Describe how different environmental factors affect the direction of root and shoot growth in plants. You should refer to the role of plant hormones.

You could refer to the following. Shoots grow upwards towards light (positive phototropism) and grow against the force of gravity (negative gravitropism). Roots grow with the direction of gravity (positive gravitropism) and towards moisture (positive hydrotropism). Auxin can be used as an example hormone. Auxin stimulates growth. Unequal distribution of auxin in the stem or root causes unequal growth. This allows directional growth. If auxin builds up on the right side of the stem, this side will grow at a faster right and the stem will bend to the left.