Abstract
Variety, Norin 14, was grown under four different levels of nitrogen application (no nitrogen; -N, usual dose: 1N, fifty percent more: 1.5N, and two times usual: 2N) at three locations, Nagano, Konosu and Tachikawa, with an aim of knowing the local differences in ripening process. Another cultural methods such as planting time and planting density were according to the customary practice of respective place. The results obtained are as follows: 1) During the period from transplanting, to heading, Nagano was characterized with the longest sunshine hours although air temperature was almost similar in three places. At the ripening stage, Nagano showed the lowest air temperature though there was no difference in sunshine hours in three places (table 1). 2) Period from transplanting to heading was similar in three places, but the period from heading to maturity differed markedly with places, ranging from 55 days at Nagano to 38 days at Tachikawa, thus indicating the lower the air temperature the longer the ripening period (table 1). 3) Velocity of carbohydrate translocation to the panicles depends on the temperature after heading; it was fast at Konosu and Tachikawa where temperature was high and very slow at Nagano having the lowest temperature (fig. 4). But the prolonged ripening period at Nagano caused a long-lasted accumulation of starch into panicles, resulting in the greatest accumulation by the end of ripening (fig. 5). In addition to this, lower temperature during the ripening stage is considered to be effective in reducing the respiratory conssumption of carbohydrate. 4) Thus the beneficial effect of low temperature at the ripening stage in causing the longer ripening period, although it related to slow translocation, was clearly visualized in the local comparison of the ripening process.
