Genotypic variation in putilization of Cajanus Cajan (L.) Millsp under low-p stress and corresponded mechanisms

Genotypic variation of pigeon pea [Cajanus Cajan (L.) Millsp,cv. MD2, MD5 and MD7] in P uptake, P utilization and corresponded mechanisms were investigated by hydroponic experiments. Significant genotypic variations in P uptake and P utilization were found in pigeon peas grown in 1 μmol L-1 P solution. It was shown that MD7 and MD2 were higher P-efficiency genotypes, while MD5 was lower one. Significant increase in the ratio of root to shoot and the activities of acid phosphatase (APA) secreted from roots was found in high P-efficiency genotypes after the plants were treated with low phosphorus (P 1 μmol L-1) for 16 d, suggesting that the ratio of root to shoot and APA secreted from roots are involved in higher P uptake-efficiency of pigeon pea. Under low P stress, P content in plants of MD7 and MD2 was lower than that in MD5, while P utilization efficiency and the activities of APA in root apices were higher, indicating that high activity of APA in roots is one of the important reasons for plant utilizing P efficiently.