The light-induced absorbance change around
5 15 nm (aAs15) in chloroplasts has been attributed
mainly to the electrochromic response of pigments
embedded in the thylakoid membranes [ 11. This
change in absorbance, related to the energized state
of the thylakoids, starts with a fast (-IX) rise and
relaxes with a slow (-100 ms) decay [2,3]. Recently,
in intact isolated chloroplasts a biphasic rise, has been
established [4-91. The slow phase of the rise in
aAsl5 has been explained in various ways. The most
common view is that the slow rise of A.4 515is connected with the reduction of cytochrome fand to an
inward translocation of protons [5,8,10].