Phytomers are functional units of a plant continually produced by root and shoot meristems throughout a plant's vegetative life-cycle. A typical phytomer consists of a node to which a leaf is attached, a subtending internode, and an axillary bud

Axillary bud

The axillary bud is an embryonic shoot which lies at the junction of the stem and petiole of a plant.As the apical meristem grows and forms leaves, a region of meristematic cells are left behind at the node between the stem and the leaf. These axillary buds are usually dormant, inibited by auxin...

at the base of the leaf.

Initially, a young plant will only produce phytomers at its apical meristems but later in development, secondary meristems will begin to form and phytomers will be formed on this lateral plant growth.