Heavy Metal Interactions with Plant Nutrients

Abstract

I.INTRODUCTION According to the classical deftnition "Interactions between nutrients occur when the supply of one nutrient affects the absorption, distribution or function of another nutrient. Thus, depending on nutrient supply, interactions between nutrients can either induce deficiencies or toxicities and can modifY growth response" (Robson and Pitman, 1983). There are many nonspeciftc as well as speciftc interactions between mineral nutrients of plants (Robson and Pitman, 1983; Marschner 1988). When contents of any mineral nutrients are near the deftciency range the importance of interactions between two mineral nutrients increases. Speciftc interactions, e.g. competition between nutrients at the cellular level or replacement of one nutrient by another, are also important in evaluating critical toxicity contents (Foy et aI., 1978; Marschner, 1988). Competitive interactions can also occur between essential nutrients and other elements in the environment, particularly with heavy metals. Heavy metals, aggressive and ufortunately still very common environmental pollutants, are easily taken up by plants and easily compete with many nutrient elements. These phenomena suggest that more attention should be paid to the relationships between heavy metals and other essential plant nutrients. 2. HEAVY METALS UPTAKE AND DISTRIBUTION From the physiological point of view we divide heavy metals into two groups (Siedlecka, 1995):-metals necessary for plant metabolism as enzyme activators or regulators, e.g. Fe, Cu, Mn, Mo, which may become toxic if supplied in excess; 287