What causes a green plant to bend towards light as it grows?
a. Because green plants need light to carry on photosynthesis
b. Because green plants are phototropic
c. Light stimulates plants cells on the lighted side to grow faster
d. Auxin accumulates on shaded side stimulating greater cell elongation

Hint: We normally have potted plants in our house. If you have, you might observe the plant growing upward. In other words, we can say that the plant is growing towards the light. However, it has a reason to move in the direction of the light. This phenomenon is called phototropism.

Complete answer:
The plant hormone that plays an important role in phototropism is called Auxin. It is said that less amount of auxin is transported towards the illuminated side. This is why the plant produces more on the dappled side and bends in the direction of the light source. It promotes cell elongation.

The chlorophyll present in the plant gets refilled from time to time due to which the green plants became phototrophic. They can prepare their own food due to the existence of this green pigment.

The light helps the plant in the process of photosynthesis. However, it is not capable of stimulating plant cells on the lighted side to grow faster.

It is a fact that green plants need light to carry on the process of photosynthesis. However, it has no relationship with the growth of the plant.

Hence, the correct answer is option (D).

Note: Auxin is a plant hormone. The hormone auxin controls the growing movement in response to light. It also promotes the elongation of the cell. It is said that this hormone is distributed unequally in the plant cells. We can say that this hormone is transported towards the shady side and thus present in higher concentration.