Abstract
We analyzed the relationships between the yearly variation in sprouting, flowering and full bloom time of the 8 main cultivars of Japanese persimmon and air temperature in the Faculty of Agriculture, Kochi University between 1985 and 2004.
The monthly air temperature for March, April and May tended to rise at an annual rate of 0.084, 0.108 and 0.142°C, respectively. Along with this transition, the sprouting, flowering and full bloom time in the main 8 cultivars of persimmon tended to accelerate at rate of 0.45, 0.53 and 0.47 days per year, respectively. On average, between 1985 and 2004, the sprouting time of ‘Hiratanenashi’, Fuyu and the average of 8 persimmon cultivars were 21, 31 and 25 March, respectively, the flowering times were 5, 14 and 9 May, and the full bloom times 10, 18 and 14 May, respectively. There were high positive correlations between the times of flowering and full bloom and the time of sprouting in the 8 main persimmon cultivars. There negative correlations between the temperature during February and March and the sprouting time of 8 persimmon cultivars. There were negative correlations between the mean temperatures in February, March and April and the flowering and full bloom times of 8 persimmon cultivars, respectively. Average correlation coefficient values between the mean temperature of April and the flowering and full bloom time of 8 cultivars of persimmon were -0.88*** and -0.89***, respectively.
Based on these findings, it was thought that the early sprouting, flowering and full bloom of persimmon cultivars in the recent 20 years has been due to the rising of temperatures between Feb. and May due to global warming.
