Abstract
During the panicle formation period, paddy plants were treated under low air temperature in the nighttime at various grades and the unfertilized grains were observed. The results are summarized as follows. (1) As the 1st experiment, varety "Fujiminori" at the reduction division stage of pollen mother cells was treated under 15°C for 11 hours in the every nighttime for six nights running. But the unfertilized grains did not increase so much. (2) As the 2nd experiment, variety "Hatsunisiki" was divided into five periods during the panicle formation period and at each period was treated under 8.25°C for 8 hours in the every nighttime for three nights running. But the unfertilized grains did not increase by every treatment. (3) As the 3rd experiment, variety "Sekiminori" at the reduction division stage of pollen mother cells, was treated under 5.1°C for 8 hours in the nighttime. But the unfertilized grains did not increase at all. It may be given as the conclusion that the efect of low temperature in the nighttime during the panicle formation period on the unfertilization of grains of paddy plant was unexpectedly small so far as the experiments mentioned above are concerned.
