Facts about Phototropism
Some roots of green plants, such as Allium sativum (garlic), also have exhibited positive phototropism (Jost 1907).
Most plant shoots exhibit positive phototropism, while roots usually exhibit negative phototropism, although gravitropism may play a larger role in root behavior and growth.
Positive phototropism is common among the shoots of higher plants, while roots usually exhibit negative phototropism.
Growth or movement towards a light source is a positive phototropism, while growth away from a light source is called negative phototropism.
Both root tips and most stem tips exhibit positive phototropism to red light.
Some vine shoot tips exhibit negative phototropism, which allows them to grow towards dark, solid objects and climb them.
Each organism, or part of an organism, can have one of three conditions with respect to light: towards a light source (positive phototropism), away from a light source (negative phototropism), or indifference (Jost 1907).