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 andγ-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
展开▼
