Doug plants a few peas. After two days, he sees the shoot and the root forming. He observes that the shoot grows upward, toward the light. The root grows downward, into the soil. Why do these embryonic organs grow in a specific direction?

The roots of the plant show positive gravitropism and negative phototropism. The shoots exhibit positive phototropism and negative gravitropism. Roots grow in the direction where gravity is but also grown against the light. Growth of shoots are opposite with the roots.