English: Metabolism of C₃ plants: During the day, plants convert light energy to chemical energy via photosynthesis. This requires CO₂, which is taken up via stomata (small openings in the leaves), and water, which is taken up by the roots. The uptake of CO₂ from the stomata inevitably results in the diffusion of water (transpiration). The carbon reactions of photosynthesis (Calvin/CBB cycle) yield triose phosphates (GAP) that can either be used for sucrose synthesis or the synthesis of starch (via glucose). Starch functions as an energy storage in chloroplasts. Sugars, such as sucrose, can be used for cellular respiration during daytime. In the absence of light, the stomata are mostly closed, and plants convert storage carbohydrates (e. g., starch) to glucose. Glucose is then metabolized during cellular respiration to synthesize ATP and for biosynthesis of cellulose, proteins, lipids etc. Note: TCA cycle = tricarboxylic acid cycle (=Krebs/citric acid cycle); OXPHOS = oxidative phosphorylation system