蕹菜不同镉积累品种的根际土壤化学特征

Chemical characteristics of the rhizosphere soil of water spinach cultivars differing in Cd accumulation

采用根箱试验研究蕹菜低Cd品种(QLQ)和高Cd品种(T308)的根际土壤化学特征.结果表明:QLQ根际DTPA-Cd含量显著高于T308(P<0.05).QLQ根际pH、氧化还原电位(Eh)显著高于T308(P<0.05),电导率(EC)的表现相反.QLQ根际有机质和水溶性有机质(DOM)含量均高于T308.在污染土壤上,根际低分子量有机酸的组成与含量均存在品种间差异.T308根际检测到乙酸、丙酸、柠檬酸和延胡索酸,而QLQ根际仅检测到柠檬酸和延胡索酸.QLQ根际低分子量有机酸总量(1.93 nmol·g-1DM)极显著低于T308(15.11 nmol·g-1DM,P<0.01).与T308比较,QLQ表现出明显不同的根际土壤化学特征.推测QLQ低Cd积累的根际化学机理可能在于:较高含量的有机质、较低含量的低分子量有机酸及其特异性组成,以及较低的酸化和还原能力,导致其对土壤Cd的活化能力较低,从而降低植株对Cd的吸收积累.

A rhizobox experiment was conducted to investigate the chemical characteristics of the rhizosphere soils of two water spinach cultivars differing in Cd accumulation, QLQ （ a low-Cd cuhi- var） and T308 （a high-Cd cultivar）. The results showed that the diethylenetriamine pentacetate acid extractable Cd （DTPA-Cd） concentration in the rhizos-phere soil of QLQ was significantly higher than that of T308 （P〈0.05）. pH and Eh in the rhizosphere soil of QLQ were significantly higher than those of T308 （P〈0.05）, while EC was opposite. Contents of organic matter and dis- solved organic matter （DOM） in the rhizosphere soil of QLQ were both higher than those of 3308. In contaminated soil, the composition and concentration of low molecular weight organic acids in the rhizosphere between the two cultivars were both different. Acetic, propionic, citric and fumaric acids were detected in the rhizosphere soil of 3308, and only citric and fumaric acids were detected in that of QLQ. The total concentration of low molecular weight organic acids in the rhizosphere soil of QLQ （1.93 nmol·g^-1DM） was lower than that of T308 （ 15.11 nmol·g^-1）M） （P〈0.01）. Compared with the high-Cd cuhivar （ T308）, the chemical characteristics of the rhizosphere soil of the low-Cd cuhivar （QLQ） were obviously distinct, i. e., the relatively higher content of organic matter, the lower content of low molecular weight organic acids with a specific composition, less acidification of soil, and a lower ability in reduction, correspondingly lowering the mobility of Cd in soil and reducing Cd accumulation by plant.