Effects of the growth stage at transplanting of paddy rice seedlings on heading date and floral sterility caused by low temperatures - in the cool summer of 2003 in Miyagi prefecture.

摘要

The heading date and ripening percentage of all stems of rice seedlings in each hill, in relation with cool summer damage, was studied in Miyagi prefecture, Japan in 2003. During that year, low temperature and insufficient sunshine persisted from June onwards, for a long period of time, and floral sterility due to low temperature occurred frequently. Heading date was earliest in plants transplanted during the middle seedling stage (MS), followed by those transplanted during the young seedling (YS) and nursling seedling (NS) stages. Heading period of MS, YS and NS was 11, 13 and 9 days, respectively. The difference in 50% heading dates between MS and YS was 4.7 days, and between YS and NS, 4.2 days. Regardless of the growth stage at transplanting, later heading date from 10 to 20 August resulted in higher percentage of ripening on stem. The ripening percentage of stems headed after 20 August was nearly the same. The weight of brown rice per unit area was lower in MS plants due to cold-induced sterility. The damage from cold-induced sterility can be mitigated by using the seedling types..