Aluminum Stress On Initial Roots Of Sugarcane And The Alleviating Effect By Ca,B,Mg

Phytotoxicity of aluminum(Al) is widely considered to be a serious agricultural problem limiting crop productivity in acidic soils. The primary site of Al toxicity locates in root apices. In this study, the ability of Al-tolerance of eight sugarcane cultivars was identified by root elongation measuring and hematoxylin staining, and the effect of Al on root growth of GT15 as well as some alleviating effect by applying Ca, B, Mg were deeply investigated. The results showed that different sugarcane cultivars differed in tolerance to Al stress, when TT24 and GT15 were Al-tolerant and Al-sensitive cultivars respectively. In the presence of 20mol.L-1 Al, elongation of initial roots of GT15 was severely inhibited. The stress of Al also resulted in curvature of root tips, and decreased the secretion of mucilage. In addition, Al stress promoted the activity of POD and SOD in root tip (6,12, 24h). Al was mainly accumulated in 0-10mm-segment of root tips. This region plus epidermis of the root tips were intensively stained by hematoxylin. But the stress induced by Al could be alleviated effectively by Ca. Under this circumstance, elongation of initial roots was only repressed slightly, whereas the alleviating effect of B and Mg(1.0 mmol.L-1) was not significant. The organic acids secreted by roots were also determined in this study. In contrast to the absence of Al, roots secreted more tartaric acid when the roots exposed to 20mol.L-1 Al.