Functions and toxicity of cadmium in plants: recent advances and future prospects

Heavy metals are important environmental pollutants and their toxicity is a problem of increasing significance for ecological, evolutionary, nutritional, and environmental reasons. Of all non-essential heavy metals, cadmium (Cd) is perhaps the metal that has attracted the most attention in soil science and plant nutrition due to its potential toxicity to humans, and also its relative mobility in the soil plant system. This review emphasises Cd toxicity on plants with regards to ecological, physiological, and biochemical aspects. It summarises the toxic symptoms of Cd in plants (i.e. growth and plant development, alterations in photosynthesis, stomatal regulation, enzymatic activities, water relation, mineral uptake, protein metabolism, membrane functioning, etc.). The main barriers against Cd entrance to the cell, as well as some aspects related to phytochelatine-base sequestration and compartmentalisation processes, are also reviewed. Cd-induced oxidative stress is also considered one of the most widely studied topic in this review. This review may help in interdisciplinary studies to assess the ecological significance of Cd stress.