Organ-dependent seasonal dynamism of three forms of carbohydrates in Japanese apricot

• Changes in amounts of carbohydrates in Japanese apricottree were evaluated until May of the following season.
• Reserve carbohydrates mainly contributed to growth of young shoots and fruits.
• Carbohydrates assimilated in each month contributed to different organs.
• In the beginning of May, large amount of carbohydrates assimilated last year presented in the form of the CWM of older organs.

Changes in concentration of carbohydrates in three forms—soluble sugars, starch, and cell-wall material (CWM) assimilated each month from summer (August; 2 months after harvest) to late fall (November; just before defoliation)—in organs of Japanese apricot (Prunus mume Siebold et Zucc.) Nanko” were determined until May of the following season by providing 13CO2. 13C concentrations in the nonstructural carbohydrates (soluble sugar and starch) in the foliar and flower buds were higher than those in the current twigs and fine roots, suggesting that these organs are large sinks of reserve carbohydrates. However, they decreased sharply along with growth and were low in all the organs at the beginning of May. In contrast, a large amount of 13C was fixed in the CWM of older twigs. These results indicate that reserve carbohydrates contribute to the growth of young shoots and fruits until the beginning of May, after which their growth depends on current assimilates. Carbohydrates assimilated in August–November were mainly transported to twigs, roots, trunk, and flowers, respectively. These findings show that carbohydrates assimilated in each month contribute to different organs. Thus, leaves should be maintained healthy until defoliation to produce substantial amounts of carbohydrate reserves for stable fruit production from Japanese apricot tree.