Mitigation Strategies for Cadmium Toxicity in Rice (Oryza sativa L.)

A Comprehensive Review

Abstract

Cadmium (Cd) is a highly toxic heavy metal and a widespread environmental contaminant in paddy fields, where its accumulation in rice (Oryza sativa L.) poses significant risks to plant health, agricultural productivity, and human consumption. Cadmium toxicity adversely affects various physiological and biochemical processes in rice, including seed germination, root and shoot growth, nutrient homeostasis, photosynthetic efficiency, and grain yield. Additionally, Cd exposure induces oxidative stress by generating reactive oxygen species (ROS), leading to cellular damage and metabolic disruptions. To mitigate Cd toxicity, various agronomic, physiological, and biotechnological strategies have been explored. The application of essential nutrients such as zinc (Zn), iron (Fe), silicon (Si), and lime has been shown to alleviate Cd stress by modulating metal uptake and reducing Cd bioavailability in soils. Organic amendments, including compost and biochar, enhance soil properties and immobilize Cd, thereby limiting its translocation to rice tissues. Furthermore, the exogenous application of phytohormones, osmolytes, and signaling molecules has been demonstrated to improve rice tolerance by enhancing antioxidant defense mechanisms and stress response pathways. Genetic and breeding approaches, such as the development of low Cd-accumulating rice cultivars, offer a promising long-term solution for reducing Cd accumulation in edible plant parts. Additionally, utilizing beneficial rhizosphere microorganisms, including mycorrhizal fungi and plant growth-promoting rhizobacteria (PGPR), can further aid in mitigating Cd toxicity. This review provides a comprehensive synthesis of current mitigation strategies and highlights the need for an integrated approach combining soil amendments, genetic improvements, and sustainable agronomic practices to minimize Cd contamination in rice ecosystems.