Photosynthesis vs Respiration Balance
Plants are constantly juggling two processes - photosynthesis and respiration - and the balance between them changes throughout the day. Using bicarbonate indicator, scientists can track CO₂ levels: purple means less CO₂, red is normal, and yellow shows increased CO₂.
In bright light, photosynthesis dominates, using up CO₂ and turning the indicator purple. Cover the plant with foil, and only respiration occurs, producing CO₂ and turning the indicator yellow. Partial shading creates a perfect balance where both processes occur at equal rates.
The compensation point is fascinating - it's when photosynthesis and respiration rates are exactly equal, so there's no net exchange of gases with the atmosphere. This happens twice daily, at sunrise and sunset, as light levels change.
Think About It: At night, plants actually consume oxygen and release CO₂, just like animals do through respiration alone.
Daily Gas Exchange Patterns
Throughout a 24-hour cycle, plants show predictable patterns of gas exchange. At night, only respiration occurs, so plants take in oxygen and release carbon dioxide. As dawn breaks, photosynthesis begins while respiration continues, creating a complex balance.
By noon, photosynthesis reaches its maximum rate due to intense sunlight, while respiration continues steadily. The plant now takes in much more CO₂ than it releases, and produces more oxygen than it consumes. This is when plants are working hardest to feed themselves and supply our atmosphere with oxygen.
As sunset approaches, photosynthesis slows down due to decreasing light intensity until the second compensation point is reached. Then the cycle begins again, demonstrating the beautiful rhythm of plant life.