Optical processes in photosynthesis

Abstract

A review of the state and analysis of works related to optical processes of photosynthesis are given. Particular attention is paid to the work on the investigation of these processes in iridoplasts and chloroplasts with photonic crystal structure. From a general point of view, a photonic crystal (PhC) is a superlattice with a characteristic scale of periodicity of permittivity (refractive indices) of the order of the wavelength of the light wave. In such structures, the forbidden bands occur in the spectrum of electromagnetic waves. This means that in a given spectral range the light of any polarization cannot enter the PhC or exit in any direction. An important property of PhC is high degree of localization of electromagnetic waves on the lattice defects. In this case, defective energy levels manifest themselves in the forbidden zones of the PhC. An atom or molecule emit a quantum with a frequency corresponding to a defective mode. Most of the works dealing with the study of optical processes of photosynthesis have not taken into account the features of light propagation in structures. Periodic structures have been found in the plant and animal world. This paper presents the effect of a long-period structure on the optical properties and local characteristics of light waves, including the transmission and reflection spectrum, as well as the distribution of the electromagnetic field in the layered structure. Based on modern mathematical apparatus, the main spectral and optical characteristics were calculated using the example of a begonia plant. In recent works describing the propagation of light, the long-period structure was not taken into account. However, for the interpretation of the results, concepts (antenna, reaction center, the presence of two photosystems) without a detailed description of the physical nature were introduced. In addition, we had to employ a resonance mechanism for the transfer of excitation energy from the donor molecule to the acceptor molecule and quantum coherence. The analysis of the data obtained within the framework of a unified approach made it possible to explain the mechanism of the effect on photosynthesis, namely, the appearance of two photosystems (division of the stop zone into two parts), the feature of the long-wavelength quantum yield, its amplification (Emerson effect), including the red boundary shift, the efficiency of photosynthesis with additional irradiation and the expansion of the absorption region.

Keywords

• optics
• photonic crystals
• photosynthesis