Photosynthesis of isolated chloroplasts and protoplasts under osmotic stress

1. Isolated intact spinach chloroplasts respond to changes of the sorbitol concentration of the suspending medium as near-perfect osmometers within a large range of osmotic potentials. Under isotonic conditions (=9–10 bar), their average osmotic volume is 24 m³ and the total volume 36 m³. The osmotic volume can be increased to 63 m³ by lowering the sorbitol concentration until a critical osmotic potential of =4 bar is reached. Below that value chloroplasts rupture. Between 10 bar and 4 bar, volume changes are reversible. 2. Increasing the chloroplast volume above 24 m³ causes inhibition of photosynthesis, with 50% inhibition occurring at an osmotic potential of =5–6 bar. This corresponds to an osmotic volume of 45–55 m³. Depending on the duration of hypotonic treatment, inhibition of photosynthesis is more or less reversible. 3. Between 4 and 10 bar, the chloroplast envelope exhibits a very low permeability for ferricyanide, many metabolites, and soluble stroma proteins. 4. Electron transport is not inhibited by swelling of chloroplasts. Also, the ATP/ADP-ratio remains unchanged. 5. The solute concentration in the chloroplasts appears to be optimal for photosynthesis at 10 bar. Increasing the chloroplast volume causes inhibition of photosynthesis by dilution effects.     

Effects of satiation on feeding and swimming behaviour of planktivores

Hunger affects the feeding and swimming behaviour in fish. After 36 h of food deprivation, the feeding and swimming behaviour of Pseudorasbora parva (Cyprinidae) was studied under different prey densities (0.5, 1, 2, 5, 10 and 25 of Daphnia pulex per liter). The initial feeding rates showed marked variations in relation to prey availability. Under high prey densities, the initial feeding rate of fish was higher and subsequently decreased faster, when compared to those feeding under low prey densities. At higher prey densities, two factors were involved: that of higher prey encounter rates and also the attainment of food satiation at a faster rate. Across all prey densities, the feeding rates of fish reached a plateau after satiation. The swimming speed of fish was found to be negatively related to the prey density and a significant change in swimming speed was noted as being directly related to the level of satiation. It was found that the increasing satiation level greatly influenced the handling time and reactive volume of predator, which finally caused reduced feeding rates.     

Determination of intracellular volume and internal solute concentrations of the green alga Chlorococcum submarinum

A method is described for measuring the cell volume of the unicellular green alga Chlorococcum submarinum, which depends on measurements of bromide concentration before and after disruption of the cells by ammonium hydroxide. Simultaneous equations are derived, which along with direct determination of cell water weight, allow the calculation of the intracellular volume in three different ways. The volumes calculated are in agreement indicating the validity of the method. The cell volumes and internal concentrations of glycerol, proline, potassium and sodium were determined for algae adapted to three salinities, 0.1, 0.5 and 1.0 M NaCl. The results showed that glycerol was the major internal solute and that the total measured solutes balanced the external osmotic pressure at all three salinities.Abbreviations DMSO dimethyl sulphoxide - Hepes N-[2-hydroxyethyl]piperazine-N-2-ethane sulfonic acid - TCA trichloroacetic acid - Tris tris[hydroxymethyl]aminoethane     

Allozyme variation in populations, full-sib families and selfed lines in Betula pendula Roth

Changes in genetic variability in populations (stand origins), full-sib (FS) families and three generations of selfed lines of Betula pendula were observed based on 15 allozyme loci. Growth vigour, measured as stem volume, and its relationship with heterozygosity was studied to determine the effect of inbreeding. Pooled FS families showed a higher percentage of polymorphic loci (P) and allelic numbers per locus (A) than those of natural populations, but no difference in heterozygosity. There was no difference in allozyme variability between fast-and slow-growing family groups, and heterozygosity was not correlated with stem volume among FS families. Allozyme variability was significantly decreased in advancing generations of selfing, and the further the selfing generation, the lower the heterozygosity and the slower the growth. Observed heterozygosity after advancing generations of inbreeding was increasingly higher than expected, indicating overdominance effects or, alternatively, selection against deleterious homozygotes.     

