Light intensity distribution in thylakoids and the polarity of
the photovoltage effect

Geza Meszena, Hans V. Westerhoff

Biopysical Chemistry 48: 321-336 (1994)

Summary

     The spatial organization in photosystem containing
chloroplast membranes is such that some of the relevant distances
are of the order of the wavelength of the absorbed light.
Consequently, interference between incident and reflected light
may occur. This paper calculates the heterogeneity to be expected
in the resultant light intensity. The pattern is determined by
the wavelength-dependent phase shift of light during scattering.
We show that in stroma membranes this heterogeneity may well be
responsible for paradoxical polarities of the photovoltaic effect
in which flash illumination of a chloroplast suspension generates
a macroscopic electric potential opposite to that expected from
shading. The grana stack dimensions are calculated to lead to the
classical picture of shading, consistent with a 'normal'
photovoltaic effect. We demonstrate that the simultaneous
presence of stroma and grana membranes may explain the observed
wavelength dependence of the polarity of the photovoltaic effect.