Table II.

PSII activity and the Mn content of thylakoid membranes isolated from wild-type, ΔPsbP, and ΔPsbQ tobacco plants

Data presented are mean ± sd of three measurements.

Wild TypeΔPsbPΔPsbQ
O2 evolutiona (μmol O2 [mg chl]−1 h−1)241 ± 1026 ± 3242 ± 12
+5 mm CaCl2b245 ± 1553 ± 3240 ± 9
Mn (ng [mg chl]−1)c0.66 ± 0.040.44 ± 0.010.64 ± 0.03
  • a The buffer for measurement was 50 mm HEPES/NaOH, pH 7.6, containing 0.4 m Suc, 10 mm NaCl, 5 mm MgCl2, and 5 mm NH4Cl. As electron acceptors for PSII, 0.5 mm K3Fe(CN)6 and 0.5 mm p-phenylbenzoquinone were used.

  • b Five millimolar CaCl2 was added to the buffer for measurements instead of 10 mm NaCl.

  • c The Mn content was determined using an atomic absorption spectrophotometer.