The features of light propagation in plant leaves depend on the long-period ordering in chloroplasts and the spectral characteristics of pigments. This work demonstrates a method of determining the hidden ordered structure. Transmission spectra have been determined using transfer matrix method. A band gap was found in the visible spectral range. The effective refractive index and dispersion in the absorption spectrum area of chlorophyll were taken into account to show that the density of photon states increases, while the spectrum shifts towards the wavelength range of effective photosynthesis.

Calculations were performed using the transfer matrix of one-dimensional photonic crystals with low contrast and asymmetric structures of different periods. Such structures have been found in many plants. When joining two successively connected sublattices with different periods, an increase is observed in the amplitude of the electromagnetic field and the density of photon states inside the structure, and their change depends on the asymmetry of the thickness of the sublattices

It is shown that features of light propagation in plant leaves depend on the long-range ordering in chloroplasts and spectral characteristics of pigments.

Subject of study. The rate of electron transfer between plant photosystems based on fluorescence measurements and calculated density graphs of photon processes is studied. Aim of study. The purpose of this paper is to determine how the structural and optical parameters of plants are affected by their growth conditions. Method. The morphology of chloroplasts was examined by electron microscopy of tissue samples of barley flag leaves grown under the same intensity of illumination in a growing chamber and in the field. The samples underwent full preparation for electron microscopy, including staining with heavy metals to increase the contrast, and were analyzed using a Hitachi HT 7700 transmission electron microscope. Chlorophyll fluorescence parameters of the flag leaves were measured in vivo using the LI-6800 photosynthesis system in a closed leaf chamber that included a built-in fluorimeter. Main results. The role of structural coloration caused by interference and diffraction of light on structural elements of a green leaf having a period comparable with the wavelength of light has only been described in recent years. The study also identified a significantly denser and better-ordered grana structure in the chloroplasts of barley leaf cells grown under artificial conditions. Despite this difference, the maximum quantum yield of Photosystem II in both samples lay in the range of values typical for plants in their normal physiological state. Since electron transport is highly dependent on the spatial organization of the photosynthetic apparatus in the chloroplast thylakoid membranes, the denser “packing” of grana will clearly support more efficient electron transport because the molecular complexes involved in the process are closely arranged. We found that the electron transport rate was different for the plants grown in the field and those grown in the chamber. The electron transport rate for the plants grown in the growth chamber was 1.7 times faster than that for plants grown in the field. Thus, numerical calculations and the spectroscopy/electron microscopy results showed a connection between the photon state density, electron transport rate, and the occurrence of chemical reactions during photosynthesis. Practical significance. Comparing the photosynthetic parameters of the same plants grown in different environments provides useful information on the mechanism behind the photosynthesis process. Identification of the main factors (quantity and quality of water, external environment, amount of nutrients, etc.) affecting the structure and optical properties of plants will increase agricultural yields and reduce costs by optimizing resources and technological processes.

The study aims to analyze the influence of structural changes in thylakoid membranes, induced by foliar fertilization, on energy transfer in the photosynthetic system using fluorescence spectroscopy methods. Control and experimental plant groups were established for the research. Structural analysis was performed using transmission electron microscopy (TEM), which provided images of ultra-thin leaf sections followed by quantitative assessment of the morphometric parameters of chloroplast grana. Micrograph processing and statistical analysis were carried out using artificial intelligence-based software (GRANA). The functional state of the photosystems was evaluated based on chlorophyll fluorescence spectra were obtained using a spectrofluorometer in a 90-degree geometry mode upon excitation with light at a wavelength of 425 nm. Results. It was found that the application of foliar fertilization leads to a statistically significant structural reorganization of the thylakoid membranes. The experimental samples showed a reduction in the median grana area by ~ 38 % and their perimeter by ~ 16 %, indicating denser and more ordered packing. Simultaneously, fluorescence spectroscopy revealed a narrowing of the peak half-width corresponding to photosystem II by 1.8 nm (8%) in the treated plants. This change indicates a reduction in the energetic heterogeneity of the antenna complexes and an increase in the efficiency of excitation energy transfer. Conclusion. Based on the comprehensive studies, it was concluded that the primary mechanism of action of foliar fertilizers is the optimization of the thylakoid membrane nanostructure, which, within the concept of photonic crystals, creates more favorable conditions for light energy conversion. An increase in the regularity of the ultrastructural organization was demonstrated. The obtained results confirm the potential of using fluorescence spectroscopy as a rapid, non-invasive method for diagnosing the physiological state of plants in closed space systems.

The magnetization and anisotropy of magnetic susceptibility of a 5CB nematic liquid crystal doped three extracts containing chlorophylls a and b and carotenoids in different weight percentage has been studied. The extracts have been dissolved in the liquid crystal matrix at a concentration of 2%. The magnetic susceptibility of the substances has been measured by the Faraday-Curie balance method. The field σ(H) and temperature Δχ(T) dependences of molar magnetizations σ and anisotropy of magnetic susceptibility Δχ for the investigated objects have been obtained. The divergence of the σ(H) dependences for the extracts dissolved in the liquid crystal matrix and in acetone has been found. The growth of the Δχ values in the Δχ(T) dependence with an increase in the weight percentage of chlorophylls in the extracts has been established. The influence of molecules of the dopants on the anisotropy of magnetic susceptibility has been evaluated with allowance for the π-electron currents in the conjugated systems of the benzene rings and in the porphyrin nuclei of chlorophylls, as well as in chemical bonds of the aliphatic fragments.