The falling off of leaves of deciduous trees is helpful to the plant because it

Step 1: Analyze the question We're asked why leaf fall (abscission) in deciduous trees benefits the plant. Deciduous trees shed their leaves, usually at the start of the dry season or harmattan.

Step 2: The concept Leaves are the main sites of transpiration, where water vapour escapes through the stomata. In the dry season, the roots find it hard to absorb water from the soil. If the tree kept its broad leaves, it would lose more water than it could absorb and could wilt and die. Shedding leaves is an adaptation that conserves water by cutting down the surface area for transpiration.

Step 3: Evaluate the options

• A. Reduces the rate of transpiration. Correct. With fewer or no leaves, there is far less surface for water loss.
• B. Eliminates excretory products. Leaf fall does remove some wastes stored in old leaves, but this is a minor side effect, not the main benefit. Plants do not shed leaves mainly for excretion.
• C. Bear more fruits. There is no direct link between leaf fall and fruit production.
• D. Mineral salts go only to growing regions. Some nutrients are withdrawn from leaves before they fall, but this is not the main reason for leaf shedding.

Step 4: Answer The main advantage is water conservation through reduced transpiration.

Tip: When you see "deciduous" and "leaf fall", think dry season → water conservation → reduced transpiration. Questions on this topic nearly always point to that link.