Secondary growth

Secondary growth is an increase in stem or root girth produced by lateral meristems, especially the vascular cambium. It adds secondary tissues outside or inside the primary plant body.

Vascular cambium: A lateral meristem that produces secondary xylem inward and secondary phloem outward. Its divisions drive most secondary thickening in stems and roots.
Lateral meristem: A meristematic tissue that increases the diameter of stems and roots through cell division. Secondary growth is the thickening produced by these meristems.
Woody plant: A perennial plant whose stems or roots contain substantial secondary xylem and protective bark. Persistent cambial activity gives woody plants their characteristic thickened axes.
Dendrochronology: The dating and study of past events and environmental conditions using tree-ring patterns. Annual secondary xylem increments preserve dated records of growth conditions.
Vascular cambium development: The formation and maintenance of the meristem that generates secondary vascular tissues. Understanding its regulation explains how secondary growth begins and persists.
Cork cambium: A lateral meristem that produces cork cells outward and, in some plants, phelloderm inward. It replaces the epidermis with protective periderm as organs expand.
Apical meristem: A meristem at a shoot or root tip that produces primary growth in length. Its elongation contrasts with the girth increase caused by lateral meristems.
Tree: A perennial plant with a tall, self-supporting woody stem or trunk. Its trunk is a conspicuous product of prolonged secondary growth.
Wood: The structural material composed mainly of secondary xylem in trees and other woody plants. It is the principal accumulated product of secondary growth.
Cambial activity: The rate and seasonal pattern of cell division in vascular and cork cambia. Its environmental and developmental controls shape the amount and structure of secondary tissues.

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