铝胁迫下水稻幼苗根尖表面pH和有机酸的动态变化

Dynamic change in surface pH and organic acid content in rice seedling root-tip exposed to aluminum stress

采用添加pH指示剂溴甲酚紫的琼脂糖凝胶平板技术,检测了铝胁迫下水稻幼苗根尖表面pH和根尖细胞有机酸含量的动态变化。铝胁迫下,幼苗根尖表面颜色在处理第1h、3h、6h无明显变化;而对照处理第1h时水稻幼苗根尖表面颜色已发生明显变化,呈浅橙色,处理第3～6h幼苗根尖表面变为橙红色。表明在正常条件(pH4.4)下水稻幼苗根尖表面pH有碱化趋势,铝胁迫条件下(pH4.4)水稻幼苗根尖表面pH碱化的趋势被抑制。在测定的铝胁迫水稻幼苗根尖细胞细胞质10种有机酸中,发现3种有机酸含量的变化趋势不同。草酸含量无明显变化;柠檬酸含量在铝处理0～3h内变化不明显,处理3h后迅速提高,处理12h达最大值后转而下降,铝胁迫24h时柠檬酸含量比胁迫12h时降低16.27%,差异达显著水平,胁迫24h后的柠檬酸含量变化不大但仍高于胁迫6h的柠檬酸含量;铝处理3h后苹果酸含量较胁迫前下降幅度不大,差异不显著(P>0.05),3h后显著下降,6h后下降趋势不明显。

Surface pH and cytoplasm organic acid contents of root-tips of rice seedlings under aluminum stress were monitored via a modified agarose gelling plate technique, with bromocresol purple as pH indicator. While no obvious changes are noted in surface color of rice seedling root-tip under Al stress for 1 h, 3 h and 6 h, significant changes occur under no-Al stress, showing little orange in 1 h and deep orange in 3～6 h. Surface pH of Al-free rice seedling root-tip is time-dependent and strongly alkaline under an initial pH of 4.4 condition. On the contrary, increase in surface pH of rice seedling root-tip is inhibited by Al stress. Under 200 μmol·L-1 Al stress, three out of a total 10 detected organic acids in cell of rice seedling root-tip, show varying, time-dependent dynamics. There is insignificant change in oxalic acid in rice seedling root-tip during the test and a minimal change in citric acid in the initial 3 h of Al stress. However, citric acid rapidly and significantly increases then, reaching the maximum in 12 h （P0.05） before decreasing by 16.27% in 24 h. Though change in citric acid is small （P〉0.05） after 24 h of Al stress, it is still higher than that in 6 h. Malic acid in rice seedling root-tip decreases, but at an insignificant rate in 3 h of Al stress. After 3 h, malic acid decreases significantly, but the decrease ceases to be significant after 6 h of exposure to Al stress.