2002 Volume 71 Issue 3 Pages 394-402
An early warning system for preventing the decrease in rice yield by cool summer damage in the whole Tohoku area is constructed. This needs to predict the developmental stages of rice plants from the effective accumulative air temperature above 10°C. The panicle development model, which predicts the time of pollen mother cell differentiation, meiosis, pollen ripening and heading was constructed using the effective accumulative temperature. The model was made by grown in a Gradiotoron with a daily mean temperature gradient from 18 to 26°C, and modified considering the difference in heading date between the main stem and the whole tillers in the field. The kernel developmental model, which predicts the time of milk ripe, dough ripe, yellow ripe and full-ripe stages from heading stage. The values of effective accumulative air temperature were decided in the field at Morioka in 1998 and 1999 for 12 leading cultivars of Tohoku District. The mean error of heading date and full-riping date predicted by the model in the 12 varieties at Morioka in 2000 was 1.2 and 2.1 days, respectively. The usefulness of these models was practically validated in the rice growers'fields in Miyagi and Yamagata Pref. Furthermore, the usages combining these two models with the leaf age predicting model reported previously make it possible to predict the dates of each developmental stage from rooting to full-ripe stage.
