Comparison Study of Gravity-Dependent Displacement of Amyloplasts in Statocytes of Cress Roots and Hypocotyls

In this study, the kinetics of gravity-dependent movement of amyloplasts (statoliths) along root statocytes and hypocotyls (endodermis cells) has been analyzed and compared in order to testify cytoskeleton involvement in the displacement of statoliths in cress (Lepidium sativum L.) seedling statocytes. After 32 h of growth at 1 g or under a fast clinorotation (50 rpm), the seedlings were treated for 24 min as follows: exposition to clinorotation or 180° inversion and the action of gravitational force in root tip or hypocotyl tip direction. Statolith displacement was studied by light microscopy on semi-thin longitudinal sections of hypocotyls and root caps, measuring the distance between the centre of plastids and morphological cell bottom. Considerable temporal differences have been determined between the kinetics of the longitudinal motion of amyloplasts in root and hypocotyl statocytes of 1-g seedlings upon exposition to fast clinorotation and inversion. In statocytes of both organs of seedlings grown under fast clinorotation, the gravity provoked displacement of statoliths in the direction of its action; however, the displacement was much faster in hypocotyl than in root statocytes. It has been assumed that the gravity-determined longitudinal transport of amyloplasts, both in hypocotyl endodermic cells and root statocytes of cress seedlings, is modulated by the cytoskeleton.     

Clinorotation Affects the Ultrastructure of Pea Root Mitochondria

Effects of clinorotation on the mitochondrial ultrastructure in cells of meristem, distal and central elongation zones of 3- and 5-day-old etiolated roots of pea seedling roots were studied. It was shown that mitochondria in cells of examined root growth zones revealed a different sensitivity to clinorotation. The ultrastructure of mitochondria in the meristem and central elongation zone cells did not substantially change in comparison with stationary control. At the same time, changes in the mitochondrial ultrastructure in cells of the distal elongation zone under clinorotation were observed, namely: decrease in the size of mitochondria, as well as increase in both matrix electron density and crista volume. Such changes in the mitochondrial ultrastructure under clinorotation are supposed to display the rearrangements of energy metabolism in cells of the distal elongation zone in these conditions.     

The stress protein level under clinorotation in context of the seedling developmental program and the stress response

Heat-shock proteins (HSP70 and HSP90) are present in plant cells under the normal growth conditions. At the same time, a variety of environmental disruptions results in their rapid synthesis as a substantial part of adaptation. HSP amounts can be indicative of a cellular stress level. Altered gravity (clinorotation) is unnatural for plants, so it may be a kind of stress. The aim of this study was to analyze the influence of horizontal clinorotation on the HSP70 and HSP90 level during seedling development. Pea (Pisum sativum L.) seedlings grown for 3 days from seed imbibitions in stationary control and under slow clinorotation (2 rpm) are used for this investigation. Western blot analysis indicated that HSP70 and HSP90 were abundant in the embryos of dry seeds and their amount decreased significantly during seed germination. But under horizontal clinorotation, their level in seedlings remained higher compared to the control. Furthermore, a comparison of the influence of horizontal and vertical clinorotation on the HSP level was carried out. On the ELISA data, HSP70 and HSP90 amounts in the 3-day old seedlings were higher after horizontal clinorotation than after vertical. The obtained data show an increased HSP70 and HSP90 level in pea seedlings under clinorotation. Both, rotation and change in the cell position relatively to a gravity vector affect the HSP level.     

