounts and composition of LMWOAs collected from two cultivars of amaranth，Zibeixian ，a low Cd accumulator，and Tianxingmi，a high Cd accumulator. 【Method】 Plants were grown hydroponically and three treatment (Cd 0、1 and 2.5 mg/L ) were later imposed for 1 wk before collection of LMWOAs. 【Result】 With the increase of solution Cd concentration, the biomass and its components of Zibeixian decreased dramatically, while those of Tianxingmi remained stable. In all treatment, total amount of LMWOAs in rhizosphere of Tianxingmi were significantly higher than that in Zibeixian，and the content of LMWOAs in two cultivars followed the same tendency, i.e. citric>malic>acetic>propinonic>butyric, and citric acid and malic acid predominated the composition of LMWOAs. The percent distribution of total LMWOAs of Zibeixian was very similar to Tianxingmi. With the increase of solution Cd supply, the content of LMWOAs in rhizosphere increased dramatically for both two cultivars, and the increment of LMWOAs of Tianxingmi was found to be greatly higher than that of Zibeixian. 【Conclusion】Therefore, Cd accumulation in amaranth was highly related to the total amount of LMWOAs in rhizosphere，and the differential increment of LMWOAs in the rhizosphere induced by Cd exposure may played an important role for Cd bioaccumulation by the high and low Cd accumulating cultivars of amaranth.