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Question 6
How does phototropism occur in plants?


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Solution

Now we know that phototropism is a movement exhibited by plants as a positive response to sunlight. A plant which otherwise is not capable of locomotion, responds to sunlight by bending towards it, as solar energy is vital to photosynthesis in plants. In this effort of tropic movement, the plant is ably helped by the hormone that helps the cells to elongate that is Auxin. Auxin is evenly distributed all around the plant stem for regular growth of the stem. However, when the plant requires moving to its right let us say, the auxins move en masse from the right side of the stem to its left side, thus accelerating cells in the stem to grow faster on its left side than its right side. Clearly, a mismatch in terms of growth of the cells happens here where the left side of the stem becomes longer in length than its right side, making the stem bend towards the right side. The opposite happens when the plant bends to the left. This is how phototropism occurs in plants.

Environmental triggers such as sunlight (visible frequency) will change the directions of the growth of plant parts. These directional, or tropic, movements can be either towards the stimulus or away from it. So, in two different kinds of phototropic movement, shoots respond by bending towards light while roots respond by bending away from it.


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