Abstract
Photosynthetic and root respiration rates were investigated in relation to tree growth of four 7-year-old Japanese persimmon (Diospyros kaki Thunb.) cultivars. The differences in ecological characteristics and adaptability to warm climate among the cultivars are discussed.
1. Increases of trunk girth during the growing season were greater in the early-maturing cultivars 'Tone wase' and 'Nishimura wase' than they were in the relatively latematuring cultivars 'Fuyu' and 'Hiratanenashi'. In autumn, the total sugar contents of the non-bearing 'Fuyu' shoots were highest, whereas its starch contents were lowest among the 4 cultivars.
2. The photosynthetic rate of a single leaf in early July was high in 'Fuyu' and equally low in 'Hiratanenashi' and 'Tone wase'. In early August, however, photosynthetic rates were high in 'Hiratanenashi' and 'Tone wase' and low in 'Nishimura wase'.
3. There were no significant differences in seasonal changes in root respiration rate among the cultivars. However, in mid-August, the root respiration rates at 30 °C were lower in 'Fuyu' and 'Nishimura wase' than they were in 'Hiratanenashi' and 'Tone wase'; there were no differences at 25 °C. These results show that tree growth of the early maturing cultivars was greater than that of relatively late-maturing cultivars in the warm climate; 'Hiratanenashi' and 'Tone wase' which maintain higher photosynthetic rates during the summer seem to be more adaptable to the warm climate than the other two cultivars.
