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The ultrastructure of the leaf epidermis and the localization and content of silicon in epidermal cells of the psammophyte Alyssum desertorum Stapf (Brassicaceae) were investigated using electron microscopy and laser confocal microscopy. The study aimed to examine the effect of flooding on the epidermal structure of the leaves, study the presence, localization, and content of silicon in the epidermal cells and determine whether changes in soil moisture affect the silicon content in the leaf epidermis. Silicon inclusions were observed in trichomes and typical epidermal cells on both leaf surfaces, with varying content depending on the cell type, leaf surface, and conditions growth. Soil flooding was found to influence the leaf epidermis ultrastructure and the silicon content in the epidermal cells of A. desertorum. Trichomes and pavement cells were identified as the main accumulators of silicon inclusions and wax-like structures. These findings suggest that changes in leaf microstructure and silicon content contribute to the normal functioning of psammophyte plants and can be considered signs of plant phenotypic plasticity and adaptive markers depending on water supply conditions., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

Comparative analysis of the cellular ultrastructure and pigment content of both submerged and above-water Sagittaria sagittifolia leaves with transmission electron microscopic and biochemical methods were realized. Essential distinctions of S. sagittifolia ultrastructure of photosynthesizing cells in submerged leaves were revealed during the comparison with those in mesophyll cells of above-water leaves. The changes of chloroplast ultrastructure in submerged leaves are examined as the adaptative signs of photosynthesizing cells under influence of altered environment.

The distribution of cellulose in the cells of epidermis and mesophyll of Sium latifolium leaves at the phases of flowering and seedling by the laser-confocal microscopic method has been investigated. The dependence of the relative content of cellulose in cell walls on the tissue type, phase of plant ontogenesis and the environment conditions has been established by using of PASCAL Program. It has been revealed that moderate water deficit leads to decrease of amorphous cellulose content and to increase of crystalline cellulose content during plant growth.

The study of the influence of weak, alternating magnetic field, which was adjusted to the cyclotron frequency of Ca2+ and K+ ions, on the fusion of tobacco and soya protoplasts was carried out using the extra apparatus with ferromagnetic shield. An increase in the frequency of protoplasts fusion in 2-3 times and participation of calcium ions in the induction of protoplast fusion in weak alternating magnetic field have been established.

The goal of our work was a role of phosphorylase (EC. 2.4.1.1) in starch accumulation in plastids of storage parenchyma cells in potato minitubers forming under clinorotation. An increased enzyme activity under the influence of simulated microgravity has been revealed by using the biochemical and electron cytochemical methods. The obtained results suggest the correlation between an increase in phosphorylase activity and acceleration growth rate and senescence of plant storage organs in microgravity.

The major purpose of these experiments were to investigate growth of potato storage organs and starch synthesis in minitubers at slow horizontal clinorotation (2 rpm), which partly mimics microgravity, and a secondary goal was to study the activity and localization of phosphorylase (EC 2.4.1.1) in storage parenchyma under these conditions. Miniplants of Solanum tuberosum L. (cv Adreta) were grown in culture for 30 days for both the vertical control and the horizontal clinorotation. During long-term clinorotation, an acceleration of minituber formation, and an increase of amyloplast number and size in storage parenchyma cells, as well as increased starch content, was observed in the minitubers. The differences among cytochemical reaction intensity, activity of phosphorylase, and carbohydrate content in storage parenchyma cells of minitubers grown in a horizontal clinostat were established by electron-cytochemical and biochemical methods. It is shown that high phosphorylase activity is correlated with increased starch content during extended clinorotation. The results demonstrate the increase in carbohydrate metabolism and possible accelerated growth of storage organs under the influence of microgravity, as mimicked by clinorotation; therefore, clinorotation can be used as a basis for future studies on mechanisms of starch synthesis under microgravity., (c2003 COSPAR. Published by Elsevier Ltd. All rights reserved.)

