Essential requirements for plant growth

The major requirements for plant growth in the early stages are air, water and warmth.  Later, the plant needs light, carbon dioxide and plant nutrients as well.

The plant needs air.

A plant is a living thing and needs to respire (or breathe) in the same way that an animal does. As it grows, it requires more and more oxygen.  There must be sufficient air in the soil or the plant will die.  Soil that is waterlogged has no air so a seed will not germinate, but will rot.

The plant needs water. Water is an essential part of the tiny cells in each plant.

Water is taken up via the root hairs moving through the plant until it eventually evaporates through the leaves in very large quantities by a process known as transpiration. In passing through the plant, the water carries plant nutrients from the roots to various parts of the plant.  It also distributes the products of photosynthesis in the leaves.  For every ton of dry matter produced by a plant, about 200 tons of water has to be transpired.

The plant needs warmth or temperature.

A seed will only germinate if the temperature is right. This is usually between 10-45 degrees centigrade, although some seeds need higher temperatures.  The plant will only grow if the temperature is over 6 degrees C.  Cold, frosty conditions can seriously damage plant growth.  Extremely hot conditions 40 degrees C plus can cause stress to a plant particularly with a hot dry wind.  Certain vegetable crops will only grow in cooler times of the year in some tropical countries.  Conversely, if planting wheat, you need the frost to germinate the seed initially.

The plant needs carbon dioxide.

Plants have the ability to make food out for their leaves by a process known as photosynthesis.  This is a unique feature of plants as the energy is stored.  Light coming from the sun’s rays acts on the chlorophyll in the leaves and enables the water and carbon dioxide to react chemically, giving the resulting products of sugar (stored energy) and oxygen (given off in the atmosphere).

Put as an equation:-

Carbon Dioxide + Water + Energy = carbohydrates + oxygen

The plant needs light.

Light is the energy source for the plant. The amount of photosynthesis the plant can do is partly due to the length of available daylight and partly to the light intensity of the sunlight.

Length of daylight and darkness is linked to the distance from the equator. Nigeria for example is on the equator so the daylight and night periods are equal all year round with very rapid sunsets and sunrises. Most of the tropics do have very high light intensity with long hours of sunshine, thus high potential for photosynthesis.

The plant requires nutrients.

Many chemical substances are needed for a plant to grow.  The chemicals required in larger quantities are called major nutrients; the chemicals required in smaller quantities are called minor nutrients or trace elements.

The major nutrients are carbon, hydrogen, nitrogen, phosphorus (phosphate), potassium (potash), calcium, magnesium and sulphur.

Among the trace elements are boron, manganese, copper, iron and zinc.

Deficiency diseases can be recognized by an expert from visual inspection of leaf discoloration, but experience is needed to distinguish between deficiency symptoms and the effects of other problems such as damage by insects or poor drainage.

If the above can be achieved, then the crop will flourish.

Written by Fiona Johnson

October 2011


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