BIOMOLECULES AND ENZYMES

Detailed explanation-1: -The effect of gravity on the direction of plant growth is called gravitropism. (The effect of gravity on plant growth is often called geotropism because the Earth itself (geo) is responsible for the stimulus.

Detailed explanation-2: -Just like phototropism, geotropism is also caused by an unequal distribution of auxin. In a root placed horizontally, the bottom side contains more auxin and grows less-causing the root to grow in the direction of the force of gravity.

Detailed explanation-3: -What do roots need? Roots are dynamic and their growth is strongly affected by the environmental conditions found in the root zone. To survive and grow, they need Air (gas exchange), Water, Non-limiting Temperature, Carbohydrates, Minerals, Space, Low Soil Density, Microbial Associations and Non-toxic soil chemistry.

Detailed explanation-4: -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-5: -It is essential for roots to grow down so they can explore the soil and maximise their water uptake.