Physiological properties and cytological features of protoplasts prepared fromChlorella saccharophila

Summary Protoplasts were prepared from cells ofChlorella saccharophila by treatment with a mixture of pectinase and cellulase. The yield of protoplasts is dependent upon the culture conditions prior to cell wall digestion. In thin section chemically-fixed protoplasts were without wall remnants at the surface of the plasma membrane. Of particular interest is the relationship between the Golgi apparatus and a nuclear envelope-endoplasmic reticulum continuum. Protoplasts have a photosynthetic capacity lying between 70 and 80% of that of normal cells, but show the same response towards CO₂ concentration and DCMU inhibition. Protoplasts also respond to changes in the osmolarity of the surrounding medium in accordance with the Boylevan't Hoff equation as if they are an osmometer. The nonosmotic volume (NOV) was calculated.Abbreviations GA Golgi apparatus - ER endoplasmic reticulum - NE nuclear envelope - PM plasma membrane - N nucleus - S starch - M mitochondria - V vacuole     

Growth of dinoflagellates, Ceratium furca and Ceratium fusus in Sagami Bay, Japan: The role of vertical migration and cell division

To better understand the mechanism underlying the bloom outbreaks of dinoflagellates, Ceratium furca, and Ceratium fusus in the temperate coastal area of Sagami Bay, we investigated the diel changes of vertical migration, swimming speed, cell volume, and cell division. Our results from both the field and laboratory indicate that C. furca and C. fusus can migrate vertically between surface and sub-surface layers to avoid strong sunlight (>1000 μmol m⁻² s⁻¹). Diel vertical migration (DVM) of C. furca was observed in the laboratory, while that of C. fusus was not observed. C. furca demonstrated a constant DVM rhythm, i.e., their cells began to descend from the surface before the light was extinguished, and ascended into the surface before the light was turned on. The downward and upward migrations of the cells occurred at every 3 h before turning on and off the light, suggesting that the DVM pattern was independent of nutrient concentration. The swimming speeds of C. furca (avg. 250 μm s⁻¹) were always faster than those of C. fusus (avg. 75 μm s⁻¹). In addition, the speeds of C. furca during light periods were faster than those during dark periods, whereas the speeds of C. fusus remained relatively constant. A higher proportion of dividing cells was recorded near dawn (05:00–07:00 h). Cell volumes of C. furca and C. fusus did not markedly change between 12:00 and 21:00 h, but gradually increased until 03:00 h and then sharply decreased. Furthermore, the cell volume of the two Ceratium species was significantly shifted to the temporal pattern of cell division. Combined with the DVM manner of two Ceratium and cell division timing, only C. furca divided at the bottom, and then moved toward the surface shortly before the dark to light transition. Based on our observations, C. furca has an ecological advantage due to their DVM activity, since nutrients can be obtained well in the near bottom layers, while during the daytime, light present in nutrient-depleted surface water can be obtained using their high swimming speed. On the other hand, C. fusus stimulated by low salinity conditions, might be dependent on external environmental conditions such as additional nutrients following freshwater discharge by heavy rainfall because they may not perform active DVM due to a slow swimming ability. Our findings support that specific characteristics, including the DVM behavior in C. furca, yield a competitive advantage over C. fusus in Sagami Bay.     

Population variation in plant traits associated with ant attraction and herbivory in Chamaecrista fasciculata (Fabaceae)

The benefits of ant–plant–herbivore interactions for the plant depend on the abundance of ants and herbivores and the selective pressures these arthropods exert. In plants bearing extrafloral nectaries (EFN), different mean trait values may be selected for by different populations in response to local herbivore pressure, ultimately resulting in the evolution of differences in plant traits that attract ants as defensive agents against herbivory. To determine if variation in traits that mediate ant–plant interactions reflect herbivore selective pressures, we quantified intra- and inter-population variation in plant traits for eight populations of the EFN-bearing annual Chamaecrista fasciculata (Michx.) (Fabaceae). Censuses in rural and urban areas of Missouri and Illinois (USA) showed population differences in ant attendance and herbivore pressure. Seeds were collected from each population, and plants were grown in a common greenhouse environment to measure sugar production, nectar volume and composition, EFN size and time of emergence, leaf pubescence, and leaf quality throughout plant development. Populations varied mainly in terms of nectary size, sugar production, and nectar volume, but to a lesser degree in leaf pubescence. Populations of C. fasciculata within urban areas (low in insect abundance) had small nectaries and the lowest nectar production. There was a positive correlation across populations between herbivore density and leaf damage by those herbivores on the one hand and sugar production and nectar volume on the other. These results, in conjunction with lack of evidence for maternally based environmental effects, suggest that population differences in herbivore damage have promoted differential evolution of EFN-related traits among populations. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Leaf water relations characteristics of Lupinus angustifolius and L. cosentinii

