What causes a green plant exposed to the light on only one side, to bend toward the source of light as it grows?
(a) Green plants need light to perform photosynthesis
(b) Green plants seek light because they are phototropic
(c) Light stimulates plant cells on the lighted side to grow faster
(d) Auxin accumulates on the shaded side, stimulating greater cell elongation there
(d) When a green plant exposed to light (phototropism) on one side, which makes it bend towards the source of light is due to the effect of auxins. Auxin accumulates on the shaded side due to which it stimulates cell elongation and enlargement. Its movement is polar and passes from shoot tip to region of elongation. It helps in elongation of both roots and shoots. Auxin (indole 3-acetic acid) also produces tropical responses like phototropism and geotropism.