DENDROLOGY

Detailed explanation-1: -Positive gravitropism occurs when roots grow into soil because they grow in the direction of gravity while negative gravitropism occurs when shoots grow up toward sunlight in the opposite direction of gravity.

Detailed explanation-2: -Plant parts can grow with or against gravity. This type of tropism is called gravitropism. Roots of a plant grow downward and exhibit positive gravitropism. Stems, on the other hand, exhibit negative gravitropism since they grow upwards and against the force of gravity (see Figure 1).

Detailed explanation-3: -The correct answer is: geotropism. The response or the movement of the plant parts towards the force of gravity is called geotropism. The downward growth of roots towards the pull of gravity is called positive geotropism.