The Study of Basic Photochemical and Photophysical Properties of Membrane-Bound Flavins: The Indispensible Prerequisite for the Elucidation of Primary Physiological Blue Light Action

Review - Flavins as photoreceptors of blue light and their spectroscopic properties

This review describes 1) the development of studies on flavin photoreceptors as blue light photoreceptors in many living organisms: their kinds and functions; 2) the studies on spectroscopic properties of flavins, both their dimers and monomers; 3) nonradiative excitation energy transport in the presence of monomers and fluorescent/nonflurescent FMN dimers (excitation traps). The existence equilibrated luminescent FMN centers, energy migration and excitation sink to FMN dimers are taken into account.

Action dichroism in perception of vectorial photo-excitation in the solar-tracking leaf ofLavatera cretica L

The leaf lamina ofLavatera cretica L. exhibits a diaphototropic response that discriminates between two opposite, constant vectorial excitations by white light beams whose fluence rates differ by as little as 10% (50 versus 45 μmol·m(-2)·S(-1)). The relationship between the response (angular velocity of laminar reorientation) and the fluence-rate ratio is linear. The lamina similarly discriminates between two such excitations by polarized light, one with the electrical vector transverse to the plane of the two beams (θ) and the opposite one with the vector parallel to that plane ([Symbol: see text]). When two such beams were of equal fluence rate, the lamina reoriented towards the [Symbol: see text] beam. When the fluence rate of the θ beam was maintained at 50 μmol·m(-2)·s(-1) and that of the [Symbol: see text] beam was reduced, the response to the latter (angular velocity of laminar reorientation) was reduced progressively. Further reduction in the fluence rate of the [Symbol: see text] polarized beam eventually resulted in reorientation in the opposite direction (towards the θ beam) and the response to the latter increased progressively with the reduction in fluence rate. The equilibrium was at a [Symbol: see text]/θ ratio of 0.62. Measurements of reflectance of oblique beams of [Symbol: see text] and θ polarized light from the upper laminar surface, and of transmittance of such light ghrough the lamina, eliminated the possibility that optical dichroism of the lamina contributed significantly to these results. The implications of this action dichroism to the postulated mechanism of perception of vectorial excitation by these leaves is discussed.