quizlwt Select all that are true regarding gas exchange in a vascular plant. Guard cells regulate whether stomata are open or closed based on availability of water in the plant. Guard cells regulate whether stomata are open or closed based on availability of water in the plant. When stomata are closed, the plant is not able to exchange oxygen and carbon dioxide gas with the atmosphere. When stomata are closed, the plant is not able to exchange oxygen and carbon dioxide gas with the atmosphere. Stomata are open when a plant is low on water, and closed when a plant has plenty of water. Stomata are open when a plant is low on water, and closed when a plant has plenty of water. Plants close their stomata to reduce water loss. Plants close their stomata to reduce water loss. Guard cells regulate whether stomata are open or closed based on availability of sugars in the plant. Guard cells regulate whether stomata are open or closed based on availability of sugars in the plant. Transpiration is loss of water vapor from leaves. Transpiration is loss of water vapor from leaves. Skip to navigation