Axillary bud


The axillary bud is an embryonic or organogenic shoot located in the axil of a leaf. Each bud has the potential to form shoots, and may be specialized in producing either vegetative shoots or reproductive shoots. Once formed, a bud may remain dormant for some time, or it may form a shoot immediately.

Overview

An axillary bud is an embryonic or organogenic shoot which lies dormant at the junction of the stem and petiole of a plant. It arises exogenously from outer layer of cortex of the stem.
Axillary buds do not become actively growing shoots on plants with strong apical dominance. Apical dominance occurs because the shoot apical meristem produces auxin which prevents axillary buds from growing. The axillary buds begin developing when they are exposed to less auxin, for example if the plant naturally has weak apical dominance, if apical dominance is broken by removing the terminal bud, or if the terminal bud has grown far enough away for the auxin to have less of an effect.
Axillary buds can be used to differentiate if the plant is single-leafed or multi-leafed. Simply count the number of leaves after an axillary bud. If there is only one leaf, then the plant is considered single-leafed, if not it is considered multi-leafed. An example of axillary buds are the eyes of the potato.

Effects of auxin

As the apical meristem grows and forms leaves, it leaves behind a region of meristematic cells at the node between the stem and the leaf. These axillary buds are usually dormant, inhibited by auxin produced by the apical meristem, which is known as apical dominance.
If the apical meristem is removed, or has grown a sufficient distance away from an axillary bud, the axillary bud may become activated. Like the apical meristem, axillary buds can develop into a stem or flower.

Diseases that affect axillary buds

Certain plant diseases - notably phytoplasmas - can cause the proliferation of axillary buds, and cause plants to become bushy in appearance.