What Are the Processes by Which Plants Trap the Sun's Energy to Build Carbohydrates? | Home Guides | SF Gate
What Are the Processes by Which Plants Trap the Sun's Energy to Build Carbohydrates?
What Are the Processes by Which Plants Trap the Sun's Energy to Build Carbohydrates?
Plants are among the few known organisms with the ability to manufacture food.
Since plants cannot move about in search of food, they have adapted a means of creating their own food. Through the process of photosynthesis, plants convert sunlight, water and carbon dioxide into a sugar they can either store for the future, or use to satisfy immediate energy needs.
Sunlight and Plant Pigments
Energy is required in order to break down water and carbon dioxide molecules and reassemble them as sugar molecules. Photon particles in sunlight provide that energy source for plants, which absorb these particles with specialized pigments, such as chlorophyll. The exact amount of chlorophyll necessary for photosynthesis varies by species, which is why some plants require full sun while others tolerate shade. Chlorophyll is also what makes plant leaves appear green during the plant’s growing season. Chlorophyll pigments do not readily absorb yellows or greens in sunlight, so those hues are reflected away from the plant.
Add Some Water
Water must also be present in plants for photosynthesis to occur. Water acts as a reducing agent in the chemical process that breaks down carbon dioxide molecules. Water also acts as a transportation means for carrying nutrients and sugars to all parts of the plant. The plant releases much of that water through a process called transpiration. That process creates a siphoning action so that plants can absorb water from the earth through roots. In warmer climates, and during extremely hot days in summer, plants need more water than usual in order to conduct photosynthesis as much more water evaporates into the environment during transpiration.
Carbon Dioxide
Plants absorb carbon dioxide from the air through tiny, specialized cells that create an opening called a stomata. The cells expand or contract to close or open the stomata, allowing the plant to pull in carbon dioxide only when needed. The stomata are located in the epidermis, the outermost tissue layer of leaves. Carbon dioxide exists in the atmosphere as a result of decaying organic matter and the expelled gas from animal respiration. Since plants use this gas in order to make food, they scrub the atmosphere of carbon dioxide, too much of which could harm animal life.
Photosynthesis Process
The exact sequence of chemical reactions occurring in plant leaves during photosynthesis is complex. The ingredients of sunlight photon energy, water and carbon dioxide result in glucose molecules -- a simple sugar or carbohydrate -- that fuels all the activities of the plant. During photosynthesis, the plant combines six water molecules and six carbon dioxide molecules to manufacture one glucose molecule and six oxygen molecules. Some glucose gets absorbed by the leaves during photosynthesis, but much of it gets stored away for overwintering and for new growth in spring. The plant releases oxygen into the atmosphere as a photosynthesis byproduct it does not need.