Distribution of Calcium Ions in Cells of the Root Distal Elongation Zone Under Clinorotation

Currently, calcium ions are known to play a crucial role in the vital activity of plant cells and in stimulus–response coupling for many environmental signals, altered gravity included. The available data on changes in Ca^2?+? distribution and concentration in the cells of different organisms influenced by altered gravity allow to suggest that microgravity affects the calcium messenger system, and provide new insight for the understanding of calcium-and gravity-dependent cellular processes. We have studied with confocal microscopy the distribution and relative content of calcium ions in the Beta vulgaris root distal elongation zone cells grown under slow horizontal clinorotation, reproducing one of the microgravity particularities, namely the absence of an orienting action of the gravity vector, compared to control conditions. We demonstrate that Ca^2?+? relative content is 1.3 times higher in the roots of seedlings grown upwards and 1.2 times higher in the seedlings grown downwards compared to the control. Based on obtained data, taking into account the specific physiological properties of cells in the distal elongation zone, it is supposed that, under clinorotation, enhanced Ca^2?+? relative content affects Ca^2?+?-dependent cytoskeleton reorganization involved in cell gravisensing in altered gravity.     

Chlorophyll,Carotenoid and Anthocyanin Accumulation in Mung Bean Seedling Under Clinorotation

The accumulation of plant pigments in mung bean (Vigna radiata L.) seedlings was measured after clinorotation (2 rpm for 2-4 days), and compared to a stationary control. The pigments measured included chlorophyll and carotenoid in primary leaves, and the anthocyanin in seedlings. While significant changes in chlorophyll and carotenoid accumulation were not observed during the initial 2 to 4 days of cultivation, by day 4 the seedlings grown on the clinostat had lower levels of anthocyanin, compared to those in the control seedlings. To further detail the cause for the observed reduction in anthocyanin accumulation under altered gravity conditions, seedlings were grown in the presence of silver nitrate, a known ethylene inhibitor, for 4 days, since it is known ethylene has a negative impact on anthocyanin accumulation. Silver nitrate promoted anthocyanin accumulation in the clinostat seedlings, and as a result there was no significant difference between the control and clinostat seedlings in anthocyanin accumulation. The results suggest that slow clinorotation negatively impacts anthocyanin pigmentation in mung bean seedlings, with endogenous ethylene suspected to be involved in this.     

ARADISH - Development of a Standardized Plant Growth Chamber for Experiments in Gravitational Biology Using Ground Based Facilities

Plant development strongly relies on environmental conditions. Growth of plants in Biological Life Support Systems (BLSS), which are a necessity to allow human survival during long-term space exploration missions, poses a particular problem for plant growth, as in addition to the traditional environmental factors, microgravity (or reduced gravity such as on Moon or Mars) and limited gas exchange hamper plant growth. Studying the effects of reduced gravity on plants requires real or simulated microgravity experiments under highly standardized conditions, in order to avoid the influence of other environmental factors. Analysis of a large number of biological replicates, which is necessary for the detection of subtle phenotypical differences, can so far only be achieved in Ground Based Facilities (GBF). Besides different experimental conditions, the usage of a variety of different plant growth chambers was a major factor that led to a lack of reproducibility and comparability in previous studies. We have developed a flexible and customizable plant growth chamber, called ARAbidopsis DISH (ARADISH), which allows plant growth from seed to seedling, being realized in a hydroponic system or on Agar. By developing a special holder, the ARADISH can be used for experiments with Arabidopsis thaliana or a plant with a similar habitus on common GBF hardware, including 2D clinostats and Random Positioning Machines (RPM). The ARADISH growth chamber has a controlled illumination system of red and blue light emitting diodes (LED), which allows the user to apply defined light conditions. As a proof of concept we tested a prototype in a proteomic experiment in which plants were exposed to simulated microgravity or a 90° stimulus. We optimized the design and performed viability tests after several days of growth in the hardware that underline the utility of ARADISH in microgravity research.     

Physiological Responses of Synechocystis sp. PCC 6803 under Clinorotation

Photosystem efficiency and the characteristic on oxidative stress were examined to elucidate the metabolic responses of Synechocystis sp. PCC 6803 to short-term clinorotation. Results compiled when using clinostat to simulate microgravity for 60?h, showed that clinorotation clearly prohibited the photochemical quantum yield, but promoted the synthesis of chlorophyll and total protein. This may be a compensatory mechanism for the algal cell to maintain its normal metabolism. An increased malondialdehyde (MDA) content of algal cell upon clinorotation, together with an enhanced catalase (CAT) activity was observed during the whole period of clinorotation. One conclusion is that short-term clinorotation acts as a kind of stress, and that these physiological responses may be a special way for an algal cell to adapt itself to a different environment other than earth gravity.     

