The bulk of potentially arable land (30%–40%) in tropical and subtropical regions of the world is acidic, and one of the major menaces particularly evident in acidic soil is the phytotoxicity of aluminum (Al) that limits the growth and productivity of agricultural crops. At neutral pH of the soil, Al resides in stable form, but when the pH of soil drops below 5.5, solubilization of the toxic form of Al occurs, making an organism specifically vulnerable to the precarious effects of the ion. Plants under Al stress incur several incurable toxicity symptoms such as rapid and transient overgeneration of reactive oxygen species ROS O H O OH: , ,2 2 2
• •−( ) that resulted in oxidative burst; further, toxic symptoms involve subsequent reduction in the acquisition of water and mineral uptake by the plant that consequently results in significant reduction of crop yield. Quick and rapid advancement in understanding the tolerance mechanism of Al has been achieved in the last decades because of the intensified research on the specific area of Al biochemistry and molecular biology. Besides the exclusion and detoxification mechanism employed by plants, it has been found after exhaustive research that the macronutrient silicon (Si) also plays a central role in the amelioration of Al toxicity. Substantial progress has been made to develop our understanding of the physiology of Si-induced amelioration of Al toxicity in plants.