The present study was done to know the relationship between the chlorosis expression induced by cooling a certain part of the rice seedling and the starch accumulation in the leaf blade. One type of the chlorosis expression may be induced by the inhibition of chlorophyll precursor formation, which is expressed by cooling the base of leaf sheath.Another one may be caused by the destruction of chlorophyll due to the excessive starch accumulation in leaves, Experiments reported here were carried out to clarify the relationships among the chlorosis expression, the starch accumulation in the leaf blade and the sensitive parts of plant to low temperature. (1) When the rice seedling was grown under low temperature and the base of leaf sheath was cooled at 15°C, the starch accumulation was not observed in the leaf blade showed typically chlorosis. This fact implies that the chlorosis caused by the inhibition of chlorophyll precursor formation has not relations with the starch accumulation. (2) When the root of rice seedling was cooled at 15°C, the starch accumulation was clearly observed in the leaf blade and the discoloration on the top of leaf blade was recognized, but under low light intensity was not. This may imply that the discoloration of rice seedling under low temperature is induced by the cooling of root. And the stronger light intensity was given, the more sever starch accumulation was observed. (3) If the base of the leaf sheath in rice seedling is cooled at 15°C, the starch accumulation was temporally observed in the expanded leaf or the expanding leaf, but the discoloration was not observed, and then the accumulated starch diminished as time passed.

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Effects of light and tempeature on rice plants in the vegetative stage was examined with special reference to the emergence and elongation of their tillers. The varieties used were Zuiho, sensitive to light, and Norin No.20,sensitive to temperature, and to them were added two more varieties, different in plant type, Norin No.1 (many panicle type) and Zosan No.1 (heavy panicle type). In the experiment, which was carried out in the growth cabinet, light and daek temperatures were combined, their averages were maintained at 18.5℃ (L), 24.5℃ (M) and 30.5℃ (H), and the difference at 7℃ in each combination. The light period was controlled so that it could be 12 hours. The results were : 1. As the temperature grew higher, the leaves of the main stem developd more speedily according to which primary tillers also emerged. 2. In the three varieties except Zosan No.1,the first tillers in primary tillering emerged in the M and L combinations, while in the H combination they did not in any of the varieties. 3. No secondary tillering could be observed in Zosan No.1 in the H combination, suggesting a strong control by high temperature. 4. In principle, primary tillering should occur in accordance in time with the emergence of the leaves of the main stem. However, the accordance was brorken under some temperature conditions; Zosan No.1 showed even a contrary tendency. 5. Tillering does not synchronize with the emergence of the leaves of the main stem under unfavorable conditions. As the conditions grow favorable, however, tiller buds differentiated at every node grow up to be tillers to elongate, and the typical accordance system works under the most favorable circumstances, though adaptability for their environment vary to some extent with the properties of varieties.

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[in Japanese]

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The gel consistency test, a simple and rapid method of testing eating quality of rice, was examined in relation to its applicability to the japonica varieties. The gel consistency value (the length of the gel) of the Tohoku varieties was longer than that of the Hokkaido varieties. Among the Tohoku varieties, difference of the gel consistency value was recognized, but didn't correspond to the eating quality. The gel consistency test may not be used in screening lines for good eating quality in rice breeding program of Tohoku district.

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