Regulation of Photosynthesis Under Metal Stress

Metals, as constituents of chloroplasts, chlorophylls, and metabolic pathways are vital for photosynthesis in plants. However, an excess of essential metals and toxic heavy metals bring adverse changes in carbon dioxide (CO2) exchange, carbon (C) fixation, photosynthetic pigments, leaf size, leaf ultrastructure, phytohormones, gene expression, and enzymes involved in the photosynthetic pathways. Plants have several regulatory mechanisms to protect photosynthesis from metal-induced stress including signaling pathways, transport networks, reactive oxygen species (ROS) scavenging, interconversion of chlorophylls, osmoprotection, and expression of stress genes. However, a plant's coordinated response to metal stress is complex and multifaceted. In this chapter, degradation of photosynthesis machinery under metal stress and key mechanisms to regulate photosynthesis are discussed.