How do stems grow?

By The Old House Web

How do stems grow?

Plant stems increase in length and thickness by laying down successive layers of cells much as bricks are laid in building a wall.

Woody stem growth (girth) is the result of cell division in a thin layer of cells called the cambium. The cambium is just under the protective bark layer and becomes active in the spring in response to warm weather. Xylem cells are produced to the inside of the cambium and phloem cells to the outside. The phloem and bark do not accumulate and are sloughed off as the stem increases in diameter. Most of the tissue in a woody stem is accumulated xylem.

Stem length increases as active cells produce new cells at the stem tips. The new cells differentiate into xylem, cambium and phloem. A branch attached to the trunk about 5 feet from the ground increases in thickness and adds length but remains at that height.

What are stem functions?

Stems provide the framework to physically support the leaf canopy and serve as a transport system that connects the roots with the leaves and storage for food manufactured by the leaves. The multi-branching framework, progressing from large limbs to small twigs, exposes the largest possible leaf area to sunlight. The xylem transports water and nutrients up the stem. Sugars manufactured by the leaves are distributed to all growing parts of the plant in the phloem. Stems store surplus food for continued growth during the season and over winter to support spring growth.

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