Investigation on photogenerated radicals of some carboxylates in solution and in aqueous dispersions of AgBr

Abstract

The photogenerated free radicals from formate, oxalate and acetate in aqueous solutions without and with dispered AgBr grains under illuminations of 355 nm laser light, natural light and monochromatic red, green or blue light were detected by electron spin resonance with spin-trap DMPO. The results showed that: (a) ·CO₂^? radicals were produced in the formate solution by all of these illuminations; (b) the signals of ·CO₂^? radicals were greatly intensified when an AgBr dispersion was present in the formate solution; (c) the signals of ·CO₂^? radicals in the oxalate solution were also detected and intensified when an AgBr dispersion was present, but only after illumination by the 355 nm laser; (d) ·CH₃ radicals, instead of ·CO₂^?, were weakly detected in the acetate solution, but only in the presence of AgBr under illumination by the 355 nm laser. The photochemical behaviour of these carboxylates, particularly formate and oxalate, perhaps implies their capability for trapping photogenerated holes and their potential for acting as a hole converter to an effective electron carrier.     

Cytosolic Calcium Concentration Changes in Neuronal Cells Under Clinorotation and in Parabolic Flight Missions

All life on earth has been established under conditions of stable gravity of 1g. Nevertheless, in numerous experiments the direct gravity dependence of biological processes has been shown on all levels of organization, from single molecules to humans. To study the effects especially of microgravity on biological systems, a variety of platforms are available, from drop towers to the ISS. Due to the costs of these platforms and their limited availability, as an alternative, numerous simulators have been developed for so called “simulated” microgravity. A classical systems is a clinostat, basically rotating a sample around one axis, and by integration of the gravity vector for 360° arguing that thus the effects of gravity are depleted. Indeed, a variety of studies has shown that taking out the direction of gravity from a biological system often results in consequences similar to the exposure of the system to real microgravity. Nevertheless, the opposite has been shown, too, and as a consequence the relevance of clinostats in microgravity research is still under discussion. To get some more insight into this problem we have constructed a small fluorescence clinostat and have studied the effects of clinorotation on the cytosolic calcium concentration of neuroglioma cells. The results have been compared to experiments with identical cells in real microgravity, utilizing parabolic flight missions. Our results show that in case of a cell suspension used in a small florescence clinostat within a tube diameter of 2mm, the effects of clinorotation are comparable to those under real microgravity, both showing a significant increase in intracellular calcium concentration.     

Tubulin Cytoskeleton in Arabidopsis thaliana Root Cells Under Clinorotation

The effect of horizontal clinorotation (2 rpm) on the spatial organization of cortical microtubules (CMTs) in the living Arabidopsis root cells has been investigated. MTs were visualized by using a stably transformed line of transgenic Arabidopsis thaliana expressing GFP-MAP4 fusion protein. To monitor total changes in MT dynamics, the sensitivity to MT-inhibitor 5 μM/l oryzalin was used as an indicator. It was shown that CMTs in the distal elongation zone (DEZ) of clinorotated 5 day old seedlings exhibited a higher degree of disorder and also they were more sensitive to oryzalin. We suggest that rearrangement of CMTs in DEZ cells under clinorotation is caused by fast rate of MT dynamic turnover.     

Use of multiple loads to extract continuous isoclinic fringes by phase shifting technique

Using a monochromatic light source for illumination, a new approach is proposed which uses two different loads to get continuous isoclinic fringes. A new set of optical arrangements in a plane polariscope setup is proposed for this purpose. The intensity equations are obtained by Jones calculus. The methodology is verified for the problem of a disc under diametral compression.     

