Stimulatory effects of BRs on elongation are among the most documented physiological effects. It has been observed in many assay systems such as radish,tomato, sunflower and cucumber hypocotyls, normal and dwarf pea, mung bean and azuki bean epicotyls, Arabi-dopsis peduncle, and wheat coleoptiles (Brosa, 1999). However, BRs have been shown to promote elongation of vegetative tissue in a wide variety of plants at very low concentration. Recent work of Wimolphan (2004) revealed that wheat plants applied with the BR at only 0.005 to 0.02 ppm were significantly taller than untreated wheat plants. Obviously, cell elongation is associated with an increase of acid secretion. Thus, the stimulation of elongation in vegetative tissue is confirmed by BRs action.