Andreas Blennow, Department of Plant and Environmental Sciences, University of Copenhagen, Denmark
Virginijus Barzda, Department of Chemical and Physical Sciences, Department of Physics and Institute for Optical Sciences, University of Toronto, Canada
Second harmonic generation (SHG) microscopy is employed to
study changes in crystalline organization due to altered gene expression and
hydration in barley starch granules. SHG intensity and susceptibility ratio
values (R’SHG) are obtained using reduced Stokes-Mueller polarimetric
microscopy. The maximum R’SHG values occur at moderate moisture
indicating the narrowest orientation distribution of nonlinear dipoles from
the cylindrical axis of glucan helices. The maximum SHG intensity occurs
at the highest moisture and amylopectin content. These results support the
hypothesis that SHG is caused by ordered hydrogen and hydroxyl bond
networks which increase with hydration of starch granules.