ORIENTATION OF SHORT WAVELENGTH AND LONG WAVELENGTH PROTOCHLOROPHYLL SPECIES IN GREENING CHLOROPLASTS

Abstract

Abstract— The orientation of protochlorophyll and Chi species with respect to the plane of thylakoid membranes was studied by measuring the fluorescence polarization ratio in magnetically oriented chloroplasts isolated from greening maize leaves and cucumber cotyledons. With viewing direction parallel to the plane of the photosynthetic membranes, in the spectral region of 620–660 nm, fluorescence polarization ratios of 1.0 were observed, whereas at longer wavelengths the fluorescence polarization ratios were much higher, and similar to that of fully green chloroplasts. The same result was obtained with chloroplasts isolated from leaves fed by δ‐amino levulinic acid. These data indicate that the emitting oscillators of the short and long wavelength protochlorophyll species are oriented at random with respect to the plane of thylakoid membranes. Isotropy of the protochlorophyll species is discussed in terms of isotropic structures containing Chi precursors.