Trunk Girdling at an Early Stage of Shoot Elongation Affects Dry Matter Production and Partitioning in Japanese Persimmon (Diospyros kaki L.) cv. Tonewase

The effect of trunk girdling at an early stage of current shoot elongation on tree growth and total dry matter production and partitioning in 3-and 4-year-old Japanese persimmon (Diospyros kaki L.) cv. Tonewase were determined.1. Girdles (5 mm width) made on trunks on 1 May inhibited current shoot, leaf and trunk growth. However, there were no differences in shoot number, total leaf number and specific leaf area (SLA) between girdled and non-girdled trees. Fresh weights of shoots and rootlets of girdled trees were ligher, and wood-leaf ratio and top-root ratio were higher, compared with non-girdled trees. Dry matter gains by shoot, leaf and rootlet of girdled trees during the growing season were slower, compared with non-girdled trees on nonbearing trees. Dry matter partitioning in current shoot was less, while in older wood of girdled trees, it was higher, compared with non-girdled trees. There were no differences in amount of dry matter gains per unit leaf area and per unit leaf dry weight between girdled and non-girdled trees.2. Regirdling the trunk on 21 April in the following year inhibited current shoot, leaf and trunk growth, and furthermore, decreased total leaf number. However, there was no difference in SLA between girdled and non-girdled trees. Fresh weights of shoots, leaves and rootlets of girdled trees were ligher and wood-leaf ratio and top-root ratio were higher, compared with non-girdled trees. Dry matter gains of shoots, leaves, fruits, roots and rootlets of girdled trees during the growing season were less than those of non-girdled trees. Dry matter partitioning to current shoot, leaf and rootlet was less, but greater in older wood and fruit of girdled trees compared with non-girdled trees. There were no differences in amount of dry matter gains per unit leaf dry weight between girdled and nongirdled trees.Inhibiting tree growth by girdling the trunk at an early stage of shoot elongation resulted in a reduction of dry matter production. This is attributed to 1) the smaller size and number of leaves and 2) the inhibition of new root growth by blockage of translocation of photosynthates from leaves to roots.