Studies on the heavy-metal tolerance and interactions between several metal-binding ligands in plants exposed to complex pollution conditions.

在本研究中，我们研究了植物在复杂条件下的重金属耐受性和与金属结合配体的相互作用的可能机制。结果表明：（1）植物螯合素（PC）的形成和积累参与了番茄细胞耐重金属特性的表达。对于解毒机制，所需的PC-复合物的形成可以强烈促进与镉，但抑制其他元素，如铜，砷和B，这是不纳入前PC-镉复合物。(2)文献报道镉和砷的转运与巯基肽如PC和GSH有关。然而，有机酸和一些无机物如硼酸盐会显著影响它们的运输。在不同金属离子和阴离子混合的条件下，它们从根向地上部的转运速率有很大差异（如Cd和Zn比Cu或As快得多，但其转运方式与某些有机配体有关），硼酸盐促进Cd向地上部的转运，而抑制As向地上部的转运。(3)其他主要的一价和/或二价金属离子在植物体内与配体的转运和再分配也有其独特的机制，这为今后的研究提供了新的前景。

In the present studies, we examined the possible mechanisms for the heavy-metal tolerance and interactions with metal-binding ligands in plants exposed to complex conditions. We found(1) In tomato cells, phytochelatin (PC) formation and accumulation are involved in the expression of the heavy-metal tolerance characteristics. For the detoxification mechanism, required formation of the PC-complex can be strongly facilitated with Cd but inhibited by other elements such as Cu,As and B, which are not incorporated in the former PC-Cd complex.(2) Transports of Cd and As have been associated with the thiol peptides such as PCs and GSH in literatures. However, their transports can be significantly affected by organic acids and some inorganic such as borate. Under conditions where different metals and anions are mixed in medium, their transport rates from roots to shoots are very different (e.g. Cd and Zn are much faster than Cu or As, but in a manner which is correlated with some organic ligands).Here, borate facilitates the Cd transport but inhibits As transport to shoot.(3) Other major mono- and/or divalent metal ions reveal other unique mechanisms for transport and redistribution with ligands in plants, which taken together present new prospects in futurestudy.