Genetics Of Tolerance In Agronomic Plants*

Abstract

Mineral elements exist as cations and anions under biological conditions, and inside biological systems metal cations form complexes with various forms of ligands. Many of these cation complexes are biologically active, such as metals in enzymes and other functional proteins.1 The amount of metal available to plants is determined by the soil composition and its physical and chemical properties. Major soil types are characterized by nutrient composition and, in many cases, by their potential for causing specific metal stresses. Metal excesses or deficiencies, occurring throughout the world, are among the most important factors limiting crop production. Approximately 25% of the world soils are considered to induce some kind of metal stress in plants.2-4 The status of a metal in the plant depends upon the concentrations of other elements in the soil and upon the plant genotype response.5 Consequently, the effect of a metal is an interaction between concentration, availability, and the plant genotype. Natural evolution of floras on different soils have led to the development of plant species and ecotypes adapted to particular soil conditions of which the soil metal content is a critical factor. The evolutionary adaptations of plant species to metaliferous soils have given rise to the concept of geobotanical indicators.