Phosphorus deficiency enhances root exudation of low-molecular weight organic acids and utilization of sparingly soluble inorganic phosphates by radish (Raghanus sativus L.) and rape (Brassica napus L.) plants

Root exudates were collected from radish and rape plants grown in P sufficient and P deficient nutrient solution. In radish, tartaric, malic and succinic acids were the dominant organic acids which increased between 15 times (succinic acid) and 60 times (malic acid) under P deficient conditions. In another experiment in quartz sand culture supplied with either Ca3(PO4)2 or AlPO4, radish utilized P from AlPO4 much better than from Ca3(PO4)2 whereas the opposite was true for rape. The results demonstrated the role of a particular organic acid in mobilizing sparingly soluble P and were in accordance with the preferential growth of two plants on acid (radish) and calcareous (rape) soils in China.