Virtual Museum of Canada
Jardin botanique de Montréal 
Centre for Forest Research

Orchestrating its growth

The bud at the end of the twig, or the terminal bud, is responsible for primary growth, as the branch lengthens. However, it must also prevent the lateral buds on the twig from growing as quickly as it does – if all the buds turned into new growth, the poor twig would crumble under its own weight!

So how does the terminal bud prevent the growth of nearby buds without affecting the others? By producing a hormone called auxin, which inhibits the growth of other buds. It is concentrated near the terminal bud, but is more diluted weaker farther away, affecting other buds less and less.

Photo of the lateral buds and the terminal bud on a twig of a rock elm (Ulmus thomasii)
Ulmus thomasii
© Jardin botanique de Montréal (Lise Servant)