Abstract
Dynamic states of water in seeds of rice (Oryza sativa L., cv. Hinohikari) plants grown at low/high temperatures during seed maturation were examined by NMR relaxation times (T_1 and T_2). Dry weight of grain grown at 20℃ gradually increased while both 25 and 30℃ enhanced growth rate at early- to mid-stage. T_<1s> in the seeds treated by three different temperatures related to their water content until 36 DAF (days after flowering). T_2 values of grain treated both at 25 and 30℃ sharply dropped to less than 1ms after 22 DAF, while those treated at 20℃ remained more or less unchanged until 29 DAF. Therefore, the low temperature maintained free water in grain one week longer than the high temperature treatment. The 20℃-treatment produced thin rice kernels which were lower than 1.8mm in thickness, while 30℃-treatment enhanced the kernel size over 2.0mm in thickness. The present results indicated that the ^1H-NMR spectroscopy was useful for early diagnosis of temperature stresses on rice kernel development.
