noun, plural: secondary meristems
(botany') A type of meristem that is involved in the secondary growth and thus gives rise to the secondary tissues of the plant
A meristem is comprised of indeterminate, actively dividing cells that give rise to differentiated permanent tissues. It may be primary or secondary.
A secondary meristem is a type of meristematic tissue that is responsible for the secondary growth in plants, i.e. growth in girth or thickness. It is opposed to the primary meristem that is involved in the primary growth, i.e. growth in height or length. Thus, a secondary meristem leads to lateral growth rather than to vertical growth as in the primary meristem. It also differs from the primary meristem in being derived from the permanent tissue. The primary meristem is derived directly from embryonic cells.
The secondary meristem is also responsible for giving rise to cells that differentiate into the secondary permanent tissues of the plant, e.g. phellem. An example of a secondary meristem is the lateral meristem (e.g. cork cambium and accessory cambia).
Being meristematic, the secondary meristem is comprised of undifferentiated (or partially differentiated), actively dividing cells. The cells are closely packed and as such intercellular spaces between cells are absent.