Studies on the Limit of Possibility of the Increase in Number of Leaves and Grains of the Main Stem of Rice Varieties.

1.The influence of temperature and day-length during the nursery period on the heading time and the numter of leaves of the main stem was investigated with 16 varieties of rice in order to study on the relation of the number ofleaves of the main stem with tbe limit of possibility of the increase of the crop. During the nursery period(34 days)the materials were kept at a hightemperature or at a low temperature at night under the short day treatment. 2.In the case of early varieties such as ”Hayasio”,”Eiko”or “Tomoe-masari”(remarkably sensible to high temperature and dull to short day-length),the premature heading occurred at the main stem under the condition of naturaltemperature or high temperature at night showing the decrease in number ofleaves of the main stem, and the delay of the heading occurred under a low temperature condition at night showing the increase in number of leaves of the main stem. 3.The incompetency of heading of the main stem occurred in ”Norin No･22” and‘‘Norin N0.37” under the condition of high temperature at night and short day-length.These middle-season varieties are dull to high temperature and remarkably sensible to short day-length. 4.1n the case of other varieties,no remarkable variation of heading time and in number of leaves of the main stem occurred under various conditions of temperature and day-length so far as the present experiment concerned.

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増加可能限界