Abstract:
In 2 glasshouse experiments, the effects of variations in phosphorus (P) level on concentration and distribution of total and labile P within wheat plants were examined to compare the sensitivity of various plant tests for assessing the P status of wheat. Total P was distributed unevenly within the plant: shoots had higher total P concentrations than roots, and concentrations in grain were markedly higher than in glumes or straw. Within wheat shoots, the concentration of total and labile P varied with stage of plant growth and the type and physiological age of the plant part analysed. In general, leaf blades had higher concentrations than their subtending sheaths. During the vegetative phase, the highest P concentrations were measured in immature tissues and the concentrations decreased progressively in older plant parts, except at luxury supply where total P was invariably higher in old leaf blades. Critical total P concentrations (CTPC) estimated for whole shoots decreased with advancing plant age beyond Zadoks Scale 13