Lumen alkalization under elevated bicarbonate concentration outside isolated thylakoids of higher plants.

Elevated bicarbonate concentration increases lumen pH and stimulates electron transport in isolated pea thylakoids, indicating bicarbonate as a potential regulator of thylakoid luminal pH.

• Why it matters: Understanding how stromal bicarbonate influences thylakoid lumen pH is crucial for revealing mechanisms regulating photosynthesis, which remains unclear despite its importance in plant biology.
• What they did: Researchers increased bicarbonate levels in isolated pea thylakoids and observed that it raised luminal pH and stimulated electron transport, especially in photosystem I, using 2,6-dichlorophenolindophenol as a pH-sensitive electron donor.
• The result: Findings suggest bicarbonate affects luminal pH via stimulating proton efflux through ATP-synthase and transporting bicarbonate into the lumen, offering new insights into pH-dependent photosynthetic regulation.