Abstract
The authors reported two types of wheat in relation to photoperiodism of the varieties, one type of which was not affected as to their heading dates by a short day treatment, and the other type showed delayed heading dates by a short day treatment throughout the growing period as described in the second paper of this series. Using wheat varieties having different growth habits, the authors clarified the influence of short day treatment on the wheat growth, and especia1ly, the effects of different durations of short day treatment on the change of growth habit and on the delay of heading dates were examined. The results obtained in these 3 years tests are summarized as follows : a) Results obtained in 1956-'57 Varietal difEerences regarding the delay of heading dates by short day treatments (1O hours daylight) were tested among the varieties in 4 plots with 40 days interval from January 7 to May 6. In the varieties showing delay of heading dates by short day, their heading dates were prolonged only in the plot where the short day treatment was applied from March 27 to May 6 (about 40 days before the heading stage), and in the varieties showing no delay of heading date their heading date, were not prolonged by short day. b) Results obtained in 1958-'59 Varietal differences in the delay of heading dates, by the short day treatments were tested among thevarieties in 6 plots with 10 days interval from April 3 to May 23. In the varieties showing delayed heading dates by short day, their heading date. were prolon, ged in all the plots treated with short day. The plant height of the varieties belonging-to this group was about 20 cm in the elongation. stage. c) Results obtained in 1959-'57 Varietal differences in the delay of heading dates. by short day treatments were tested among the varieties in 8 plots with 10 days interval frorcL Feb. 22 (about 40 days before the heading date for early varieties) to May 3. Only in the varieties., showing delayed heading dates by short day their heading dates were prolonged, while the heading: dates were not prolonged in the varieties not influenced by short day.
