What causes a green plant exposed to the light on only one side, to bend toward the source of light as it grows ?
Light stimulates plant cells on the lighted side to grow faster.
Auxin accumulates on the shaded side, stimulating greater cell elongation there.
Green plants need light to perform photosynthesis.
Green plants seek light because they are phototropic.
Auxin accumulates on the shaded side, stimulating greater cell elongation there. This typically causes the positive phototropism.