Abstract
Root growth in Japanese persimmon tree was monitored through observation of cell division in the root tips of fifteen-year-old 'Nishimurawase' trees. Forty root tips from twenty trees were collected at every sampling date, cooled immediately to 0 °C, and fixed with aceto-alcohol for 24 hours. The root tips of the Japanese persimmon tree can be either white or black ; these can distinguished by the blackish dermatogen in the terminal 5 to 10 mm of the root tips.
Before May 20 th, all root tips in the experimental sample were black. By June 14 th, 58% of roots were white. The number of white root tips decreased gradually after that days, and no white tips were observed on September 28 th.
Cell division occurred in both black and white root tips, but in April and May most cell division took place in the black ones. From June to September, most cell division was observed in the white tips. The mitotic index was low in April ; it increased suddenly in June, then decreased gradually until October.
Cell division in the root tips began when the air temperature was 12 °C ; its rate increased as the temperature rose. No relationship was observed between the rate of cell division in the root tips and amount of precipitation during that period.
