[Ultrastructure and pigment composition of Sagittaria sagittifolia L. leaves].

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.

[Cytochemical and biochemical study of cellulose content and localization in Slum latifolium leaves under condition of water deficit].

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 effects of extended clinorotation on potato minituber formation and structure.

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.

High phosphorylase activity is correlated with increased potato minituber formation and starch content during extended clinorotation.

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.

Plants, plant pathogens, and microgravity--a deadly trio.

Plants grown in spaceflight conditions are more susceptible to colonization by plant pathogens. The underlying causes for this enhanced susceptibility are not known. Possibly the formation of structural barriers and the activation of plant defense response components are impaired in spaceflight conditions. Either condition would result from altered gene expression of the plant. Because of the tools available, past studies focused on a few physiological responses or biochemical pathways. With recent advances in genomics research, new tools, including microarray technologies, are available to examine the global impact of growth in the spacecraft on the plant's gene expression profile. In ground-based studies, we have developed cDNA subtraction libraries of rice that are enriched for genes induced during pathogen infection and the defense response. Arrays of these genes are being used to dissect plant defense response pathways in a model system involving wild-type rice plants and lesion mimic mutants. The lesion mimic mutants are ideal experimental tools because they erratically develop defense response-like lesions in the absence of pathogens. The gene expression profiles from these ground-based studies will provide the molecular basis for understanding the biochemical and physiological impacts of spaceflight on plant growth, development and disease defense responses. This, in turn, will allow the development of strategies to manage plant disease for life in the space environment.

The influence of combined magnetic field on the fusion of plant protoplasts.

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.

Effects of weightlessness on photosynthesizing cells structure of plant.

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.

Clinorotation [correction of Clinoratation] effects on the structural-functional response in potato minitubers.

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.

The interaction of microgravity and ethylene on the ultrastructure cell and Ca2+ localization in soybean hook hypocotyl.

Calcium ions are secondary messenger in numerous cellular processes of plant grown at 1 g. Ca2+ are connected with oxygen atoms, of pectin carboxy groups and/or with H(+)-groups of protein (Roux and Slocum, 1982; Hepler and Wayne, 1985). The influence of altered gravity on the calcium balance in some cells is established. The increased synthesis of ethylene in plant grown in microgravity caused the change of the structural-functional organization of cell (Hensel and Iversen, 1980; Hilaire et al., 1996). Available data put the new question: how do high ethylene level and microgravity influence on the redistribution of Ca2+ in cell of seedling in early stage of growth? Therefore, the goal of our data was the comparable study of the cell ulltrastructure and localization of Ca2+ in hook hypocotyl of soybean seedling under interaction of microgravity and ethylene.

Effect of simulated microgravity on potato minituber formation and structure.

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.

Electron-cytochemical study of Ca2+ in cotyledon cells of soybean seedlings grown in microgravity.

Microgravity and horizontal clinorotation are known to cause the rearrangement of the structural-functional organization of plant cells, leading to accelerated aging. Altered gravity conditions resulted in an increase in the droplets volume in cells and the destruction of chloroplast structure in Arabidopsis thaliana plants, an enhancement of cytosolic autophagaous processes, an increase in the respiration rate and a greater number of multimolecular forms of succinate- and malate dehydrogenases in cells of the Funaria hygrometrica protonema and Chlorella vulgaris, and changes in calcium balance of cells. Because ethylene is known to be involved in cell aging and microgravity appears to speed the process, and because soybean seedlings grown in space produce higher ethylene levels we asked: 1) does an acceleration of soybean cotyledon cell development and aging occur in microgravity? 2) what roles do Ca2+ ions and the enhanced ethylene level play in these events? Therefore, the goal of our investigation was to examine of the interaction of microgravity and ethylene on the localization of Ca2+ in cotyledon mesophyll of soybean seedlings.

Growth in microgravity increases susceptibility of soybean to a fungal pathogen.

The influence of microgravity on the susceptibility of soybean roots to Phytophthora sojae was studied during the Space Shuttle Mission STS-87. Seedlings of soybean cultivar Williams 82 grown in spaceflight or at unit gravity were untreated or inoculated with the soybean root rot pathogen P. sojae. At 3, 6 and 7 d after launch while still in microgravity, seedlings were photographed and then fixed for subsequent microscopic analysis. Post-landing analysis of the seedlings revealed that at harvest day 7 the length of untreated roots did not differ between flight and ground samples. However, the flight-grown roots infected with P. sojae showed more disease symptoms (percentage of brown and macerated areas) and the root tissues were more extensively colonized relative to the ground controls exposed to the fungus. Ethylene levels were higher in spaceflight when compared to ground samples. These data suggest that soybean seedlings grown in microgravity are more susceptible to colonization by a fungal pathogen relative to ground controls.

Effects of microgravity on the susceptibility of soybean to Phytophthora sojae.

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.

Root meristem ultrastructure of soybean seedlings infected with a pathogenic fungus in microgravity.

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.