Basic Tree Biology

Tree Cells and Tissues

Cells are the building blocks of a tree; they divide and grow to create different tissues.
Xylem transports water and nutrients from the roots to the leaves; comprised of uniquely shaped cells that form long tubes.
Phloem carries sugars (formed by photosynthesis in the leaves) to the rest of the tree; comprised of living cells.
Cambium layer is responsible for thickening the tree’s trunk and branches; it divides to produce new xylem and phloem cells.
Parenchyma cells storage tissues holding reserves of water, nutrients and sugars; These cells are found in the roots, stems, leaves, and fruits.

Photosynthesis is the process by which green plants and trees make food using sunlight.
The equation for photosynthesis is 6CO2 + 6H2O (+ light energy) –> C6H12O6 + 6O2.
Respiration is the process where trees convert glucose (produced during photosynthesis) and oxygen into energy, creating CO2 and H2O as byproducts.
Respiration continues day and night, while photosynthesis only occurs during daylight with sufficient sunlight.

A tree is made up of three basic parts: the crown (leaves and branches), the stem (or trunk), and the roots.
The crown is where photosynthesis takes place in the leaves and where the tree’s energy is produced.
The trunk provides stability, transports water, nutrients and sugars between the roots and leaves, and store reserves.
Roots absorb water and minerals from the soil, anchor the tree, store food reserves, and are involved in hormones production.

Trees have a specific growth pattern known as determinate growth; each year, they grow a new layer of wood, seen as tree rings.
Tree growth occurs in the growing shoots and roots tips known as meristems.
Growth regulators or hormones control different aspects of growth and development; for example, auxins promote cell elongation.

Trees can reproduce either sexually (via seeds) or asexually (vegetative reproduction such as budding).
Seeds form after pollen fertilises an ovule; seeds are spread through various methods like wind, water or animals.
Propagation is when parts of a tree grow into a new tree — for example, a cutting, a bulb or a root section.

Trees can suffer from stress due to factors like poor soil, lack of water, temperature extremes, pests, and diseases.
Defence mechanisms include physical barriers (bark), chemical defences (toxic or bad-tasting substances), compartmentalisation (isolating damaged or infected areas).
Monitoring trees regularly, proper pruning, and providing correct nutrition helps to maintain a tree’s health.