Abstract: A hydroponic experiment was carried out to study the responses of 36 rice cultivars with relatively high nitrogen use efficiency to lowphosphorus at the seedling stage and to explore the differences in physiological mechanism between the lowphosphorus tolerant rice cultivars and the lowphosphorus sensitive ones. Great variation existed in the relative values of root dry weight, shoot dry weight, ratio of root to shoot dry weight and tiller number (coefficient of variation: 16.9%,10.9%,114%,16.3%) in different rice cultivars. In addition, correlation analysis showed their relativity was significant or highly significant. Therefore, these four indexes were employed to evaluate the tolerance to phosphorus deficiency comprehensively. Based on these indexes, three rice cultivars were preliminarily screened out as lowphosphorus tolerant and two rice cultivars as lowphosphorus sensitive, respectively. Comparing with the lowphosphorus sensitive cultivars, the lowphosphorus tolerant ones were characterized by more extensive root system coupled with its higher activity, lower Km and Cmin, but higher Vmax and APase activity. However, the lowphosphorus tolerant cultivars differed in physiological mechanism. The research proved the feasibility for screening double efficient rice cultivars of both nitrogen and phosphorus uses. The screened rice cultivars could be used for identifying genes involved in phosphorus efficiency.

Key words: rice, seedling stage, tolerance to phosphorus deficiency, screening, identification

摘要： 以先前通过田间试验筛选出来的36个氮高效水稻品种为供试材料，在苗期进行了耐低磷筛选，并对获得的3个耐低磷和2个低磷敏感品种响应磷素胁迫的生理机制进行了初步研究。结果表明：1)正常供磷和低磷条件下，所有调查性状的相对值(低磷/正常供磷)中，相对根系干质量、相对地上部干质量、相对根冠比和相对分蘖数均具有较大的品种间变异(变异系数分别为16.9%、10.9%、11.4%、16.3%)。相关分析表明，它们呈显著或极显著正相关。因此，这4个性状可以作为水稻苗期耐低磷筛选的评价指标。2) 在低磷条件下，筛选出的3个耐低磷品种比2个低磷敏感品种的根系生长旺盛且活力强，P吸收动力学参数中Km、Cmin小，而Vmax大，酸性磷酸酶(APase)活性升幅大，磷效率在两者之间也存在显著差异。同时，不同耐低磷品种适应低磷胁迫的调节机制也有所不同。表明筛选氮磷双高效的水稻品种是可行的，同时也为后续基因定位和遗传机制的研究提供了材料和生理学依据。

关键词: 水稻, 苗期, 耐低磷, 筛选, 鉴定