Definition of Photosynthesis
Photosynthesis is the biochemical process by which green plants, algae, and some bacteria convert light energy from the sun into chemical energy stored in glucose. Using chlorophyll in chloroplasts, plants absorb sunlight, water from the soil, and carbon dioxide from the air to produce glucose as a food source and release oxygen as a byproduct. The overall equation is 6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂.
Key Stages of Photosynthesis
Photosynthesis occurs in two main stages: the light-dependent reactions and the light-independent reactions (Calvin cycle). In the light-dependent phase, chlorophyll captures sunlight to split water molecules, generating ATP and NADPH while releasing oxygen. The light-independent phase uses these energy carriers to fix carbon dioxide into glucose through a series of enzyme-driven reactions in the stroma of chloroplasts.
Practical Example in a Plant
Consider a young sunflower seedling. During the day, its leaves capture sunlight, drawing water through roots and carbon dioxide via stomata. This process synthesizes glucose, which the plant uses to build stems, leaves, and flowers. As a result, the seedling grows taller and develops a robust structure, demonstrating how photosynthesis directly fuels biomass accumulation and overall development.
Importance for Plant Growth and Ecosystems
Photosynthesis is essential for plant growth as it provides the primary energy source for cellular processes, enabling the synthesis of proteins, lipids, and other compounds needed for tissue expansion and reproduction. Beyond plants, it sustains ecosystems by producing oxygen for respiration and forming the base of food chains, supporting herbivores and ultimately all life forms while regulating atmospheric carbon levels.