RELATION OF MEMBRANE STRUCTURAL CHANGES TO ENERGY SPILLOVER IN OAT AND SPINACH CHLOROPLASTS: USE OF FLUORESCENCE PROBES AND L IGHT SCATTERING

cations on energy spillover between Photosystems I and II, as indicated by chloro-phyll a fluorescence, was confirmed in spinach. Significant differences with oats, peas and lettuce were found using the same low salt method of preparation: the response to Na + and Ca 2+ was reversible, Ca 2 ÷ alone, when added first, produced a large (85 %) increase in the variable portion of the chlorophyll a fluorescence transient or the steady-state fluorescence, and Ca 2 + not only fully restored a Na ÷ induced inhibi-tion of 680 nm fluorescence, but brought it above the original evel. The fluorescence probes 1-anilinonaphthalene-8-sulfonate and N-phenyl-l-naphthylamine showed a rapid and a slower response, respectively, to the addition of mono- or divalent cations. Neither the structural changes responsible for the probe data, nor those leading to the measured cation stimulated changes in 90 ° light scattering could be precisely equated with any alteration of conformation i volved in the chlorophyll spillover events