Factors Affecting Plant Growth

Applied Science: BTEC Level 3 National Extended Diploma, topic 3.5.1

A variety of different factors can impact plant growth and distribution:

Human activity can impact plant distribution.
For example, the trampling of small plants and young tree shoots can limit plant growth.
This is particularly true in woodlands with multiple walking paths.
Other human effects may be pollution, felling, and introduction of new plant species.

Most plants grown in a pH range of 5-7. Some require acidic or alkaline soils.
For example, rhododendrons only grow in acidic soil.
Factors that affect soil pH include acid raid, uses of fertilizers, and weathering of rocks.
Some plants need adaptions to grow in soils with low aeration.
For example, rice plant roots grow completely submerged in water.
Rice plants contain a spongy tissue called aerenchyma that allows low-resistance gas exchange between the above water and submerged parts of the plant.

Plants need light for photosynthesis.
Increasing light intensity increases the rate of photosynthesis because more energy is provided.
Tall plants create a lot of shade. As a result, some plants have developed shade tolerance.
This means they are adapted to grow at lower levels of light intensity and can grow in the shade of larger plants.
Plants the grow in direct light also need adaptions to high light intensity to prevent drying out.
These adaptions include UV-absorbing pigments and waxy cuticles.

Temperature plays an important role in the rate of photosynthesis.
Rate of photosynthesis increases up to the optimum temperature (about 45°C). Above this temperature, the rate starts to fall.
At too high temperatures, enzymes in the plant denature. This means photosynthesis can no longer occur and the plant dies.
If temperatures are too low, plants will not be able to grow as the rate of photosynthesis will be to low.

Plants need water for photosynthesis.
Most plants tend to require moist soils and regular rainfall to grow successfully.
Plants that grow climates with little water availability are called xerophytes. They need adaptions such as waxy cuticles and leaves with a small surface area.
These adaptions help prevent excess water loss.
Cacti are examples of xerophytes.

Plants need different minerals for growth.
For example, plants need nitrates to build proteins, magnesium ions to make chlorophyll, and phosphorus to make DNA.
Soils with low mineral ion concentrations can be enhanced with fertilizers.
Some plants are also adapted to grow in soils with low mineral ion concentrations.
For example, leguminous plants contain root nodules that convert nitrogen gas in air into nitrates the plant can use for growth.

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