Characteristics And Mechanisms Of Cadmium Uptake And Accumulation In Cadmium Accumulator Oilseed Rape Species

The objectives of the present study were to study the characteristics and potential of Cd uptake and accumulation, the ability of soil Cd activited by root exudates, mechanisms of root Cd uptake and plant detoxicity in different Cd accumulator oilseed rapes in soil, root pad and hydroponic cultures.The results showed that Cd uptake curves of four Cd accumulator oilseed rapes Xikou Huazi,Zhongyou Zal, Zhucang Huazi, Zhongyou 119 and Indian mustard accorded with the characteristics ofCd uptake of accumulator. Shoot Cd distribution pattern showed consistent and significant reductionfrom older leaves to younger ones of Cd accumulator oilseed rapes Xikou Huazi, Zhongyou Zal andIndian mustard. Cd accumulator oilseed rape Xikou Huazi had bigger Cd uptake potential than Indianmustard. Root exudation of Cd accumulator oilseed rape Xikou Huazi under Cd treatment had higheractivation on soil Cd than Indian mustard. A significant depletion of exchangeable Cd was found in therhizosphere soil of Cd accumulator oilseed rape, non-tolerant oilseed rape and Indian mustard. Theconcentrations of carbonate bound and organic bound Cd in the rhizosphere of Cd accumulator oilseedrapes were significantly higher than in the non-rhizosphere soil at soil Cd concentration of 60 mg.kg-1.However, for non-tolerant oilseed rape there were no significant difference in the concentrations of thethese two Cd speciations between the rhizosphere and non-rhizosphere.Three predominant forms of Cdin Cd accumulator oilseed rapes, non-tolerant oilseed rape and Indian mustard were NaCl-extractable,acetic acid-extractable and water-extractable Cd. The concentration of water-extractable Cd in Cdaccumulator oilseed rape Xikou Huazi and Indian mustard was significantly lower than non-tolerantoilseed rape.The significant difference existed in rhizosphere Cd speciations and Cd forms in the plants between Cd accumulator oilseed rapes and non-tolerant oilseed rape. This was the important reason that Cd accumulator oilseed rapes uptake and accumulate Cd.