Abstract:

Four low-P tolerant rice genotypes named 99011, 580, 508 and 99112 were used with two low-P sensitive rice genotypes named 99012 and 99056 as reference, to investigate the genetic differences for growth as influenced by different inorganic phosphorus supply, and availability and uptake ability to three insoluble P named organic P, Al-P and RP, using solution culture and sand quartz culture respectively. The results demonstrated that biomass and root dry weight of rices were reduced by low P, but R/S was affected by both supplied P level and uptake ability of plant to low P. Under the condition of low P, the biomass and root dry weight with different inorganic phosphorus treatments were P> CK+Al-P > CK+RP > CK; root dry weight and root shoot ratio of four low-P tolerant rice genotypes were larger than those of two low-P sensitive rice genotypes; For R/S, 580 and 99011 were CK+RP > CK+Al-P > CK> P, 508, 99112 and 99012 were CK> CK+RP > CK+Al-P > P, but 99056 was CK+Al-P > CK+RP > P> CK. The availability of sparingly soluble phosphates and organic phosphorus absorbed by rice seedlings was OP> Al-P> RP, but different rice cultivars had significant difference in response to three insoluble P compounds. P uptake amount for organic phosphorus was 99011> 508> 580> 99012> 99112> 99056, for Al-P was 580> 99011> 99112> 508> 99056> 99012, and for RP was 580> 99112> 99011> 508> 99012> 99056. Furthermore 508 has highest uptake efficiency to low phosphorus; 580 has highest P utilization efficiency , and absorbed more sparingly soluble phosphorus especially Al-P and RP than others; They are maybe one of the important reasons in 508 and 580 for low-P tolerance in 508 and 580. Low-P tolerant rice genotype 99112, a special material, it has small biomass and achieve high relative grain yield. As for low-P sensitive rice genotype 99056, its utilization efficiency to phosphorus is not low, but it just has small root system, only active and uptake a little sparingly soluble phosphorus, and can not absorb low concentration phosphorus.

Key words: Rice, P efficiency, P sources, Uptake and use, Mechanism of tolerance to low-P stress