Cadmium Tolerance in Plants: Antioxidants, Phytochelatins, Metallothioneins, Nutrient Management and Immune Response

Cadmium (Cd) is a potentially harmful heavy metal and a non-essential trace element that stunts plant development and growth and enters the environment through a broad spectrum of anthropogenic activities. One of the biggest problems in the world is soil pollution, which significantly impacts plant development and soil characteristics. Even though Cd has no biological use in plants, the plants may readily access it. Cadmium can reach the xylem as soon as it enters the roots through an apoplastic and symplastic route. Plants have distinct patterns of metal accumulation and dispersion in various plant sections. Once within the cells, Cd can interfere with various physiological and metabolic functions in plants. Cadmium suppresses seed germination, slows seedling development, and lowers plant biomass even at low levels of exposure. It results in electrolyte leakage and alters photosynthesis, transpiration rate, stomatal conductance and relative water content. Reactive oxygen species (ROS) cause chromosomal abnormalities, DNA damage, and gene mutations that impact the cell division and cell cycle that are triggered by Cd. Plants have responded by evolving many coping mechanisms to reduce and overcome the harmful effects of Cd. Moreover, soil microbes contribute importantly to plants’ Cd tolerance by enhancing plants’ physiological and morphological characteristics and lowering metal phytoavailability. In the present chapter, we will discuss the tolerance of Cd toxicity in plants.