【摘要】 以水稻(Oryza sativaL.)品种Azucena(铁耐性)和IR64(铁敏感)为材料,研究了Fe2+毒胁迫下附着于根尖边缘细胞(即原位边缘细胞)的数目、存活率,根尖细胞形态结构、根尖保护酶活性的变化。结果显示,Fe2+毒对根边缘细胞的产生有抑制作用。相对于敏感性品种而言,一定浓度的Fe2+(100~200μmol/L)有利于耐性品种边缘细胞的产生;Fe2+毒对边缘细胞有致死效应,随Fe2+浓度的提升,边缘细胞的存活率呈下降趋势,根尖外围细胞壁增厚,并出现细胞程序性死亡特征(敏感性品种)。同时,Fe2+毒对根尖保护酶活性有一定的影响,2004~00μmol/L Fe2+处理下,耐性品种过氧化物酶(POD)、过氧化氢酶(CAT)、超氧化物岐化酶(SOD)活性都超过对照;敏感品种只有SOD活性超过对照。说明Fe2+毒胁迫下,水稻根尖可通过增加边缘细胞数目、提高细胞拒铁作用,维持较高水平的POD、CAT和SOD活性来对抗Fe2+毒,缓解铁毒害。更多还原

【Abstract】 Toxicity of Fe2+ is one of the major constraints for lowland rice production in tropical and subtropical areas.However the mechanism of Fe-induced inhibition of root growth and the reasons for the spatial variations in Fe2+ sensitivity among the apical root zones are still poorly understood.The root tip is a primary site of Fe2+ toxicity in rice.The root border cells(BC),which originate from the root cap meristem by mitosis,can separately carry out metabolism and resist adverse stress through a series of distinct responses.In this study, the response mechanism of the root tip cells to Fe2+ toxicity were tested by comparing response of rice varieties Azucena(Fe-tolerance) and IR64(Fe-sensitive) known to vary in Fe2+ resistance at a whole-root level.Results showed that Fe2+ toxicity inhibited the development of BC.However,compared to IR64,Fe2+ at 100-200 μmol/L was propitious to the development of BC in Azucena.With increase of Fe2+ concentration,the viability of the rice BC became lower,the cell wall of root tip outermost cells became thicker,and some characteristics of programmed cell death were observed in the cells(Fe-sensitive variety).Meanwhile,Fe2+ concentration affected the activities of peroxidase(POD),catalase(CAT),and superoxide dismutase(SOD).Higher enzyme activities were found in Fe-tolerance variety under high concentration Fe2+(≥200 μmol/L) compared to control.These results indicated that,under the Fe2+ toxicity,root tip could resist Fe2+ toxicity by increasing BC,thickening cell wall,maintaining high POD,CAT and SOD activities.更多还原