Abstract: A sand culture experiment and a hydroponic culture experiment were conducted to study genotypic variation of rice in utilization of sparingly soluble phosphates (Al-P and Fe-P) and its relationship with mobilization characteristic of root exudation. Both Al-P and Fe-P treatments significantly decreased the plant biomass, total P uptake, and plant total P concentration of eight rice genotypes in comparison with the P-sufficient treatment. There were genotypic variations in plant biomass, P uptake, and plant P concentration under Al-P or Fe-P treatments. Root exudation of either the P-sufficient plants or P-deficient plants had certain ability to mobilize P from sparingly soluble phosphate. The root exudation of P-deficient plants showed higher ability to mobilize P from Al-P or Fe-P than that of P-sufficient plants. Correlation analysis showed that P mobilization from Al-P or Fe-P by root exudation of P-deficient plants did not correlate with total P uptake from Al-P or Fe-P by rice, suggesting that genotypic variation in P mobilization from sparingly soluble phosphate by rice root exudation could not account for the genotypic variation in P uptake from sparingly soluble phosphate. Low P treatment increased secretion of malic acid and oxalic acid for most of the eight genotypes. However, the amount of malic acid and oxalic acid secretion in the root exudation was not consistent with P mobilized from sparingly soluble phosphate by root exudation.

Key words: rice, root exudation, mobilization, organic acid, sparingly soluble phosphate, genotypic variation

摘要： 通过砂培和溶液培养试验，研究了水稻利用难溶性磷酸盐（AlP和FeP）的基因型差异及其与根系分泌物活化特性的关系。 与正常供磷处理相比，AlP和FeP处理都显著降低了8个水稻基因型的生物量、吸磷量和植株磷浓度。在AlP或FeP处理下，8个水稻基因型的生物量、吸磷量和植株磷浓度都存在显著的基因型差异。正常供磷处理和低磷处理的水稻植株的根系分泌物对难溶性磷酸盐都具有一定的活化能力。相对而言，磷缺乏植株的根系分泌物对AlP或FeP的活化能力都要高于正常供磷处理的植株。相关性分析表明，磷缺乏植株根系分泌物对AlP或FeP的活化能力和水稻吸收AlP或FeP的能力之间没有显著的相关性，这说明根系分泌物对难溶性磷酸盐的活化能力并不能反映水稻吸收难溶性磷酸盐的能力。对于大部分基因型来说，低磷处理增加了根系苹果酸和草酸的分泌量。然而，根系有机酸的分泌量与根系分泌物对难溶性磷酸盐的活化能力并没有呈现一致的结果。

关键词: 水稻, 根系分泌物, 活化, 有机酸, 难溶性磷酸盐