Effect of P deficiency stress on soybean root system and its secretion of H+ and organic acid

Different genotypes of soybean nf37 and Jihuang 13 were selected as materials,their acidification around the root system(the content of H+ and secretion of organic acids in soybean nutrient solution),the root dry weight,root to shoot ratio and phosphorus content of plants were studied by solution culture to explore the efficiency of insoluble phosphate fertilizer in different soybean genotypes.The results showed that both of the soybean genotypes could secrete H+ and organic acids to external environment under low P stress.The major forms of organic acids exuded from the roots included citric acid,oxalic acid,tartaric acid and malic acid according to the result of HPLC.When citric acid soluble phosphorus(CHP) fertilizer was added into the culture medium,the different genotypes of soybean could use this insoluble phosphate effectively.Irrespective of either H+ or organic acids secretion,the efficiency of insoluble phosphate of genotype(nf37) tolerance to low phosphorus was significantly higher than that of P-sensitive genotype(Jihuang 13) under low P stress.These results suggested that different genotypes could secrete H+ and organic acids under low phosphorus stress which further accelerated root growth.The secretion and growth of root system showed significant difference between phosphorus efficient and phosphorus sensitive genotypes.This could have caused the different efficiency of the insoluble phosphate absorption and utilization of different soybean genotypes.