Sekundaariruiskutusjärjestelmä

Sekundaariruis is a Finnish term that translates to "secondary growth" in English. It refers to the increase in diameter of stems and roots in plants. This process is primarily responsible for the formation of wood and bark in woody plants like trees and shrubs. Secondary growth is a crucial adaptation for these plants, providing structural support and allowing for more efficient transport of water and nutrients throughout the organism.

The process of secondary growth occurs due to the activity of two lateral meristems: the vascular cambium and the cork cambium. The vascular cambium is a layer of actively dividing cells located between the xylem and phloem. It produces secondary xylem (wood) towards the inside of the stem or root and secondary phloem towards the outside. The cork cambium, typically found in the outer bark, produces cork cells, which replace the epidermis and provide a protective outer layer.

In temperate regions, the seasonal activity of the vascular cambium leads to the formation of annual growth rings in wood. These rings, visible as alternating lighter and darker bands, reflect variations in growth rates between spring and summer. The width and characteristics of these rings can provide valuable information about a tree's age and the environmental conditions it experienced during its lifetime, a field of study known as dendrochronology. Secondary growth is absent in most herbaceous plants, which rely on primary growth for their development.