Fig. 1.
Plant responses to inorganic phosphorus (Pi) limitation. A low external Pi availability decreases the plant's internal P status. When the plant senses a low P status, P-starvation responses are up-regulated. P-starvation responses, depending on the species, include increased root-hair formation, root-cluster initiation and development, carboxylate exudation, P-uptake capacity, and mycorrhiza formation. Phosphite acts as an analogue of phosphate, and hence suppresses the typical P-starvation responses shown here. Based on Abel et al. (2002) and other references cited in the text.