Production of SH compounds in higher plants of different tolerance to Cd

Abstract

The roots of six plant species, in three families, were exposed to 0, 3 and 9 μM CdCl₂ for three days. The tops and roots were analyzed for total Cd. The roots were extracted with tris buffer at pH 7.2 and the extracts were analyzed for Cd and were also extracted with HAc-EDTA buffer and the extracts were analyzed for Cd, glutathione and SH compounds other than glutathione (SH-G). After exposure to Cd, the concentration of SH-G was highest in cucurbits, medium in grasses and lowest in legumes. Cd extracted from the roots at pH 7.2 increased with Cd treatment and correlated with SH-G in all families. This suggests that the Cd incorporated into the cells was detoxified by SH compounds produced in proportion to the degree of Cd incorporation. This may be one mechanism for tolerance in plants which accumulate Cd.

The percentages of Cd transported from roots to tops were highest in cucurbits and lower in grasses and legumes. Cd incorporated into the root cells (symplast), was transported to top through apoplast.