Summary Lupins (Lupinus angustifolius and L. cosentinii) growing in 321 containers in a glasshouse were exposed to drought by withholding water. Leaf water potential (₁), and leaf osmotic potential (_s) were measured daily as soil water became depleted. Leaf water relations were further assessed by a pressure-volume technique and by measuring _s and relative water content of leaves after rehydration. Analysis by pressure-volume or cryoscopic techniques showed that leaf osmotic potential at saturation (_s100) decreased from -0.6 MPa in well watered to -0.9 MPa in severely droughted leaves, and leaf water potential at zero turgor (_zt) decreased from about -0.7 to -1.1 MPa in well watered and droughted plants, respectively. Relative water content at zero turgor (RWC_zt) was high (88%) and tended to be decreased by drought. The ratio of turgid leaf weight to dry weight was not influenced by drought and was high at about 8.0. The bulk elastic modulus () was approximately halved by drought when related to leaf turgor potential (_p) and probably mediated turgor maintenance during drought. The latter was found to be negatively influenced by rate of drought. Supplying the plants with high levels of K salts did not promote adjustment or turgor maintenance.     

The triggering effect of surfaces and surfactants on heat output,oxygen consumption and size reduction of a starving marine Vibrio

The marine Vibrio DW1 exhibited a positive response in heat output to a dialysis membrane surface in the presence of substrate (100 mM sodium glutamate) and, more particularly, in the absence of exogenous substrate (starvation conditions). The latter result paralleled the previously reported decrease in cell volume and increase in oxygen consumption by starving bacteria at a similar surface. Modified Morita's salts (MMS) did not extract nutrients from the dialysis membrane, but an artificial seawater containing tris buffer (ASW-tris) did extract surface active and nutrient materials from the membrane. The ASW-tris membrane extract and a commercial surfactant, Tween 85, were found to mimic the effects of the dialysis membrane surface by inducing a decrease in cell volume, and an increasing oxygen consumption and heat output of Vibrio DW1 even in the bulk liquid. The significance of the adsorption of naturally occurring surfactants at surfaces in relation to the behaviour of bacteria at the surfaces is discussed.Abbreviations ASW artificial seawater - MMS modified Morita's salts - NMMS nutrient modified Morita's salts - MMSG MMS plus 100 mM sodium glutamate     

Swelling-activated Chloride and Potassium Conductance in Primary Cultures of Mouse Proximal Tubules. Implication of KCNE1 Protein

Volume-sensitive chloride and potassium currents were studied, using the whole-cell clamp technique, in cultured wild-type mouse proximal convoluted tubule (PCT) epithelial cells and compared with those measured in PCT cells from null mutant kcne1 –/– mice. In wild-type PCT cells in primary culture, a Cl^– conductance activated by cell swelling was identified. The initial current exhibited an outwardly rectifying current-voltage (I-V) relationship, whereas steady-state current showed decay at depolarized membrane potentials. The ion selectivity was I^– > Br^– > Cl^– >> gluconate. This conductance was sensitive to 1 mM 4,4-Diisothiocyanostilbene-2,2-disulfonic acid (DIDS), 0.1 mM 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB) and 1 mM diphenylamine-2-carboxylate (DPC). Osmotic stress also activated K⁺ currents. These currents are time-independent, activated at depolarized potentials, and inhibited by 0.5 mM quinidine, 5 mM barium, and 10 µM clofilium but are insensitive to 1 mM tetraethylammonium (TEA), 10 nM charybdotoxin (CTX), and 10 µM 293B. In contrast, the null mutation of kcne1 completely impaired volume-sensitive chloride and potassium currents in PCT. The transitory transfection of kcne1 restores both Cl^– and K⁺ swelling-activated currents, confirming the implication of KCNE1 protein in the cell-volume regulation in PCT cells in primary cultures.     

