Answer:
Root hair cells are alive and therefore need energy, which is why root hair cells contain many mitochondria in them. Root hair cells don't contain chloroplasts. Chloroplasts are used by the plant to make food using light energy. Since the roots aren't exposed to any form of light, they have no need for chloroplasts.
Heliotropism is the process that describes how a plant specifically tracks the sun's movement across the sky.
