How do trees decide when and where their branches grow?
In: Biology
To complete and go more in depth on what was already answered, it is a mix of influences from genetics and environmental conditions (as for everything in biology actually). A stem or a branch usually end with a bud (called apical bud) which contain a special group of cells called a meristem. Meristems are where cell multiplication happens in a plant and so are what allow a plant to grow. During the growth season, this apical meristem will produce new cells at the base of the bud and those cells will then elongate, which will make the branch grow longer. As others said, this process is controlled by hormones (the principal one being called the auxin), and those hormones are strongly sensitive to the environmental conditions. For example, light destroy the auxin, which will make the shadowed side of a stem grow more than the other side and the stem will “go” toward the light source.
Every now and then during this period, the meristem will produce a leaf and on the top of the junction between the leaf and the branch, a little piece of meristem will separate to create a new bud (called axillary bud). This bud will stay dormant until the next growing season (where there is different seasons) and then it will start to be active the same way as the apical bud (it actually is an apical bud at this point) and develop into a new branch. The rhythm and the places the leaves and the axillary buds will be produce is mainly controlled by genetics.
So to summarize, environmental conditions like light (but also wind, gravity, animal grazing,…) control the shape of the branches and where they go, and genetics controls when and where a new branch is produced.
Latest Answers