Plant Hormones (phototropism, geotropism) pt2

how does a stem grow

positive phototropism, negative geotropism

how do roots grow

negative phototropism, positive geotropism

phototropism

growing towards light

geotropism

growing towards gravity

how does positive phototropism work

auxin diffuses to the shaded side of the stem, stimulating cell growth, so the shaded cells elongate and grow longer whilst the sunny cells grow at a normal rate which causes the stem to bend towards the light

how does negative phototropism

auxin diffuses to the shaded side of the root, causing cells to grow slower than the ones exposes to light, causing the root to bend away from light

how does positive geotropism

auxin accumulates at the bottom side of the roots due to gravity which means the bottom grows at a slower rate than the top, causing the root to bend downwards

how does negative geotropism

auxin accumulates at the bottom of the stem due to gravity which promotes the cells to grow faster, elongating an growing larger whilst the bottom side grow slower causing the stem to bend upwards