Root plasma membrane H+-ATPase is involved in low pH-inhibited nitrogen accumulation in tea plants (Camellia sinensis L.)

Abstract

Tea is a perennial leaf crop and grows in acidic soil with a pH usually ranging from 4.0 to 5.0. Tea leaves are rich in free amino acids that are strongly associated with nitrogen accumulation. Previous studies mainly have focused on NH4+ nutrition on tea growth and development; however, studies of the impact of NO3− nutrition on tea root plasma membrane (PM) H+-ATPase activities are limited. In our study, tea plants (cv. Shu chazao) were grown using NO3− as the nitrogen (N) source at pH 4.0 and 5.0. We found that compared with tea plants grown at pH 5.0, significantly lower N accumulation was found in tea plants grown at pH 4.0. Also, more depolarized PM potentials, and a lower net H+ fluxes, PM H+-ATPase activities, Km, Vmax and PM H+-ATPase protein levels were found at pH 4.0 than at pH 5.0. Furthermore, the PM H+-ATPase inhibitor, vanadate, significantly reduced nitrogen accumulation in tea roots and plants at pH 4.0 and 5.0, further confirming the role of PM H+-ATPase in nitrogen accumulation in tea plants. Exogenously applied ATP induced increased PM H+-ATPase activity in tea roots at both pH 4.0 and 5.0. Low pH impaired root respiration and decreased ATP concentration in tea roots grown under nitrate nutrient. Taken together, our results suggest PM H+-ATPase is involved in the lower accumulation of N in tea roots cultivated in nitrate nutrient at pH 4.0 than 5.0, and this is related to lower respiration rate and ATP concentrations.