2011 Volume 10 Issue 4 Pages 551-558
To determine the characteristics of carbohydrate competition, we investigated changes in 13C concentration and distribution rate in fruit-bearing branches of Japanese Apricot (Prunus mume Sieb. et Zucc.) ‘Nanko’ during fruit growth. We also investigated the effect of heavy crop load on 13C concentration and distribution rate in each organ of the whole tree and on the growth of the tree. In fruit-growth stage I, the 13C concentration and distribution rate in shoots were higher than those in fruits, however, fruits comprised about 30% of the 13C distribution rate. These findings indicated that the carbohydrate competition between fruits and shoots exists from the early fruit growth stage. The 13C concentration and distribution rate in fruits was the highest in all organs during stage II. Especially, the 13C concentrations in the stone and kernel of the fruit showed significantly higher values. During this stage, the carbohydrate distribution rate in fruit was about 60% and higher than that in shoots at about 40%. In fruit-growth stage III, the 13C concentration in fruit declined in comparison in that in stage II; however, the 13C distribution rate remained about 40%. The 13C concentration in shoots and roots of trees with a heavy fruit load were lower than those of trees with a normal fruit load, and the carbohydrate distribution rates in the former were also lower than those of the latter. A tree with a heavy fruit load showed leaf rolling and etiolation, earlier defoliation, restraint of emerging vigorous shoots, and an increase in dead twigs. In conclusion, it was clear that the carbohydrate competition between shoots and fruit is most significant during fruit-growth stage II. It was thought that trees grown with a heavy fruit load become weaker due to restraint of carbohydrate translocation to shoots and roots.
