PHOTOTROPISM

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Plants need to produce their own food with the help of photosynthesis. Sunlight is a key ingredient for photosynthesis. Leaves are basically biological solar panels with a built-in biological mechanism for trapping as much sunlight as possible.

Sometimes certain leaves grow in the opposite direction of sunlight.

This is when the process photo-tropism comes into play.

Photo-tropism is the process by which plants are able to turn towards the direction of sunlight.

Photo-tropism is made up of two words:

PHOTO

Meaning light

TROOPS (Ancient greek word)

Meaning turning

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If the plant or certain parts of a plant receive no sunlight or less sunlight, it won't be able to perform photosynthesis and in turn, food won't be produced for plant growth.

So, photo-tropism is a pretty important process for plants to survive and grow.

The mechanism behind photo-tropism is as follows :

• The plant's tip releases plant hormones known as Auxins. They travel down to the stem, leaves and other various parts of the plant.

• Auxins are responsible for making the plant cells longer. Cells with auxins are longer than the cells without auxins.

• Auxins are accumulated on the darker side of the plant, that is, the part which doesn't receive sunlight or receives very little sunlight.

• Since the part which receives sunlight doesn't face any issue, they don't require these hormones.

As a result, the plant cells on the darker side grow longer and thus the plant grows longer on the darker side. Meanwhile, the brighter side which is receiving sunlight doesn't grow longer.

Due to the difference in length and pressure, the plant bends towards the shorter side, that is, the part which is facing the sun.

Consider the plant to be divided into two equal parts. If one part becomes longer than the other, the pressure on the shorter side will increase and bending would take place.

Due to the secretion of Auxins and the process of Photo-tropism, the leaves which are not receiving sunlight, are able to turn in the direction of sunlight.

Without photo-tropism, all parts of the plant may not receive sufficient sunlight and the plant may die eventually.

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