The Translocation of Photosynthetic Products from Mesophyll into Midrib in Flue-cured Tobacco Plant : II The distribution of translocated- 14C among various compounds in the veins of 1st order of branching and the midrib

摘要

To investigate the composition of photosynthetic products translocated from the leaf of flue-cured tobacco plant, 14CO2 was supplied to a part of mesophyll, and the distribution of 14C among various compounds in the veins of 1st order of branching and the midrib was traced during the period of 180 minutes after 14CO2 feeding. Results obtained were summarized as follows: 1) In the veins of 1st order of branching and the midrib, about 70% of the total 14C was found in sucrose, and a little amount of 14C in glucose and fructose. Therefore, it was concluded that sucrose was the main transport substance in flue-cured tobacco plant. 2) The assay of 14C-components of cationic fraction in the veins of 1st order of branching and the midrib showed that most of 14C in fraction was incorporated into serine at the time of 30 and 60 minutes after 14CO2 feeding, thereafter, 14C-serine decreased. On the contrary, the radioactivities in aspartic acid, glutamic acid, glutamine, and γ-aminobutyric acid increased with time. 3) Radioactive malic acid was found in the mesophyll and the veins of 1st order of branching, but not in the midrib, 4) In the veins of 1st order of branching, the incorporatibn of 14C into the insoluble fraction and the hydrolysis of the translocated 14C-sucrose were found to be more profound than those in the midrib. From these facts, it was inferred that the 14C translocated into the veins of 1st order of branching was more actively utilized for formation of the tissue, comparing with the 14C in the midrib.