Atmospheric CO₂ has been increasing rapidly since the late 1800s, largely due to human activities. Recall that CO₂ enters leaves through stomata and can then be used for photosynthesis. However, transpiration occurs as a result of water evaporating through stomata.
How have plants responded to elevated CO₂ levels?
What impact, if any, do you predict elevated CO₂ levels will have on the number of stomata in leaves and on the transpiration rate?

Verified step by step guidance

1. Understand the role of stomata: Stomata are small openings on the surface of leaves that allow for gas exchange. They are crucial for photosynthesis as they let CO2 enter the leaf, but they also allow water vapor to escape, which is known as transpiration.
2. Consider the effect of elevated CO2 levels: With increased atmospheric CO2, plants can potentially absorb more CO2 for photosynthesis. This might lead to changes in the number of stomata as plants adapt to the new conditions.
3. Predict changes in stomatal density: Research suggests that elevated CO2 levels can lead to a decrease in stomatal density. This is because plants may not need as many stomata to absorb the necessary CO2, reducing water loss through transpiration.
4. Analyze the impact on transpiration rate: With fewer stomata, the rate of transpiration may decrease. This is beneficial for plants as it helps conserve water, especially in environments where water is limited.
5. Consider the overall plant response: Plants may exhibit a range of responses to elevated CO2, including changes in growth patterns, photosynthetic efficiency, and water use efficiency. These adaptations help plants optimize their survival and growth in changing environmental conditions.

Key Concepts

Photosynthesis

Photosynthesis is the process by which plants convert light energy into chemical energy, using carbon dioxide and water to produce glucose and oxygen. Elevated CO2 levels can enhance photosynthesis, as more CO2 is available for the Calvin cycle, potentially increasing plant growth and productivity.

Stomata

Stomata are small openings on the surface of leaves that allow for gas exchange, including the intake of CO2 for photosynthesis and the release of oxygen. They also facilitate transpiration, the process of water vapor loss. Changes in CO2 levels can influence stomatal density and behavior, affecting both photosynthesis and transpiration rates.

Transpiration

Transpiration is the process by which water evaporates from plant leaves through stomata, helping to cool the plant and drive nutrient uptake. Elevated CO2 levels may lead to reduced stomatal density, potentially decreasing transpiration rates, as plants optimize water use efficiency in response to increased CO2 availability.