Florida Biology EOC Practice Test 2025 - Free Biology End-of-Course Practice Questions and Study Guide

The stomata are small openings located primarily on the surface of leaves that play a crucial role in controlling the rate of transpiration in plants. Transpiration is the process by which water vapor is lost from the plant to the atmosphere, primarily through these openings. The stomata can open and close in response to environmental conditions (such as light and humidity) and the plant's internal needs (such as water availability).

When the stomata are open, water vapor can exit the leaf, leading to transpiration, which also helps with nutrient uptake and cooling the plant. Conversely, if the plant is experiencing water stress, the stomata can close to minimize water loss. Therefore, the stomatal control is essential for maintaining the plant's water balance and ensuring efficiency in transpiration.

In contrast, roots are primarily responsible for water and nutrient uptake from the soil, leaves serve as the site for photosynthesis and have stomata on their surfaces, and phloem is involved in the transport of sugars and organic molecules throughout the plant. These functions are important but do not directly control transpiration rates like the stomata do.