Improvement of the cell volume ofCandida blankii through protoplast fusion

Summary The yeastCandida blankii ESP-94, capable of utilizing xylose as substrate, was isolated for the production of single-cell protein (SCP) on bagasse hydrolysates. However, the small cell volume of strain ESP-94 would complicate harvesting of the cells during a continuous fermentation process. Auxotrophic mutants of strain ESP-94 were generated and intraspecific protoplast fusion experiments performed in an attempt to increase the cell volume of strain ESP-94. The fusion products were characterised with respect to cell volume, DNA content and genetic stability. Six genetically stable fusants with bigger cell volumes and higher DNA contents were obtained. One such fusant, fusant F17, had a cell volume 3-times that of strain ESP-94, while exhibiting similar growth rates to strain ESP-94 ond-xylose as carbon source.     

Surface areas,lengths and volumes of Picea abies (L.) Karst. needles: determination,biological variability and effect of environmental factors

Summary A method for the rapid determination of the lengths and surface areas of very large samples of needles of Picea abies (L.) Karst. using a computer-aided image analysis system was developed. Two independent methods for measuring non-destructively the volumes of individual needles and of all needles attached to a twig were devised. The surface areas and lengths of about 38000 needles sampled from the three youngest needle age-classes (1986, 1985, 1984) of 48 trees approximately 130 years old at four sites in the Fichtelgebirge mountains (N. E. Bavaria, FRG) were measured. The frequency distributions of lengths and areas for each site and age-class are given. Variability of needle size was fairly large. Even though the sites differed in climate, soil, and air pollution levels no consistent effect of these factors on needle size could be detected. Needle lengths and surface areas did not correlate with either the total chlorophyll content of the needles or the degree of crown thinning. The needle surface area (in mm²) of fully developed P. abies needles can be estimated by the empirical equation surface area = 4.440 x needle length -24.8 (r = 0.937), and the needle volume (in mm³) by needle volume = 0.208 x projected needle area ^1.353 (r = 0.969).     

The use of Artemia biomass sampling to predict cyst yields in culture ponds

The possibility of using biomass volume (= mean biomass present in the pond.week ^–1) to predict the total amount of harvestable cysts (= kg wet weight collected. week ^–1) produced in a culture pond by an Artemia franciscana population using a mixed model regression was evaluated for two different sampling methods; horizontal transects and vertical point samples. For transects, the following equation was found: `log (0.01 + cyst yields) = –2.05 + 0.025<sup>*</sup>(biomass volume)' with F <sub>(1, 4.87)</sub> = 8.83 and p = 0.032. For the point samples, the regression was also significant with F <sub>(1, 55.2)</sub> = 13.62 and p = 0.0005 for following equation: `log (0.01 + cyst yield) = –3.613 + 0.021^*(biomass volume). As pond effect and interaction terms did not significantly explain a significant portion of the variance for either of the sampling methods (Transects: pond: F _{(3, 14.3)} = 2.48; p = 0.103; pond^*biomass volume: F _{(3, 3.61)} = 4.63; p = 0.0976; Point samples: pond: F _{(3, 44.5)} = 0.00; p = 0.999; pond^*biomass volume: F _{(3, 44.2)} = 0.11; p = 0.954 ), the variable pond (repeated measurement factor) was not included in the final calculations for the regression equations. Although a combination of factors influences the equation, the high significance levels of the regression indicate biomass volume can be safely used to predict production trends. The low investment requirements of this method make it especially attractive for on farm use, where correctly determining the point of cyst decline will help farmers to allocate resources where needed.     

Influence of sulfur accumulation and composition of sulfur globule on cell volume and buoyant density of Chromatium vinosum

Average cell volume and cell buoyant density of Chromatium vinosum DSM 185 growing in sulfide limited continuous cultures, were found to increase with increasing dilution rate. It was found that the increase in buoyant density was mainly a consequence of the accumulation of elemental sulfur. The contribution of other compounds such as protein, bacteriochlorophyll a and glycogen, was almost negligible. It was concluded that the sulfur globule is constituted by at least two fractions, sulfur and an unidentified moiety with a density lower than that of sulfur, probably water.A model was developed to explain the relation between the specific content of sulfur and cell buoyant density. The model also predicts the impact of elemental sulfur on the volume of the cell. It was found that in addition to the accumulation of sulfur the average cell volume also changes with the specific growth rate.In shift-up experiments (sulfur accumulation) the actual phenomena agreed with those predicted by the model, however, this was not so during shift-down (sulfur depletion). It is suggested that this difference is due to the fact that during the shift-down, elemental sulfur and the unidentified moiety are being depleted at different rates.Non-standard abbreviations BChl bacteriochlorophyll - PHB poly--hydroxybutyric acid - D dilution rate - specific growth rate - S _R reservoir concentration of limiting substrate     

Blood volume measurement in baboons: simultaneous estimation of red cell volume and plasma volume

A method is described for frequent sequential blood volume estimation in baboons using 32P for red cell volume measurements and 125I-albumin for simultaneous plasma volume measurements. Values for red cell, plasma, and total blood volumes are reported. Close correlations of the volumes to bodyweight were demonstrated. Circulatory half-lives of the isotopes, determined from disappearance curves, confirmed their suitability for serial measurements in these baboons.     

