  Circular polarization spectroscopy has proven to be an indispensable tool in
photosynthesis research and (bio)-molecular research in general. Oxygenic
photosystems typically display an asymmetric Cotton effect around the
chlorophyll absorbance maximum with a signal $\leq 1 \%$. In vegetation, these
signals are the direct result of the chirality of the supramolecular
aggregates. The circular polarization is thus directly influenced by the
composition and architecture of the photosynthetic macrodomains, and is thereby
linked to photosynthetic functioning. Although ordinarily measured only on a
molecular level, we have developed a new spectropolarimetric instrument,
TreePol, that allows for both laboratory and in-the-field measurements. Through
spectral multiplexing, TreePol is capable of fast measurements with a
sensitivity of $\sim 1*10^{-4}$ and is therefore suitable of non-destructively
probing the molecular architecture of whole plant leaves. We have measured the
chiroptical evolution of \textit{Hedera helix} leaves for a period of 22 days.
Spectrally resolved circular polarization measurements (450-900 nm) on whole
leaves in transmission exhibit a strong decrease in the polarization signal
over time after plucking, which we accredit to the deterioration of chiral
macro-aggregates. Chlorophyll \textit{a} levels measured over the same period
by means of UV-Vis absorption and fluorescence spectroscopy showed a much
smaller decrease. With these results we are able to distinguish healthy from
deteriorating leaves. Hereby we indicate the potency of circular polarization
spectroscopy on whole and intact leaves as a nondestructive tool for structural
and plant stress assessment. Additionally, we underline the establishment of
circular polarization signals as remotely accessible means of detecting the
presence of extraterrestrial life.
