Studies on Life and Death of Tillers already Developed in the Rice-nursery Caused after Transplantation Ⅲ Effect of plant growth regulators on promotion of the growth of tillers on the low position of nodes

With a view to searching for a means available to foster the growth of tillers on the low position of nodes of rice seedlings in order to contribute to rice cropping in warm localities, it was made to investigate whether or not the application of plant growth regulators, especially TIBA as anti-auxin and B-nine as plant growth retardant, to rice seedlings has similar effects to those of a low condition of soil temperature on hindrance of top growth and promotion of growth of tillers on the low position of nodes, and the following results were obtained. 1) Foliar application of 1000ppm TIBA or 3000ppm B-nine at a time of transplantation, is effectual for an increase in the number of productive stems under a condition of high temperatures. B-nine, however, excels TIBA in the effect to some extent. 2) Each of two substances causes tillers on the comparatively low position of nodes to emerge early, proving the possibility of its application to rice cropping. 3) Although foliar application of TIBA has no effect on the development of tillers grown in the nursery into productive stems, that of B-nine is, provided that seedlings are excellent in quality, effective and moreover, makes an emergence of secondary tillers earlier. In conclusion, it is safe to say that foliar application of B-nine to rice seedlings is one of means effectual to assure an increase in the number of productive stems at an earlystage of growth through practical utilization of tillers on the low position of nodes