Physiology

Abstract

Abstract Fluctuations in chemical composition of rice phloem sap was studied by varying environmental conditions. The sap was collected by a method similar to an aphid technique. The chemical condition and pH of the sap were fairly constant for several hours during sap exudation. However, concentrations of sucrose and ami no acids of sap collected from old plant tissues were higher than those from younger tissues. The sap from an insect resistant cultivar had lower concentrations of aspargine (Asn) than that from non‐resistant cultivars. N and P deficiency of the plant decreased Asn concentration of the sap, while K deficiency increased it. Hence, susceptibility to insect attack may be controlled by regulating the nutrient status of plants and by cultivar selections. Sucrose, glycine and serine concentrations of the sap were higher when exudate was collected in light than in darkness.