Weitere untersuchungen über die Orientierung der Photosynthese-Pigmente im Algen-Chloroplasten

Abstract

Summary In chloroplasts of Mesotaenlum caldariorum var. caldariorum and of Mougeotia spec, both in edge and face position, an absorption dichroism has been measured using monochromatic light of λ = 435 to 475 and 620 to 680 nm: polarized light vibrating in a plane parallel to the long axis of the chloroplasts is more strongly absorbed than light vibrating at right angles to it. This has been measured, though with quantitative differences, for the blue as well as for the red region of light, in contrast to the fact that the electron oscillators in the chlorophyll molecule, responsible for the absorption of blue and red light respectively, are orientated at right angles to each other. It may be concluded, therefore, that the chlorophyll molecule orientates itself differently according to the light quality: in red light, the chlorophyll molecules become orientated in a preferential direction whereas in blue light they do not. A further complication arises from the conclusion (as a result from comparing with physiological response) that in the thylakoid membranes two populations of chlorophyll molecules are present with different dichroic orientations. Finally, if the chloroplast is observed in the edge position, the measurable dichroism is quantitatively different in the peripheral lamellary system from that in the inner system. The fraction of chlorophyll orientated parallel to the chloroplast axis amounts to 16 and 7 percent in the peripheral and the inner system, respectively, in Mesotaenium , and to 18 and 9 percent, respectively, in Mougeotia .