Proton release by tea plant (Camellia sinensis L.) roots as affected by nutrient solution concentration and pH

Solution culture experiments were conducted and the protons released were measured with an automatic titration system to determine the main factors affecting proton release by tea roots. Results indicated that the higher were the cation concentrations, the more protons were released from the roots, suggesting that tea roots took up a large amount of cations during growth, and then released protons to maintain charge balance of the plant body. The amount of protons released from tea roots at controlled pH was much higher than that in the treatments with uncontrolled pH. Stepwise multiple linear regression analysis showed that both NH4+ and Al(III) played distinct roles in proton release by tea plant roots. The uptake of Al(III) and NH4+ and subsequent release of protons may be an important mechanism for soil acidification in tea gardens.