Chapter 11 - Brassinosteroids in plant nutrition and heavy metal tolerance

Abstract

The rapid increase in industries and anthropogenic activities is causing serious threats in terms of environmental pollution with heavy metals. The ecosystem is destructed by the incorporation of these metals in the food chain. Due to the nondecaying nature of heavy metals, soil contamination with heavy metals has appeared as a major ecological obstacle all over the globe. The usage of plant growth regulators has overturned the metal-induced impacts on plant growth. Among these hormones, brassinosteroids (BRs) play a key part in enhancing plant performance and resistance to different environmental stresses like various microorganisms attack, drought, salinity, extreme temperature conditions, and metal toxicity by improving productivity, photosynthesis, consolidating antioxidant defense system and detoxification ability, and also via modulating the functioning of stress-associated genes. Notably, BRs and associated signaling elements have been found to be involved in intricate cross-talk with nutritional components as well as toxic heavy metals in the soil microenvironment. The stimulating properties of BRs under heavy metal stress on the physicochemical characteristics of plant development are seen through enhancement in morphological aspects like germination, shoot and root length, yield, and biomass. Plants treated with BRs under heavy metal stress trigger their antioxidant defense system and reduce the level of the harmful elements in them which may be attributed to the fact that BRs stimulate the permeability of the cell membrane and have an affinity to the membrane-bound proteins. BRs also prevent reactive oxygen species (ROS)–induced lipid damage resulting from metal stress and enhance the activity of antioxidative enzymes to scavenge ROS. Overall, metal-induced toxicity is alleviated in plants when BRs are applied in specific amounts.