Chapter 2 Silicon as a beneficial element for crop plants

Silicon (Si) has not been proven to be an essential element for higher plants, but its beneficial effects on growth have been reported in a wide variety of crops, including rice, wheat, barley, and cucumber. Si fertilizer is applied to crops in several countries for increased productivity and sustainable production. Plants take up Si in the form of silicic acid, which is transported to the shoot, and after loss of water, it is polymerized as silica gel on the surface of leaves and stems. Evidence is lacking concerning the physiological role of Si in plant metabolism. Since the beneficial effects of this element are apt to be observed in plants which accumulate Si, the silica gel deposited on the plant surface is thought to contribute to the beneficial effects of Si, which may be small under optimized growth conditions, but become obvious under stress conditions. In this review, the effects of Si under biotic stresses (disease and insect damage) and abiotic stresses including climate stresses (typhoon and cool summer damage), water deficiency stress, and mineral stresses (deficiency of P and excess of P, Na, Mn, N and Al) are discussed.