Basic tree biology and physiology

Basic Tree Biology

Trees are long-lived perennials, mostly woody and branched.
Cellular structure: The main functional cell types in trees are parenchyma (living cells involved in functions such as photosynthesis), collenchyma (provides support), and sclerenchyma (provides additional structural support).
The meristem is the plant tissue responsible for growth. Apical meristem allows elongation (vertical growth), while lateral meristem is responsible for radial growth (width).
Cambium is a type of lateral meristem which generates new transport and support tissues.
Xylem and phloem are cambial tissues responsible for transporting water, minerals, and sugars throughout the tree.
Bark is protective tissue comprising the periderm and phloem, providing a first line of defence against pests and diseases.

Photosynthesis is the process by which trees convert light energy into chemical energy. The reaction uses carbon dioxide and water, producing oxygen and glucose.
Respiration is the process by which trees break down glucose to produce energy, a process that requires oxygen and generates carbon dioxide.
The rate of these two processes varies depending on environmental conditions such as light availability, temperature, and water availability.
If the rate of respiration exceeds the rate of photosynthesis, a tree will use stored energy reserves.

Roots absorb water and nutrients from the soil; the majority happening in the fine, hair-like root structures.
Water is transported from the roots to the leaves through xylem vessels.
Nutrient uptake is aided by symbiotic relationships with mycorrhizal fungi, which extend the root network.

Trees respond to a range of abiotic and biotic stress factors, such as drought, damage, pests and diseases.
Dormancy allows trees to survive periods of adverse conditions, often triggered by environmental cues such as day length and temperature.
Adaptations such as the shedding or changing colour of leaves help to mitigate environmental stress.

Trees grow by adding new cells in the cambium layer, expanding both upwards and outwards.
Wood is primarily composed of xylem tissue, which forms concentric rings known as annual growth rings.
The growth rings indicate the age of the tree and the environmental conditions during each year of growth.

Sexual reproduction in trees involves the production of flowers, followed by pollination and fertilisation.
Fruits and seeds carry and protect the embryo, aiding in dispersal.
Vegetative or asexual reproduction involves the production of new trees from parts of existing ones, such as cuttings or suckers.
Some tree species have adapted to reproduce following disturbance or damage, such as fires or flooding.