Question

Which plant hormone is related to phototropism?

Answer 1

Auxins

Explanation:

Auxins are plant hormones often found in the meristem (growing) regions of plants. While I'm not too sure of the details, I once read in a book (Grolier: Popular Science Vol. 4) that the presence of auxins in plant tissues promote cell division in plants.

There is a proposed mechanism as to how auxins work in plants to produce phototropism (growing towards light). Consider a sapling growing in a window pane. Scientists believe that auxins are light-sensitive, and generally they tend to gather in the shaded parts of plant.

How does this explain phototropism?

Let's consider the sapling again on the window. Let's say it's left side always receives light from outside while the right side is shaded. As more auxins gather on the right, they promote more cell division in the right side of the stem as opposed to the left. The result is that the plant gets more growth on the right side, causing it to lean to the left and in effect, towards the light.

If you're still confused then try this. Get a matchbox and make it stand upright on the floor. This is your plant. Now , try putting your finger on its bottom right portion(your finger must get in between the matchbox and the floor surface, but do this without tripping the matchbox). What did you observe? The matchbox leaned to the left right? Your finger represents the action of auxins causing more tissue growth on the right, causing the plant/matchbox to lean to the left. A similar principle is involved in the function of auxins in phototropism. Hope this helps.