  Photosynthetic eukaryotes show a remarkable variability in photosynthesis,
including large differences in light harvesting proteins and pigment
composition. In vivo circular spectropolarimetry enables us to probe the
molecular architecture of photosynthesis in a non-invasive and non-destructive
way and, as such, can offer a wealth of physiological and structural
information. In the present study we have measured the circular polarizance of
several multicellular green, red and brown algae and higher plants, which show
large variations in circular spectropolarimetric signals with differences in
both spectral shape and magnitude. Many of the algae display spectral
characteristics not previously reported, indicating a larger variation in
molecular organization than previously assumed. As the strengths of these
signals vary by three orders of magnitude, these results also have important
implications in terms of detectability for the use of circular polarization as
a signature of life.
