The pioneering work of Robert Emerson and
coworkers, beginning in 1957 with the discovery of
the Enhancement effect, and the crucial experiments
of Bessel Kok, Louis N.M. Duysens and Jan Amesz in
1961 on the antagonistic effect of ‘light 1’ and ‘light
2’ on the redox state of electron carriers, led to acceptance
of the ‘Z’-scheme proposed in 1960 by Robert
(Robin) Hill and Fay Bendall. By 1963, the concept
of the requirement of the two light reactions and two pigment systems for the production of the reducing
power (NADPH) in oxygenic photosynthesis became
an established fact. This was evident when ‘photosynthetikers’
met at the Airlie House in Warrenton,
Virginia, for a conference on ‘Photosynthetic Mechanisms
of Green Plants.’ Jack Myers, in this issue,
discusses his views on the history of this milestone
in photosynthesis research. Clearly, the controversy
between Otto Warburg and Robert Emerson on the
minimum quantum requirement of oxygen evolution
was solved in favor of Emerson: a minimum of 8–12
photons per oxygen.