Portal de Periódicos da CAPES

Chemical Composition of Phloem Sap from the Uppermost Internode of the Rice Plant

1990; Oxford University Press; Linguagem: Inglês

10.1093/oxfordjournals.pcp.a077899

1471-9053

Hiroaki Hayashi, Mitsuo Chino,

Agriculture, Soil, Plant Science

The chemical composition of phloem sap from the uppermost internode of rice plants (Oryza sativa L., var. Kantou), one week after anthesis, was compared with that of phloem sap from the leaf sheath of a young seedling. The pure phloem sap from rice plants was collected by an insect laser technique. The phloem sap from the uppermost internode contained a high level of sucrose (573.8 mM) which was the only sugar detected. The concentrations of total amino acids, potassium and ATP were 124.8 mM, 40.4 mM and 1.76 mM, respectively. The concentration of sucrose was three times higher and the potassium level was one third as high in the internode sap as in the phloem sap from the leaf sheath. The total concentration of amino acids was almost the same, but the relative amount of each amino acid was quite different. The ratios of levels of Glu to Gln and of levels of Asp to Asn in the phloem sap from the uppermost internode were smaller than those in the phloem sap from the leaf sheath. The adenylate energy charge was 0.92–0.93 in both types of phloem sap. The amino acid composition of the phloem sap from the uppermost internode was compared with that of the phloem sap of the flag leaf and the endosperm sap of the same plant, one week after anthesis. The differences in composition along the phloem pathway suggest the selective translocation of amino acid.