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How Is Carbon Dioxide Absorbed During Photosynthesis?

During photosynthesis, plants use the sun's energy to convert carbon dioxide into glucose and oxygen. The oxygen is a waste product, but the glucose goes on to be converted into starch, fats, proteins, enzymes and the plant's DNA and RNA. Plants could not produce these molecules without carbon dioxide, and they could not absorb carbon dioxide from the air without the help of specialized cells on and within their leaves.

Stomata
- A plant has tiny openings on the surface of its leaves called stomata or pores. While there are stomata all over a leaf's surface, there are many more on the lower epidermis than on the upper epidermis. The stomata facilitate gas exchange between the plant and the air around it, and they also control water loss. The stomata are controlled by guard cells. Each pair of guard cells can open or close one pore, and the amount of water a plant absorbs and retains is dependent on how wide and how long the stomata remain open.
Mesophyll Tissue
- After absorption, carbon dioxide passes into the internal spaces of the leaf, where it is then diffused into the mesophyll tissue. Two types of mesophyll cells make up the bulk of most dicot leaves. One of them, known as spongy parenchyma, facilitates gas interchange along with the intercellular air spaces and the stomata on the surface. The other, which is called palisade parenchyma or ground parenchyma, is responsible for photosynthesis. This tissue contains the chloroplasts, which convert carbon dioxide into fuel for the growing plant, and which also give the plant its green color.
Calvin Cycle
- The Calvin Cycle is the actual process by which carbon dioxide is converted within the stroma of the chloroplast. It is a series of biochemical, enzyme-mediated reactions in which a chemical within the plant captures six carbon dioxide molecules that have been absorbed. Six carbon atoms from these molecules form the basis of a glucose molecule, which also has six carbon atoms, while oxygen molecules are shed as waste.
Stomatal Closure
- A plant may fail to get enough water or carbon dioxide due to stomatal closure, and consequently lack sufficient raw materials for photosynthesis. Stomatal closure occurs as a reaction to water availability. It can occur reflexively, as water loss causes the guard cells to dry out and close their respective stomata, or it can occur when the environmental potential for water drops below a critical level. Higher temperatures may also cause closure, and wind also triggers the guard cells to close the stomata under some conditions.

Nature