微电极法测定水稻叶片液泡中硝酸根离子的再调动

 作物液泡中硝酸根离子的再调动和再利用与作物氮素高效利用关系密切。利用硝酸根离子微电极技术测定了在外界继续供应和停止供应硝态氮后，不同水稻品种叶片细胞质和液泡中硝酸根离子活度在24 h内的变化情况。结果表明：(1)在继续供应硝态氮后，水稻植株组织水平的硝酸根离子浓度没有显著的变化，而停止供应硝态氮的植株体内硝酸根离子浓度却有随缺氮时间延长而降低的趋势；(2)水稻叶片细胞质和液泡中硝酸根离子活度存在着明显不同的变化趋势。在停止供应硝态氮的24 h内，水稻叶片液泡中的硝酸根离子浓度逐渐降低，而细胞质中的硝酸根离子却维持在一个较低的浓度且基本稳定；(3)扬稻6号液泡中和细胞质中的硝酸根离子活度均高于农垦57，且在停止供应硝态氮的不同时间段，液泡中硝酸根离子的释放速率也均高于农垦57。上述结果表明在受到硝态氮营养胁迫时，水稻先前积累在叶片液泡中的硝酸根离子可以在细胞中进行重新的利用和分配，而且籼稻品种扬稻6号对液泡硝酸根离子再调动能力显然高于粳稻农垦57。

Remobilization of Nitrate in Rice Leaf Vacuoles Measured with Double-Barrelled Nitrate-Selective Microelectrodes

Remobilization of nitrate in leaf vacuoles of crops is closely related to nitrogen use efficiency of crop. Double-barrelled nitrate selective microelectrodes were used to measure the nitrate activity in leaf cytosol and leaf vacuoles of different rice cultivars in either nitrate supply or deprivation conditions. The results obtained are listed as follows. (1) The nitrate concentration in tissue of rice plants showed no significant changes during the period of nitrate supply, but it decreased gradually after deprivation of nitrate. (2) Different situations emerged in individual leaf cells where nitrate activity of vacuoles decreased significantly while the nitrate activity of cytosol was almost unchanged when nitrate was removed. (3) Nitrate activities in cytosol and in vacuoles in leaves of Yangdao6 were higher than those of Nongken57, moreover, nitrate released from the leaf vacuole of Yangdao 6 at different times of nitrate deprivation was faster than Nongken57. It is concluded that nitrate stored in leaf vacuoles serves as a buffer for nitrogen utilization in cytosol and thus can increase the nitrogen use efficiency in plant itself.