Changes in Gene Expression of E. coli under Conditions of Modeled Reduced Gravity

Relatively few studies have examined bacterial responses to the reduced gravity conditions that are experienced by bacteria grown in space. In this study, whole genome expression of Escherichia coli K12 under clinorotation (which models some of the conditions found under reduced gravity) was analyzed. We hypothesized that phenotypic differences at cellular and population levels under clinorotation (hereafter referred to as modeled reduced gravity) are directly coupled to changes in gene expression. Further, we hypothesized that these responses may be due to indirect effects of these environmental conditions on nutrient accessibility for bacteria. Overall, 430 genes were identified as significantly different between modeled reduced gravity conditions and controls. Up-regulated genes included those involved in the starvation response (csiD, cspD, ygaF, gabDTP, ygiG, fliY, cysK) and redirecting metabolism under starvation (ddpX, acs, actP, gdhA); responses to multiple stresses, such as acid stress (asr, yhiW), osmotic stress (yehZYW), oxidative stress (katE, btuDE); biofilm formation (lldR, lamB, yneA, fadB, ydeY); curli biosynthesis (csgDEF), and lipid biosynthesis (yfbEFG). Our results support the previously proposed hypothesis that under conditions of modeled reduced gravity, zones of nutrient depletion develop around bacteria eliciting responses similar to entrance into stationary phase which is generally characterized by expression of starvation inducible genes and genes associated with multiple stress responses.     

Electromagnetic-field calculations for irregularly shaped, layered cylindrical particles with focused illumination

Theoretical procedures are presented for the determination of internal and external electromagnetic fields for the plane two-dimensional problem of an arbitrary monochromatic field (e.g., a focused laser light sheet) incident upon an irregularly shaped, layered cylindrical particle. Equations for the arbitrary illumination of a layered circular cylindrical particle are also given as a special case of the general solution.     

Analysis of Statoliths Displacement in <Emphasis Type="Italic">Chara</Emphasis> Rhizoids for Validating the Microgravity-Simulation Quality of Clinorotation Modes

In single-celled rhizoids of the green algae Chara, positively gravitropic growth is governed by statoliths kept in a dynamically stable position 10–25 μ m above the cell tip by a complex interaction of gravity and actomyosin forces. Any deviation of the tube-like cells from the tip-downward orientation causes statoliths to sediment onto the gravisensitive subapical cell flank which initiates a gravitropic curvature response. Microgravity experiments have shown that abolishing the net tip-directed gravity force results in an actomyosin-mediated axial displacement of statoliths away from the cell tip. The present study was performed to critically assess the quality of microgravity simulation provided by different operational modes of a Random Positioning Machine (RPM) running with one axis (2D mode) or two axes (3D mode) and different rotational speeds (2D), speed ranges and directions (3D). The effects of 2D and 3D rotation were compared with data from experiments in real microgravity conditions (MAXUS sounding rocket missions). Rotational speeds in the range of 60–85 rpm in 2D and 3D modes resulted in a similar kinetics of statolith displacement as compared to real microgravity data, while slower clinorotation (2–11 rpm) caused a reduced axial displacement and a more dispersed arrangement of statoliths closer to the cell tip. Increasing the complexity of rotation by adding a second rotation axis in case of 3D clinorotation did not increase the quality of microgravity simulation, however, increased side effects such as the level of vibrations resulting in a more dispersed arrangement of statoliths. In conclusion, fast 2D clinorotation provides the most appropriate microgravity simulation for investigating the graviperception mechanism in Chara rhizoids, whereas slower clinorotation speeds and rotating samples around two axes do not improve the quality of microgravity simulation.     

Multifunctional photochromic spiropyran dendrimers and their relaxation behaviors of photochromism

First and second generation dendrimers that exhibit unique photochromic behavior were synthesized through multi-step reactions. Their photochromic behavior under illumination of monochromatic ultraviolet light (λ = 365 nm) was investigated. The colorless dendritic dye solution and its film exhibit typical ring opening and E/Z geometrical transformation from spiropyran to merocyanine. The stability of photochromism in the two dendrimers was much better than that observed in the dye-attached polymer or dye-doped polymer system. Particularly, blend material system of photochromic dendrimer and photocrosslinkable dendrimer showed much better stability of the photochromism.     

