| There are many genotypic differences in response of rice plant to deficient Phosphorus (P), screening and breeding P efficiency rice genotypes would be one of effective alternatives to alleviate P deficiency and to increase the utilization efficiency of P fertilizer. Understanding the nutritional and physiological mechanisms of rice plant adaptation to low P stress would be very helpful to the above program of screening or breeding. In the present, based on the materials screened from the preliminary study, a solution culture experiment was conducted to evaluate the discrepancy of the root activity, rhizosphere acidification and excretive carbohydrate in different genotypic at low P stress. We also analyze the effect on the biomass. In addition, with the materials of rice with high P uptake efficiency genotypes, we study the differentially express of rice root proteins under the condition of low P stress. The results obtained were summarized as follows:1．The effect of the root activity, rhizosphere acidification and excretive carbohydrate in different P efficiencies rice at low P stress.Under the condition of low P stress, both the biomass of the IR71331 (high P-absorption efficiency) and IR20 (low P-absorption efficiency) dropped. And the Shoot was affected more seriously than root, but the root/shoot ratio in IR71331 increased more. The pH of the solution dropped with tow rice genotypes. It fell slowly in the first time of low P stress, then became quickly, reaching the least at 96 hours and it dropped by 1．69 in the IR71331．From the analysis of the root system activity, the ability of root system oxidation dropped at the low P stress, but it dropped less by 43．8% in IR71331 compared to the control than in IR20．From the quantitative analysis of total exudation carbohydrate, the IR71331 dropped less compared to the control, but the ratio of organic carbohydrate increased, showing the IR71331 had better resistance to low P stress.The Rice with high P uptake efficiency had the better ability of absorption was relevant to its ability of root system oxidation and high acidification.2．The differentially expressed of root proteins in rice with high P uptake efficiency genotypeTotal proteins were extracted from the root that were obtained respectively at low P stress of IR713313 after 3 days and 6 days, and were separated by two-dimensional gel electrophoresis (2-DE). It was found that 29 proteins expressed differentially in the different treatment time courses significantly. Ten of them were identified by MALDI-TOF/MS and database searching. According to their function, they were divided into four categories: signal transduction, expression of gene, metabolism and ion transport. These proteins involved in many resistant physiological reactions, including the recognition of signal, the cleavage of RNA, the transduction of signal, the regulation of signal, the degradation of protein, the transportation and balance of ion.The Serine protease inhibitor and the MYB transcription factor-like protein, which might be related closely to the response to the low P stress, were found in this research. They would be confirmed and studied in the ongoing research work. Basing on the result, we would adopt functional cloning strategy to isolate and clone the key genes response to the low P stress.
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