| Heilongjiang Province is located in the north of China and the temperature is on the low side. Rice is rather sensitive to temperature and temperature is the primary environment factor that affects rice output and quality in cold region. Cooling injury can be classified as such three types as delay type, sterile type and mixed type. Sterile-type cooling injury occurs at a rather high frequency in Heilongjiang and causes reduction of output of rice. As a result, the study of sterile-type cooling injury with respect to rice has great significance.In this research two varieties (lines) of rice of Cr-23 and Ha92-53 is selected to be treated in different temperatures during 4 to 12 days in phytotran and the designed temperature values is 13℃, 17 , 21℃ and 25 . The flowering time is observed and recorded and pollen shedding and germinating condition is examined after tassel. Once spikelet flowering is observed it is supposed that anthesis begins. Then the plants to be treated are moved into phytotran for temperature treatment. Flowering of each spikelet is recorded and marked and the spikelet marked is tracked and investigated with respect to their fertility.The experiment result indicated that spikelet fertility decreased with the increase of treatment time regardless of the condition of being before, during or after treatment. Detailedly, the influence of cooling temperature on fertility is minimal when treated after anthesis, medium before anthesis and maximal during anthesis. Comparatively, the cooling temperature resistance of Cr-23 is better than Ha92-53. The latter exhibited obvious reduction of fertility under the condition of cooling temperature. Spikelet fertility is also affected by the number of pollen shedding on stigma and germinated pollen grains. Our research indicated that spikelet fertiled normally when germinated pollen grains on one stigma exceeds six.
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