Allelopathy Among Some British Grassland Species: II. Influence of Root Exudates on Phosphorus Uptake

SUMMARY Root exudates from Anthoxanthum odoratum, Lolium perenne, Planltago lanceolata or Trifolium repens, or a control solution, were applied to each of the same four species. In Experiment 1 both the donor and receiver plants grew in sand culture; leachate from the donors was applied to the root medium of the receivers at intervals throughout their 31 months of life. In Experiment 2 both donors and receivers grew in water culture; the receivers were treated with root leachate for three days and then their P32 uptake over 4 h was measured. In both experiments there were significant differences in uptake of phosphorus between treatments: sometimes uptake of phosphorus was greater in the presence of plant exudates than in the control and sometimes it was less. For two species, the Anthoxanthum and Trifolium, there was good agreement between the results of the two experiments. The other two species showed differences in the shortterm experiment which failed to appear in the longer-term Experiment 1. A supplementary experiment showed that the effects were not due to pH differences between the leachates. If each of the two main experiments is considered alone alternative explanations of the results are possible, but where the two agree they provide strong evidence for effects of root exudates on phosphorus uptake.