Britannica Sources used in this answer

How do light intensity and temperature affect the rate of photosynthesis?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Diagram of a tree leaf illustrating photosynthesis, with arrows showing sunlight, water, and carbon dioxide entering the leaf and sugars and oxygen being produced. A person is shown beside the tree to demonstrate the exchange of oxygen and carbon dioxide between plants and animals. — Photosynthesis Diagram of photosynthesis showing how water, light, and carbon dioxide are absorbed by a plant to produce oxygen, sugars, and more carbon dioxide.

Light intensity and temperature are critical environmental factors that regulate the rate of photosynthesis.

Light Intensity

At low to medium light intensities, the rate of photosynthesis increases proportionally with light intensity, as the process is driven by photochemical reactions. However, as intensity continues to rise, the rate eventually reaches a point of "light saturation," where it no longer increases because other factors, such as the enzymatic reactions of the dark stage, become rate-limiting. The compensation point represents the specific intensity where the rate of carbon dioxide uptake in photosynthesis exactly balances the rate of carbon dioxide release through respiration.12

Temperature

Temperature influences the enzymatic stages of photosynthesis. While reaction rates generally increase with temperature, enzymes function efficiently only within a specific range; extreme heat can cause denaturation, destroying enzyme activity. Furthermore, rising temperatures increase photorespiration, a process that competes with photosynthesis and limits its overall rate, particularly in land plants when water is scarce.314