Concentration of total, inorganic, and lipid phosphorus in leaves of white clover and stylosanthes

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Abstract
White clover (Trifolium repens L.) and stylosanthes (Stylosanthes hamata (L.) Taub.) were grown in soil at various rates of applied phosphorus (P). At each level of supply, the concentration of total, inorganic, lipid, and organic (minus lipid) P in leaves of different age was determined. In white clover, total and organic (minus lipid) P concentration declined with leaf age. Lipid and inorganic P concentration generally showed less decline. In stylosanthes, total and inorganic P concentration declined with leafage at a high level ofP supply. At lower levels, the concentration of all fractions showed little change with leaf age. The concentration of all the fractions, particularly inorganic P, increased with supply in both species. Changes in total leaf P concentration with age are interpreted as being partly a result of mobilisation of P from the organic (minus lipid) fraction whereas changes with P supply are thought to be mainly caused by changes in inorganic P. The concentrations of the fractions were much lower in stylosanthes than in white clover. Under the conditions used in this work, the ratios between lipid and total P appear to be similar in the two species, but the ratio of inorganic: total P appears to be higher in stylosanthes.