The effect of long-term clinorotation on potato minituber formation and the structural-functional organization of storage parenchyma cell in minitubers has been studied by using methods of organ culture in vitro, light- and electron microscopy, biochemistry as well as phenological observation. It was established some acceleration of growth, changes in the parenchyma cell ultrastructure and in the starch content as well as an intensification of phosphorylase activity in the storage tissue of minitubers under the influence of simulated microgravity.

It is established that high plant growth and development in microgravity occurred normal. However, the change of plant growth rate is accompanied by the change of carbohydrate metabolism in photosynthesized cells (Kordyum, 1997). The decrease of starch grain size in chloroplasts and the decrease of content cellulose in cell wall were revealed (Sytnik et al., 1984; Nedukha, 1996). The change carbohydrate metabolism in photosynthesized organs could influence on the growth of underground organs and content of storage carbohydrates in these organs. Therefore, the aim of our study was to investigate the long-term clinorotation influence on the formation, structure of potato minitubers and content of starch and sugars in minitubers.

Formation and structure of potato minitubers grown aseptically for 30 days on a horizontal clinostat and in stationary control have been studied by light and electron microscopy. It was demonstrated that the number of plants that formed minitubers, their size and fresh weight, was higher when clino-rotated than in the stationary control. It was revealed that the amount of amyloplasts in parenchyma cell sections was doubled in minitubers formed under clino-rotation. Other factors (shape of minitubers and size of reserve parenchyma cells) did not differ from the stationary control. The changes in amyloplast ultrastructure suggest accelerated cell maturity of potato reserve parenchyma in extended clino-rotation., (c 2001 COSPAR. Published by Elsevier Science Ltd. All rights reserved.)

Plants are an important component of the controlled ecological life-support system (CELSS) for future long-term spaceflight and the International Space Station. Therefore, it is critical to understand the susceptibility of plants to pathogen infection in microgravity. An increase in both hyphal growth and sporangia formation in Phycomyces blakes in microgravity has been described. Plant cell walls, a critical barrier for pathogen invasion, have been reported to undergo changes in microgravity including changes in the wall structure. For example, a decrease in the crystalline cellulose content and an increase in the hemicellulose content in cell walls of plants grown in clinostats and in microgravity have been reported. Based of these previous reports, we hypothesize that susceptibility of plants to pathogen infection in microgravity would be increased relative to the ground control.

The study of pathogenicity of higher plants under conditions of microgravity is of great importance for the future production of food in space. Previous work suggests that microgravity affects both microbes and plants. Bacterial numbers increased after 17 days in an algae-bacterium association on the biosatellite "Kosmos-1887". This was speculated to result from an increase in the multiplication rate of the bacteria. Sporangia of both Actinomices brevis, in the shuttles "Soyuz-19" and "Appolon", and Phycomyces blakes, in biosatellite "Kosmos-936", formed after 10 days in microgravity. Sporangia did not form in the ground controls in the same time suggesting that the rate of fungal development is enhanced in microgravity. Plant responses to pathogens in microgravity have not been studied, however, microgravity profoundly impacts plant cell development, cytology, and physiology. In microgravity, developing cell walls are thinner and contain less lignin than ground-grown plants. The demonstrated effects of microgravity on both plants and microbes lead us to hypothesize that plants may be more susceptible to pathogens under conditions of microgravity. The aim of this study was to determine the influence of microgravity on the susceptibility of soybean to the fungal root rot pathogen, Phytophthora sojae.

It was established early that the signs of accelerated aging of both plant leaves and of moss chloronema were observed in seedlings of high plants and in Funaria hygrometrica protonema under long term growing under weightlessness. It was observed the structure changing of photosynthesizing cells in Arabidopsis thaliana, Epidendrum radicans and Pisum sativum leaves. Authors found out the extension and vesiculation of thylakoids between chloroplast granas. They observed thylakoids partly destroying under 96 and 110 days microgravity influence. But some questions are still opened: 1. Are these changes consequence of accelerated differentiation and aging photosynthesizing cells? 2. Do the definite changes appear in photosynthesizing cells during short-term microgravity influence? Therefore the study of mesophyll cells ultrastructure of leaves that finished growth by tension in microgravity was the idea of our experiment.