Protective effect of silicon on phenolic biosynthesis and ultraviolet spectral stress in rice crop

A work of ultraviolet microspectrometry and immuno light microscopy of cinnamyl alcohol hydrogenase (CAD) in the cells of leaf blades was carried out on rice plants grown in a paddy field with (+Si) or without (-Si) application of a silicate fertilizer. The pattern of silicon distribution on the longitudinal surface of leaf blades by X-ray microanalyzer, morphological characteristics, and gross composition such as silica, other major mineral elements, cellulose, non-cellulosic polysaccharides, lignin and phenolic acids were also compared between both rice plants. The X-ray microanalysis of silicon indicated the higher deposit on dumbbell bodies and other surface area in the +Si rice plants compared with those of the -Si rice plants. The +Si rice plants also showed the lower immuno-reaction of antiserum of the CAD in the cell walls of sclerenchyma, vascular bundle sheath and metaxylem vessel cells. The +Si rice plants had the lower UV absorbance around 280 and 320 nm in the leaf blades compared with those of the -Si rice plants. Microscopic observations of leaf blades in both sets of rice plants were also consistent with results of phenolic acids examined. This study suggests that silica fertilization and/or silicate accumulation in the leaves can be associated with decreases of the phenolic biosynthesis in rice plants. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.