It is now clear that cyclic electron flow, long debated and often
doubted is real and important in higher plants. The coming years will
no doubt throw up new and much more detailed evidence as to how
this pathway functions and which polypeptides and co-factors are
required. It will also no doubt lead to extensive continued debate as to
the relative importance of different proteins and probably even as to
whether certain pathways exist at all. It should be remembered, when
taking part in such debates, that nature is not simple and clean and
does not always come up with the same answer. Just because tobacco
contains only trace amounts of the NDH complex, for example, this
can not be extrapolated to different species of the same genus, let
alone to different genera or families. Plant physiologists, especially
ecophysiologists, have long recognised that the differences between
species are far more important than looking for a single answer to a
simple question. A particular pathway may be dominant in one
species but largely or totally absent in another and understanding this
in the context of the ecology of the plants concerned will give us
powerful insights into the roles of limitations of different pathways.
Recent advances in high throughput sequencing and quantitative
proteomics will mean that we will be able to gain detailed molecular
insights into a much broader range of species in the future, however a
true understanding of cyclic electron flow, or of any other physiological
process, will only be possible if research is lead by an appreciation
of the physiology and ecology of the plants concerned.