Abstract
Effects of brassinolide (BR) on growth and developmental processes were examined in wheat plants applying the solution at various growth stages and at various concentrations. The results are summarized as follows: 1. Elongation of root, stem and leaf was not promoted by the treatment but rather a little inhibited at higher concentratiens (Fig. 1). 2. Formation of primary roots of seedling, tillers and spikelets was promoted by the BR-treatments. The number of productive tillers decreased, though that of total tillers increased by the treatments (Figs. 1∼5). 3. Heading was delayed by the BR-treatments (Fig. 4). 4. The effects of BR on ear-and grain yield were quite different depending on the growth stages at which the treatments were given. The BR-treatments before anthesis resulted in reduction of yield mainly due to decrease in productive tillers. On the other hand, the treatment during the ripening period (from anthesis to full maturity) considerably increased ear-and grain yield (in ear weight per plant, 15%) as a result of improvement in set and filling of grains, especially in inferior ones (Figs. 6, 7). 5. Photosynthesis was promoted a little by the leaf treatment of BR. However, the frequent application extending to later stages of leaf ontogeny brought about reduction of photosynthetic rates of leaves due to acceleration of senescence (Figs. 8∼10). 6. The BR-treatment scarecely affected total dry matter production (Table 2).
