Abstract
A model was developed to calculate the full-blossoming dates of cherry tree (Prunus yedoensis). This result was compared with that to calculate first-flowering dates, in order to detect the difference of response to temperature among the two phenophases. DTS-method, an accumulation model, taking account of nonlinear response against temperature, was applied to development of models. As a preliminary analysis, the temperature characteristics Ea, which represent the change in developing rates as a factor of temperature condition, was deduced, and the suitable value of Ea for full-blossoming (70 kJ mol-1) was in agreement with that for first-flowering of P. yedoensis.
The model of full-blossoming of cherry tree needed to determine other two suitable variables (starting date D2, and DTS accumulation required until full-blossoming date) than Ea value, for precise estimation. Suitable starting dates D2 fell within the range of DOY 20 – 60, reflecting the difference of the timing when temperature condition starts to influence on flower buds. Suitable DTS accumulation value, needed to reach full-blossoming status, was determined as 26.4 days. Estimated full-blossom dates showed the error of 1 – 3 days in root mean square error.
The suitable starting dates (D2) for full-blossoming were later than those for first-flowering. Furthermore, the suitable DTS value (determined as 26.4 days) accumulated from D2 until full-blossoming date, determined as 26.4 days, was somewhat larger than that needed until first-flowering status (23.8 days). Naturally the flower buds causing full-blossoming and first-flowering are distinct. The former may have been released from dormancy inadequately than the latter. Therefore, this lag of dormancy completion of flower buds, which come out on full-blossoming date, caused increment of DTS value required to be accumulated until flowering.
