Scaffold whorl

The first three to four branches on a trunk uniformly spaced. Related Images:

Radial spacing

The horizontal spacing of branches around a trunk. Related Images:

Primary growth

Growth that occurs via cell division at the tips of stems and roots. Related Images:

Pollard

A method of tree pruning that involves heading back severely to main branches each year so as to produce a thick, close growth of young branches. Related Images:

Perennial

A plant that lives more than two years and produces new foliage, flowers, and seeds each growing season. Related Images:

Nucleus

The organelle within a cell that contains chromosomes and thus controls various cellular processes, including division into new cells. Related Images:

Lenticel

A small opening on the surface of fruits, stems, and roots that allows exchange of gases between internal tissues and the atmosphere. Related Images:

Lateral meristem

Cylinders of actively dividing cells that start just below the apical meristem and are located up and down the plant. Also called the vascular cambium. Related Images:

Abscission layer

Specialized cells, usually at the base of a leaf stalk or fruit stem, that trigger both the separation of the leaf or fruit and the development of scar tissue to protect the plant. Related Images:

Abscission

The dropping of leaves, flowers, or fruit by a plant. Can result from natural growth processes or from external factors such as temperature causing dormancy or chemicals. Related Images: