Effect of Some Environmental Factors During Meiosis Stage on the Fertility of Grains in Rice Plant

[摘要] This investigation was carried out to clarify the effect of some environmental factors during the stage of meiosis on the fertility of grain in rice plant. In this study, two levels of each factor, light intensity (normal and 75% shading), daily air temperature (26 and 18°C), daily water temperature (26 and 18°C), air temperature at night (18 and 10°C), water tempetature at night (18 and 10°C), depth of water treated (5 and 20 cm), number of days of treatment (6 and 12 days) and varieties (EIKO and TOYOHIKARI), were used in a 28 factorial arrangement of treatment fractional to one block as described above, and four growth cabinets were used. The main effects and two-factors interactions were tested by means of single degree of "F" test at P = 0.05. The air and water temperatatures were changed at 9.00 a.m. and 5.00 p.m. The stage of meiosis in each panicle was estimated by the distance between auricles of the last two leaves and only the plants ranging from -5 cm to +2 cm in distance were used. Ten panicles were sampled in each plot. The results obtained in this investigation are summarized as follows: (1) According to the results of the variance analysis, the significance were found in all of the main effects and significant interactions were found between light intensity and varieties, and in many cases between the depth of water and the other factors. (2) The interactions of light intensity with air temperatures in day and night were not significant. This suggests that the damage to the fertility of grains are not increased by shading treatment when the air temperatures during meiosis is low. (3) Response of the combined environment of low temperature and shading to the fertility of grains varied with the vatieties, EIKO being sensitive and TOYOHIKARI insensitive, that is, in EIKO the damage to the fertility of grains is increased by shading treatment at the low temperature condition. There are some studies on this subject in the past, but the results are somewhat different in each studies. The reason of this difference among studies seems to depend mainly upon the characteristics of varieties used in them. (4) We reconfirmed that the water control in rice culture, especially at the stage of meiosis, is very important for increasing the fertility of grains when cool air temperature. (5) Main informations obtained in this study for testing the tolerance to cold weather or water of rice plants are: (a) If air temperature could be controlled, water temperature is negligible. (b) The relationship between day and night temperature is not clear, so that the temperature may be controlled constant or alternate in the day and night. (c) The test should be done under the cooler temperature and shading conditions. (d) When the materials are tested in deep warer condition, a 20 cm in depth is recommended and its temperature may be controlled constant or altertiate in the day and night.

[学科分类] 农业科学（综合）