Abstract
Microscopic linear dichroism of fluorescence spectra manifested by polarization dependence in excitation was studied on chlorolplasts in Zea mays leaves. There are at least two spectral components in the room temperature microscopic spectra induced by two-photon excitation with near infrared pulsed laser. One is attributable to photosystem II and its associated antenna, the other is photosystem I and antenna. The former component is highly localized in several regions with a submicrometer dimension, the latter is almost homogeneously distributed over the whole chloroplasts. The two components are also clearly distinguished by excitation polarization dependence. It has been also found that appearance of small abnormal regions with a third spectral feature that has been unreported, which probably indicates a transient state of thylakoid membrane. Combination of fluorescence spectromicroscopy with linear dichroism measurements will thus help us improve modeling of thylakoid membrane structure and changes based on optical microscopy of live chloroplasts.
