THIAMINE (VITAMIN-B1) SEED TREATMENT ENHA NCES GERMINATION AND SEEDLING GROWTH OF BEAN (PHASEOLUS-VULGARIS L) EXPOSED TO SOAKING INJURY

Seed treatment with thiamine mononitrate significantly increased germi nation rate of bean ('Phaseolus vulgaris L.) seedlings germinated at h igh soil moisture levels and low night-temperature (5 degrees C). Bene ficial effects of thiamine applications on germination were also obser ved served in soil-free germination tests when the seeds were submerge d in water for 1-4 d at 18 degrees C. Optimum response was achieved at thiamine concentrations of 3 mM, applied during the first 24 h of inh ibition. As an early response to the thiamine treatment, vital stainin g with triphenyltetrazolium chloride revealed a lower proportion of da maged tissue of the embryonic axes. In later stages of seedling develo pment, thiamine seed treatment resulted in a lower proportion of abnor mal seedlings with malformations of the shoot apex and of the primary leaves. The beneficial effect of thiamine was more pronounced when the temperature during submergence was kept at 25 degrees C compared to 5 degrees C. There was no response to thiamine applications when the ge rminating seeds were exposed to low temperature treatments only. The t hiamine effect could be mimicked by raising the osmotic potential of t he incubation medium, indicating a relationship a to soaking injuries. The results suggest that normal seedling development may be impaired be thiamine deficiency in the embryonic tissue induced by soaking inju ry, whereas low temperatures are not involved as a stress-factor.