The physiological effects of Br on the tobacco seed vigor (CVNC89) and the growth and development of the tobacco plant (NC89) have been studied by using field culture and hydroponics for two years (1986, 1987). The results showed that after submergence in 0.05 ppm or 0.01 ppm solution for 24 hours, the absorbing oxygen, ethylene production and germinating rate of the seeds were increased. We also found that the dry weight and length of the roots of the treated seeds were obviously increased. In the experiment of the foliar application with 0.01 or 0.05 ppm solution for two or three times, we observed that there were several effects of Br on tobacco plants namely : (1) raising photosynthesis, chlorophyll content of the leaves, (2) promoting the growth of the leaf area and raising the leaf weight, (3) having a certain regulation of transportation; distribution and accumulation of P among the upper, middle and lower stalks, (4) raising the vigor and dry weight of roots , and significantly increasing ATP and free amino acid content in roots and stimulating roots to absorb and accumulate more P, (5) promoting IAA synthesis and inhibiting ABA synthesis, (6) significantly increasing nicotine content, free amino acid, total fat, polyphenol and reducing sugar in the leaves etc, (7) improving the quality and yield of the tobacco leaves.