DENDROLOGY

Detailed explanation-1: -Root growth shows characteristic tropisms including positive geotropism (growth in the direction of gravity, also described as positive gravitropism) and avoidance of obstacles (sometimes described as negative thigmotropism).

Detailed explanation-2: -The roots grown downward in the direction of gravity, which is positive gravitropism, and the shoot grows upward away from gravity, which is negative gravitropism. The reason plants know which way to grow in response to gravity is due to amyloplasts in the plants.

Detailed explanation-3: -Negative vs. Positive gravitropism is a plant’s positive response to the gravitational source of Earth’s center mass. This contrasts with a negative gravitropism, which is a plant’s negative response to the same source of gravity.