Studies on optimum moisture content and heat-stable protein of rice seeds stored at room temperature

Chinese. 通过使用在不同气候区室温保存8年的两个不同类型水稻品种，测定水稻室温贮藏的最适含水量，以及在贮藏过程中种子中的热稳定蛋白的变化。通过发芽试验和热稳定蛋白的测定，比较贮藏8年后种子的发芽率、活力指数和热稳定蛋白的变化。在北京地区贮藏种子，籼稻桂早2号（Oryza sativa L. ssp. indica Kato）最适种子含水量为5.5%～6.0%，而粳稻幸实（Oryza sativa L.ssp.japonica Kato）为6.5%～7.0%。在南昌地区，籼稻最适种子含水量为4.5%左右，而粳稻为5.5%～6.0%。耐超干的籼稻品种桂早2号种子中有一条分子量为39.4 kD的特异性蛋白条带，而不耐超干的粳稻品种幸实却没有这条带。当桂早2号种子发芽率为零时，该特异性热稳定蛋白条带消失。在分子量为41.6 kD处，桂早2号和幸实品种间的热稳定蛋白电泳图谱也存在差异。当幸实种子发芽率降至零时，该热稳定蛋白条带消失。在同一地区室温贮藏条件下，其最适含水量水平粳稻幸实高于籼稻桂早2号。而对于在不同气候地区贮藏，其最适含水量水平随该地区年平均温度和大于0℃积温升高而降低。发现的两类热稳定蛋白可能与水稻种子耐脱水性及其种子活力丧失有关。

English. The project investigated rice’s optimum seed moisture content (MC) in storage at room temperature. It also looked at the change of seed heat-stable protein using two rice cultivars stored in different climate zones for 8 years. The optimum seed MC and the change of seed heat-stable protein after storage for 8 years were compared using germination tests and heat-stable protein determination. The results showed that the optimum seed MC in Beijing was 5.5～6.0 for Indica cultivar Guizao 2 (Oryza sativa L. ssp. indica Kato) and 6.5～7.0 for Japonica cultivar Xingshi (Oryza sativa L.ssp.japonica Kato). It was 4.5 and 5.5 for Guizao 2 and Xingshi in the Nanchang area, respectively. The SDS-PAGE electrophoresis showed that a unique band of 39.4kD heat-stable protein appeared only in the seeds of Guizao 2. It was tolerant to ultra-drying, but it did not appear in the seeds of Xingshi, which was not tolerant to ultra-drying. This heat-stable protein band disappeared though while germination percentage of Guizao 2 reached zero. Different electrophoresis banding pattern was also displayed for a 41.6kD heat-stable protein in the two cultivars. An expected band didn’t show for Xizngshi with a zero germination percentage. A higher level of optimum seed MC in Japonica cultivar Xingshi comparing to Indica cultivar Guizao 2 was detected, if stored at room temperature in the same area. Optimum storage seed MC which varied in different climatic zones would decrease while annual average temperature and above zero accumulated temperature increased in a specific zone. The two heat-stable proteins indentified in this study were suggested to be related to seed dehydration tolerance and vigor loss.