Effect of external factors on the optical and structural characteristics of higher plants

https://doi.org/10.1364/JOT.92.000138

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.