Amelioration of Cadmium Stress in Crop Plants by Nutrient Management: Morphological, Physiological and Biochemical Aspects

Plants are sessile organisms therefore, cannot avoid adverse environmental conditions (such as soil salinity, drought, heat, cold, flooding and heavy metal contamination). These stress factors are a menace for plants, prevent them from reaching their full genetic potential and limit crop productivity worldwide. Soil contamination with heavy metals has become a world wide problem leading to losses in agricultural yield and hazardous health effects as they enter the food chain. Among heavy metals, Cadmium (Cd) is a ubiquitous environmental pollutant and is a non-essential highly toxic metal for plants. It significantly damages general plant metabolism and induces oxidative stress. In response to Cd stress, the cells of Cd-resistant plant species can produce metallothioneins, phytochelatins and stress proteins to detoxify Cd ions. The plant cells can also resort to other defense systems to detoxify Cd ions, e.g., exclusion of Cd through the action of plasma membrane, the immobilization of Cd by cell wall and compartmentalization of Cd to vacuols. It has also been found that mineral nutrient status of plants can play a critical role in increasing plant resistance to environmental stress factors. Among mineral nutrients, sulfur (S) and nitrogen (N) are major macronutrients necessary for the plant life cycle, the two processes the uptake and assimilation of S and N in higher plants are the crucial factors determining plant growth and vigor, crop yield and these nutrients play a particular role in contributing to the survival of crop plants under environmental stress conditions. In this review, we focus on the alterations in morphological, physiological and biochemical characteristics in crop plants under Cd stress. Further, the importance of plant mineral nutrients especially S and N in the amelioration of Cd stress has also been reviewed. _____________________________________________________________________________________________________________