sekundærvekst

Sekundærvekst is a botanical term referring to the increase in girth or diameter of stems and roots in woody plants. This growth is primarily driven by the activity of two lateral meristems: the vascular cambium and the cork cambium.

The vascular cambium is a cylindrical layer of actively dividing cells located between the xylem and phloem. Its activity produces secondary xylem, commonly known as wood, on the inside and secondary phloem on the outside. The accumulation of secondary xylem is the main contributor to the increase in stem thickness. Seasonal variations in the vascular cambium's activity lead to the formation of annual growth rings in many temperate region plants.

The cork cambium, also known as the phellogen, is another lateral meristem that arises in the outer cortex of stems and roots. It produces cork cells (phellem) to the outside and a layer of phelloderm to the inside. These tissues collectively form the periderm, which replaces the epidermis in woody plants, providing protection against mechanical injury, desiccation, and pathogen invasion. The periderm is responsible for the formation of bark.

Sekundærvekst is essential for the structural support and longevity of trees and shrubs, allowing them to grow taller and wider, and to withstand environmental stresses. Non-woody plants, such as herbaceous annuals, typically do not exhibit significant sekundærvekst.