Plants inhale carbon dioxide and exhale oxygen through tiny closable holes normally found on the underside of leaves. These holes are called stomata (singular stoma).
Stomata control water flow
One really amazing aspect of stoma behavior is how they control water flow within a plant. Chemically, water will always move from areas of high humidity to areas to low humidity. When a stoma opens, it creates a bubble of high humidity. This exhaled moisture evaporates or is pulled away. Due to surface tension, more water is pulled out of the plant. This action works its way down to the roots, which then pulls water from the soil! This is how plants absorb water from the ground!
I hope this information inspires you to grow more of your own food. You can ask your garden questions on my Home page.