9 - Biochemical and molecular aspects of heavy metal stress tolerance in plants

Abstract

The unhealthy agro-horticultural practices, urbanization and industrialization, have increased heavy metal stress in the ecosystem, including yield penalty and toxicity to crops. The xenobiotic metals are persistent and recalcitrant. In order to manage the heavy metal stress, the plants pose various salvage pathways to minimize the metal toxicity by sequestration and detoxification of heavy metals through transporter proteins such as ATP-binding cassette (ABC) and metal tolerance protein. Heavy metals affect the cyclin-dependent kinases, thereby affecting the progression of the cell cycle. Reactive oxygen species (ROS) eventually causes cellular damage in plants during heavy metal stress is minimized by the antioxidant mechanism of the cell which involves the activity of superoxide dismutase, catalases, phytochelatin synthase, glutathione S-transferase, proline or alpha-tocopherol, besides organic acids like oxalate, citrate, and malate, which sequester metals into the vacuole. This chapter focuses on the biochemical and molecular events in plants undergoing inorganic stress and the various strategies developed by the plants to ameliorate the metal toxicity.