Plants coordinate their growth in response to environmental cues. Apart from light and gravity, name one environmental stimulus that can trigger a directional growth response (tropism) in plants, and state the term used to describe this specific tropism.

Plan a laboratory investigation to determine the effect of unilateral light on the direction of growth of germinating plant shoots.

Include details of the control setups needed to confirm that the response is due specifically to unilateral light rather than other environmental factors.

You may suggest using standard laboratory equipment, such as cardboard boxes with a side window, Petri dishes, young cereal seedlings, damp filter paper, and a rotating clinostat.

Explain how positive phototropism in a plant shoot helps the plant to survive.