The effects of indole-3-acetic acid or IAA (0.1, 1, 5, 10 µg/g) and 6-benzyladenine or BA (1, 10, 20, 50 µg/g) and their interactions on the extension growth of hypocotyl segments of bean (Phaseolus vulgaris L. cv. Sutton's Premier) were examined. IAA at 1 µg/g proved optimal and exhibited 14.7, 19.5 and 5.6% stimulation after 24, 48 and 72h of incubation. BA at the concentration of 10 µg/g stood as optimal, recording 11.6, 12.0 and 4.0% stimulation after 24, 48 and 72h respectively. The combination of optimal concentrations of IAA and BA(1 µg/g IAA + 10 µg/g BA) resulted in 27.7 33.0 and 11.1% stimulation at the end of 24, 48 and 72h respectively. Thus, IAA in conjunction with BA produced higher growth stimulation which was more than additive (synergism).
