Advanced Placement (AP) Biology Practice Exam

What is the primary function of stomata in plants?

1. Photosynthesis regulation

2. Water retention

3. Gas exchange regulation

4. Nutrient absorption

The correct answer is: Gas exchange regulation

The primary function of stomata in plants is to regulate gas exchange. Stomata are small openings found on the surfaces of leaves and stems that allow for the exchange of gases between the plant and its environment. This regulation is crucial because it facilitates the intake of carbon dioxide needed for photosynthesis, while also enabling the release of oxygen as a byproduct of this process. Additionally, stomata play a role in transpiration, the process by which water vapor exits the plant. By opening and closing, stomata can control water loss, leading to the relationship between gas exchange and water regulation. However, their main role centers around the exchange of gases, highlighting their importance in supporting photosynthesis and overall plant health. While stomata do influence water retention, that is not their primary function; rather, they are more directly involved in managing the exchange of gases. Nutrient absorption occurs through the roots of the plant, not through the stomata, and while stomata can impact the regulation of photosynthesis by allowing carbon dioxide in and oxygen out, this aspect is a component of the broader function of gas exchange.