Sugar, Amino Acid and Inorganic Contents in Rice Phloem Sap

概要

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Rice phloem sap was obtained through severed stylets of brown planthoppers and its chemical composition was determined. Sucrose, the only sugar detected, was present at 17-25% (w/v) in the sap. Amino acids were present at a total of 3-8% (w/v) and were found to be mostly in a free form. The amount of bound amino acids was estimated to be small, if any were present. Among the free amino acids, asparagine (17-33% on a molar basis), glutamate (6-14%), serine (10-13%), glutamine (7-15%), threonine (5-6%) and valine (6-7%) were dominant, while cystine and methionine (0-0.2%) were present in minor amounts and γ-aminobutyric acid was not detected. The sap had a slightly alkaline pH (ca. 8.0). The inorganic constituents detected by electron probe x-ray microanalyzer were Na, S, P and K, with the K content being the highest. The osmotic pressure was estimated to be 13-15 atm. The amino acid composition of the plant parts was determined and the differences in the ease of phloem loading among amino acids were compared.
日本植物生理学会の論文