Auxins - Apical Dominance
The role of auxins in controlling the apical dominance was shown by the experiments done by Skoog and Thimann with the broad bean plant. They removed the terminal bud. This resulted in the development of lateral buds and branching occurred. If an agar block containing auxins was placed after the removal of apical bud, no growth of lateral buds occurred. This meant that the role of terminal bud in suppressing the growth of lateral buds can be substituted by auxin. The agar blocks containing auxins is playing the same role as the apical bud. It was inferred that auxins present in the shoot apex might be playing a role in apical dominance. As auxins could be isolated from the terminal bud, it was believed that shoot apex is also the site of synthesis of auxins.