Studies on the growth habit of wheat varieties. 4. Relation between temperature effect and photoperiodism and its effect on the growth habit of wheat

Abstract

The authors determined 3 main genetic factors affecting the growth habit of wheat in report 1. Among these 3 factors, E factor determines erect type, and both P and T factors control prostrate type though they differ in their effects on prostrate t ype. We also clarified changes in growth habit, elongation of plant height, and variation in heading date in 4 experimental plots, i.e., control, Iong day, short day (10 hours) in field culture, and normal culture in greenhouse as described in report 2. In this paper, we studied changes in growth habit, elongation of plant height, and variation in heading dates in 4 experimental plots ; control, 10ng day, short day (10 hours) in field culture, and normal culture in greenhouse, using the plants subjected to low temperature (O-2°C) treatment for 60 days and those not treated with low temper ature at the germinating stage. The results obtained are summarized as follows : 1) Varieties of erect type and those showing the prostrate type were different in their low temperature requirements at the seedling stage and there were varieties which required high temperature at young stage. Based on their behavior, we attempted to subdivide these varieties as follows: a. Varieties of erect type did not require low temperature at the seedling stage and the heading date was accelerated by either greenhouse culture or long day treatment (Shinchunaga and Norin 20). b. Among the 3 prostrate types, a variety belonging to the first type did not require low temperature at the seedling stage, but demanded long day for the change from prostrate to erect type in spring (Ceres). c. A variety belonging to the second prostrate type did not require low temperature at the seedling stage but needed high temperature, and it did not depend on long day for the change from prostrate to erect type (Wichita): ' d. Varieties showing the third prostrate type required both low temperature and long day fcr the changes from prostrate to erect type, and the effect of high temperature on the growth habit changes was mainly affected by day-light length (Pawnee, Norin 8 and Oinoue). Differences among the erect, prostrate, and medium types in their requirements for temperature and long day are shown in the following table. 2) Three kinds of prostrate type wheats seem to, be characteristic of the growth habit and the prostrate type appeared not only by low temperature but also by unfavorable environmental conditions. However, once after the prostrate type was changed into the erect one, the latter type did not change back to the prostrate type by unfavorab e environ mental conditions.