两种生态型东南景天根系分泌物的差异性

Differences of root exudates between two ecotypes of Sedum alfredii Hance

东南景天(Sedum alfredii Hance)具有很强的耐高Zn胁迫、吸收和运输Zn的能力,但其根系如何通过分泌作用实现对Zn胁迫的适应和对土壤难溶性Zn的活化作用,还缺乏机理方面的解释。因此,本研究运用离子色谱、氨基酸自动分析等技术较系统地研究了两种生态型东南景天根系分泌物组成的差异性及其对土壤中不同化合物Zn的活化效应,旨在探明根系分泌物与东南景天超积累Zn的关系。结果表明,两种东南景天的根系分泌物均能够活化土壤中难溶态的ZnO、ZnCO3和Zn3(PO4)2,而对ZnS没有明显地活化作用。通过对根系分泌物组成成分分析,两种生态型东南景天根系分泌物中可溶性糖占绝对优势,有机酸和氨基酸含量很低,且均以非超积累生态型>超积累生态型。超积累生态型东南景天根系分泌物中的可溶性总糖、有机酸(苹果酸除外)、氨基酸等各成分含量均以Zn1.0μmol·L-1处理>Zn500μmol·L-1处理,非超积累生态型东南景天根系分泌物中糖和有机酸含量也随着Zn浓度的增加而减少,而绝大多数氨基酸含量则随着Zn浓度的增加而增加。这说明本试验条件下测定的根系分泌物组分在东南景天超积累Zn过程中并不起主导作用。

Sedum alfredii Hance has been defined as a new Zn/Cd hyperaccumulating plant species native to China, and has an exceptional ability to tolerate and hyperaccumulate Zn and Cd. However, little is known about its root physiological responses when it is exposed to high Zn concentration. In this study, solution culture experiment and zinc mobilization test were carried out to characterize root exudates of Sedum alfredii Hance and their effects on soil Zn mobilization. Results indicated that root exudates of the two ecotypes of Sedum alfredii Hance could mobilize the non-labile ZnO, ZnCO3 and Zn3（PO4）2, but could not mobilize ZnS in soils. Soluble sugar was the predominant components of root exudates for the two ecotypes of Sedum a^edii Hance by analysis of their components, while the contents of organic acids and amino acids were very low compared to soluble sugars, and content of the three main kinds of root exudates of the hyperaccumulating ecotype was lower than that of the non- hyperaccumulating ecotype. The content of soluble sugars, organic acids and amino acids in root exudates of the hyperaccumulating ecotype were higher at Zn supply level of 1.0 μmol·L^-1.Lt than at 500 μmol·L^-1 Zn level. The content of soluble sugars and organic acids in root exudates of the non-hyperaccumulating ecotype also decreased at high Zn level, but the content of most amino acids increased with Zn supply level. But it could not be concluded that root exudates detected in the experiment play key role in Zn hyperaccumulating.