Toward understanding the influence of soil metals and sulfate content on plant thiols

Plants respond to increased concentrations of metals by a number of mechanisms, including chelation with phytochelatins (PCs). Soil specimens and plants (Veronica anagalis-aquatica, Typha domingensis, Cynodon dactylon, Chenopodium album, Rumex dentatus, Amaranthus gracilis, Chenopodium murale, Inula viscosa) leaves were collected from two sites in northern Jordan and subsequently metals (cadmium, copper, and lead), sulfate, and PC (from leaves) levels were determined. One of these sites was contaminated with metals and the other served as a control site. The contaminated site had elevated cadmium, copper, lead, and sulfate levels. This increase of metal and sulfate levels in the soil at the contaminated site correlated with a rise in plant total glutathione (GSH(T)) and cysteine (CYS(T)). These increases were not attributed to an elevation in total phytochelatin levels. However, a significant increase in the ratio of short-chain phytochelatins to the total phytochelatin stores was observed. The individual effects of metals and sulfate on glutathione, short-chain PCs and long-chain PCs levels were dissimilar.