2.81) Positive Phototropism

Positive phototropism = the growth towards the light

• Let's say we're given a tip of a stem. The direction in which the stem would grow toward depends on which side the light was shone on.
• For example, the light was shone from directly above the stem. The stem would then grow upward towards the light.
• If the light was shone only on the right side of the stem, then the stem would grow right towards the light.
• This happens because of a plant hormone called auxin. Auxin builds up on the side of stem with lesser light intensity, causing it to bend toward the opposite side (the side with greater light intensity).