A laboratory objective spectropyrometer

Conclusion The SPP-58 objective spectropyrometer can be used mainly in state inspection laboratories for measurement techniques for checking standard temperature lamps which are calibrated in brightness temperatures.By means of this spectropyrometer, temperature lamps which are calibrated in color temperatures can be checked by measuring monochromatic brightness temperatures corresponding to two different wavelengths.Moreover, this spectropyrometer can be successfully used for accurate measurement of brightness and color temperatures and also for measuring monochromatic brightness, illumination, luminous intensity, and other light quantities.     

Bidirectional scattering distribution functions of maple and cottonwood leaves

We present our investigations into the optical scattering properties of both sugar maple (Acer saccarum) and eastern cottonwood (Populus deltoides) leaves in the near-IR wavelength regime. The bidirectional scattering distribution function (BSDF) describes the fractions of light reflected by and transmitted through a leaf for a given set of illumination and observation angles. Experiments were performed to measure the BSDF of each species at a discrete set of illumination and observation angles. We then modeled the BSDFs in such a way that other researchers may interpolate their values for scattering in any direction under illumination at any angle.     

Orthogonal Light-Dependent Membrane Adhesion Induces Social Self-Sorting and Member-Specific DNA Communication in Synthetic Cell Communities

Developing orthogonal chemical communication pathways in diverse synthetic cell communities is a considerable challenge due to the increased crosstalk and interference associated with large numbers of different types of sender-receiver pairs. Herein, the authors control which sender-receiver pairs communicate in a three-membered community of synthetic cells through red and blue light illumination. Semipermeable protein-polymer-based synthetic cells (proteinosomes) with complementary membrane-attached protein adhesion communicate through single-stranded DNA oligomers and synergistically process biochemical information within a community consisting of one sender and two different receiver populations. Different pairs of red and blue light-responsive protein-protein interactions act as membrane adhesion mediators between the sender and receivers such that they self-assemble and socially self-sort into different multicellular structures under red and blue light. Consequently, distinct sender-receiver pairs come into the signaling range depending on the light illumination and are able to communicate specifically without activation of the other receiver population. Overall, this work shows how photoswitchable membrane adhesion gives rise to different self-sorting protocell patterns that mediate member-specific DNA-based communication in ternary populations of synthetic cells and provides a step towards the design of orthogonal chemical communication networks in diverse communities of synthetic cells.     

Double-groove, two-depth grating coupler for light guides

A double-groove, two-depth dielectric grating structure for high-efficiency light coupling into a light guide is introduced. We show computationally that the optimized gratings can couple a monochromatic TE- or TM-polarized light beam with nearly 100% efficiency. For an unpolarized light beam 90% efficiency can be reached. In all cases the highest achieved coupling efficiencies require that the refractive index of the grating material be greater than 1.7. The illumination and fabrication tolerances of the couplers are also analyzed.     

Rocket seedling production on the international space station: Growth and nutritional properties

Producing sprouts directly during space missions may represent an interesting opportunity to offer high-quality fresh ready to eat food to the astronauts. The goal of this work was to compare, in terms of growth and nutritional quality, rocket (Eruca sativa Mill.) seedlings grown in the International Space Station during the ENEIDE mission with those grown in a ground-based experiment (in presence and absence of clinorotation). The rocket seedlings obtained from the space-experiment were thinner and more elongated than those obtained in the ground-based experiment. Cotyledons were often closed in the seedlings grown in the space experiment. Quantitative (germination, fresh and dry weight) and qualitative (glucose, fructose, sucrose and starch) traits of rocket seedling were negatively affected by micrograv-ity, especially those recorded on seedlings grown under real microgravity conditions The total chlorophyll, and carotenoids of seedlings obtained in the space experiment were strongly reduced in comparison to those obtained in the ground-based experiment (presence and absence of clinorotation). The results showed that it is possible to produce rocket seedlings in the ISS; however, further studies are needed to define the optimal environmental conditions for producing rocket seedlings with high nutritional value