Table 1.

Multiple responses of plants under Pi deficient conditions (Raghothama, 1999).

Kind of Responses	Plant Responses
Morphological responses	Increased root:shoot ratio, changes in root morphology and architecture, increased root hair proliferation, root hair elongation, accumulation of pigments, proteoid roots, increased association with mycorrhizal fungi
Physiological responses	Enhanced Pi uptake, reduced Pi efflux, increased Pi use efficiency, mobilization of Pi from the vacuole to cytoplasm, increased translocation of Pi within plants, retention of more Pi in roots, secretion of organic acids, protons and chelators, secretion of phosphatases and RNases, altered respiration, carbon metabolism, photosynthesis, nitrogen fixation, and aromatic enzyme pathways
Biochemical responses	Activation of enzymes, enhanced production of phosphatases, RNases and organic acids, changes in protein phosphorylation, activation of glycolytic bypass pathway
Molecular responses	Activation of genes (RNases, phosphatases, phosphate transporters, Ca-ATPase, vegetative storage proteins, β-glucosidase).