A Level Biology Practice Exam

What is the primary function of stomata in plants?

1. Pores that allow water retention

2. Structures that provide structural support

3. Pores that allow gaseous exchange

4. Cells that absorb sunlight

The correct answer is: Pores that allow gaseous exchange

The primary function of stomata in plants is to facilitate gaseous exchange. Stomata are small openings found primarily on the surfaces of leaves, and they play a crucial role in the exchange of gases between the internal tissues of the plant and the external environment. Through these pores, carbon dioxide enters the plant for photosynthesis while oxygen, a byproduct of this process, is released into the atmosphere. Additionally, stomata also regulate water loss through transpiration, which is vital for maintaining plant hydration and nutrient transport. Understanding the role of stomata in gas exchange is crucial because it highlights their importance in both photosynthesis and respiration, processes that are essential for the growth and survival of the plant. In contrast, the other choices refer to functions that are not directly related to stomata. For instance, stomata do not mainly serve to provide structural support or solely absorb sunlight, as structural support is primarily provided by the plant's vascular system and cell walls, while sunlight absorption occurs during photosynthesis mostly through chlorophyll in the leaves. Water retention is also not their primary function, as while stomata do influence water loss, their main role revolves around the exchange of gases.