• 作者： 許東暉
• 作者服務機構： 臺灣省農業試驗所
• 中文摘要： In order to know the effect of temperatureto different type of rice varieties, an experimentusing two Japonica and two Indica rice varietisin the period from repeoductive to harvestingstage was conducted at Phytotron of TaiwanAgriculture Research Center. The informationobtained from this experiment will help to solvethe yielding problem of second cropping in thenorthern Taiwan. Results obtained from this experiment wereas follows:1. It was found that at reproductive stage, high temperature 25℃ (while 20℃ at night) gave higher grain yield in both Japonica and Indica rice varieties. Higher grain fertility and percentage of full-developed grains contributed most to the increasing of grain yield.2. In the early growth stage of the second crop season, the tillering number of Japonica type was found decreased due to higher temperature, but incontrast, higher tempera- ture enhanced the tillering ability of Indica type. However, under controlled temperature 25℃ (20℃), no effects was found in Japonica type, but in Indica, due to low grainfertleity and low percentage of filled grain, compared with the grain yield of Japonica type, 33% decreased was found.3. Different temperature reactions at reproduc- tion stage were found between two type of rice varieties. Ingeneral, Japonic type show more tolerant to low temperature than Indica. The reaction of low temperature was nearly the same among Jadonica varie- ties, but significant differences were found among Indica varieties while Hsinch- Aichueh-chien showed stronger.4. From reproductive stage, under the con- trolled temperature of 20℃ (while 15℃ at night), rapid decrease in grain yield was found in both Indica and Japonica type varieties. Especially, Japonica type varieties showed more marked decrease. Compared with 25℃ (20℃) treatment, only one third the grain yield was obtained. It seems that critical temperature is about 25℃ for Japonica rice and over 25℃ for Indica rice.5. In the northern part of Taiwan, the tem- perature of the second cropping after repro- ductive stage is gradually (Fig. 1), ranged from 17-23℃. This low temperature will affect the development of pollen grains, pollination, and fulfilment of seed sets. Therefore, the lower yield of rice in the second cropping not only is attributable to high temperature at the tillering stage, but also due to low temperature at the repro- ductive and harvesting stage.6. After reproductive stage, 25℃ (20℃) treat- ment can shorten the growth duration than that of 20℃ (15℃) treatment, but at this stage no effects was found on the plant height. On the contrast, at vegetative stage plant height was abiously affected by the heighttem perature. Therefore, development ofvarieties with shorter plant height to avoid lodging will increase the yield in the second cropping.7. The feasible way to increase the yield of the second cropping are: (1）Increasing panicle number and grain fertility via the crosses between Indica and Japonica type varieties. (2) Developing chilling tolerant and early maturity varieties will facilitate the adjustment of seeding date, and make the avoidance of low temperature at later growth stage become possible. (3) Developing Indica varieties which show strongly resistant to bacterial leaf blight and tolerant to low temperature. (4) Improving the cultural practice for increasing the panicle number in panicle weight type varieties or the panicle weight in panicle number type varieties. (5) Changing the cultural pattern from transplanting into direct seeding. Hence it can increase the tillering, shorten the growth duration, save labor and increase the yield. (6) Improving the application method of fertilizers. (7) Strengthen the study upon the effect of chemicals on rice at unfavorable cir- cumstance. (8) Using Agricultural Chemicals carefully, especially at later. growth stage, to avoid harms caused by low temperature.
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