Impact of Heavy Metals on Photosynthesis

Abstract

Use of phytotoxicity of metallic compounds dates back to 1896, when the French farmers applied Bordeaux mixture (copper sulphate, lime and water) to control fungal pests (Martin and Woodcock 1983). Currently, global heavy metal (HM) pollution is a serious environmental concern. Photosynthetic functions have been invariably affected either directly or indirectly by HMs (Baszyński and Tukendorf 1984; Clijsters and Van Assche 1985; Baszytńiski 1986; Sheoran et al. 1990; Greger and Ögren 1991; Krupa and Baszyński 1985, 1995; Prasad 1995a, 1997). A critical examination of the literature reveals that HMs react with the photosynthetic apparatus at various levels of organization and architecture i.e. accumulation of metals in leaf (main photosynthetic organ); partitioning in leaf tissues like stomata, mesophyll and bundle sheath; metal interaction with cytosolic enzymes and organics; alteration of the functions of chloroplast membranes; supramolecular level action, particularly on PS II, PS I, membrane acyl lipids, and carrier proteins in vascular tissues; molecular level interactions, particularly with photosynthetic carbon reduction cycle enzymes, xanthophyll cycle and adenylates.