Fig. 3.

Photosystem I megacomplex induction increases with growth light intensity and leaf age and is correlated with high Photosystem I/II ratios. Growth light intensity dependence of PSI megacomplex induction. Spinach plants were grown under either, a moderate (150 µE/m²/s) or b high (600 µE/m²/s) light conditions and the first sets of mature fully expanded leaves were processed for green gel electrophoresis. Dark to Light: leaves were sampled after overnight darkness (0) and 15 and 30 min after the lights were turned on. Light to High Light: Leaves were sampled midday under growth light and after 15 and 30 min of high light treatment. High light treatments were double normal growth light intensity. c Interplay between leaf age and growth light intensity on PSI-MC induction. Spinach plants were grown under moderate or high light conditions as in panel a. Leaves were grouped into unexpanded (young), fully expanded (mature), or visibly yellowing (old). Leaves of plants grown under high light conditions senesced earlier, so similar leaves were used for comparison rather than identical cohorts. d Western blotting of samples derived from green gel shown in panel c. A portion of the same solubilized thylakoid samples which had been loaded onto the green gel were denatured in Laemmli buffer and run on standard SDS-PAGE for Western blotting. Samples were loaded on an equal chlorophyll basis