The effects of shading on translocation of 13C- photosynthates between lateral branches during the rapid growth period of cherry, pear, and Japanese persimmon fruit.

摘要

The effects of shading on the translocation of 13C-photosynthates between 3- or 4-year old branches on mature trees during the rapid growth stage of cherry (cv. Nanyoh), pear (cv. La France) and Japanese persimmon (cv. Hiratanenashi) fruits were investigated. In all fruit trees, a very small quantity of 13C-photosynthates was exported into neighbouring lateral branches for 44-72 h after a basal or terminal lateral branch was exposed to labelled CO2. When branches except that fed with 13CO2 were shaded to about 50% of full sunlight from 5 days before to 3 days after the exposure, 13C-photosynthates did not translocate into the shaded branches in all 3 species. The data on the distribution of 13C atom percentage excess among several organs within branches fed with 13CO2 indicated that transport of photosynthates from older branches to younger shoots was predominantly acropetal. Therefore, it was concluded that the carbon budget of the 3- or 4-year-old lateral branches has the characteristics of a closed system during this phase of rapid fruit growth. Improvement of the light environment around the fruit bearing portion will be important at this stage, because photosynthates synthesized by leaves on adjacent, lower lateral branches do not contribute much to fruit growth.