Functional antenna size of PSII and PSI measured in wild-type and mutants TAM-2 and TAM-4. (a) Variable Chl fluorescence was induced with a green light of 15 μmol photons m-2 s-1, on dark-adapted cells (about 1.0 • 107 cells/ml) in BG-11 medium supplemented with 50 μM DCMU. The reciprocal of time corresponding to two-thirds of the fluorescence rise (T2/3) was taken as a measure of the PSII functional antenna size. (b) The kinetics of P700 oxidation (ΔAbs at 705 nm) were measured on thylakoid suspension (75 μg Chl/ml) treated with 50 μM 2,5-dibromo-3-methyl-6-isopropylbenzoquinone (DBMIB) and 1 mM methylviologen, upon illumination with a 10-s pulse of red actinic light (λ =630 nm, 560 μmol photons m-2 s-1). Data are expressed as mean ± SD, n =7.