The influence of poly-β-hydroxybutyrate accumulation on cell volume and buoyant density in alcaligenes eutrophus

Accumulation of poly--hydroxybutyrate (PHB) was studied in Alcaligenes eutrophus strain N9A. Under nitrogen limitation and heterotrophic conditions, the cells accumulated PHB at a rate of 50 fg cell^-1 h^-1. Volume increased from 1.208 to 3.808 m³ and buoyant density from 1.110 to 1.145 pg m^-3 with an increase in PHB from 0 up to 1.699 pg cell^-1. Volume was found to change linearly with PHB content. The changes were due to increases in cell width and not in cell length. PHB explained 93% of the changes in cellular volume. The relationship between density and PHB was hyperbolic. PHB explained 96% of the changes in density. When a mutant strain unable to accumulate PHB was analyzed together with the wild type, the PHB-less mutant and the wild type showed densities of 1.100 pg m^-3 and 1.120 pg m^-3, respectively, in gradients of 65% Percoll. In sucrose gradients, nevertheless, the results were reversed. This discrepancy was explained by the high osmolarity of sucrose which gives artificial results. Thus, we conclude that Percoll is a more suitable medium than sucrose to measure the density of live bacterial cells.Abbreviation PHB poly--hydroxybutyrate     

根域体积限制对芹菜幼苗生长和气体交换及叶绿素荧光参数的影响

以芹菜品种‘皇后’为试材,采用自配育苗基质(柠条粉∶珍珠岩∶蛭石=7∶2∶1体积比),按照不同根域体积(110.07、67.20、39.06、26.82、19.76、12.21、7.28cm3/穴)进行育苗,探索在柠条混配基质条件下不同根域体积水平对芹菜幼苗生长、气体交换和叶绿素荧光动力学诱导曲线的影响,为柠条混配基质条件下设施蔬菜育苗提供科学依据。结果表明:(1)芹菜幼苗株高、叶片数、根长、根系体积、地上部鲜质量、地上部干质量、地下部鲜质量和地下部干质量均随着根域体积的减小而降低;根域体积最大(110.07cm3/穴)时的净光合速率和蒸腾速率分别比根域体积最小(7.28cm3/穴)时高出64.13%和18.87%。(2)气孔导度变化总体随着根域体积的减少而减少,胞间CO2浓度变化总体受根域体积影响不大。(3)根域体积过大(110.07cm3/穴)或偏小(7.28cm3/穴)都会影响PSⅡ光合电子传递,均使得PSⅡ反应中心用于热耗散的能量高于用于电子传递的能量,用于电子传递的量子产额(φEo)、ψo值、单位面积捕获的光能(TRo/CS)和单位面积捕获的光能(TRo/CS)分别在根域体积为25.68、14.34、17.32和19.21cm3/穴时达到最大。研究认为,根域体积限制直接影响着芹菜幼苗气体交换和叶绿素荧光参数的变化,进而影响幼苗的光合作用及生长。     

Characterization of absorption and scattering properties for various yeast strains by time-resolved spectroscopy

An understanding of the optical properties of biological media and cells is essential to the development of noninvasive optical studies of tissues. Unicellular organisms offer a unique opportunity to investigate the factors affecting light propagation, since they can be manipulated in ways impossible for more complex biological samples. In this study, we examined optical absorption and scattering properties of strongly multiple scattering yeast suspensions by means of near-infrared (NIR) time-resolved spectroscopy (TRS) and a sample substitution method. We determined the critical parameters for photon migration by varying the cell organelle content, the cell ploidy, the cell size, and the concentration of suspended cells. The results indicate that the photon absorption is insensitive to cell differentiation and that the cell volume is the primary factor determining light-scattering property.     

枝条覆盖对平茬花棒生长特征和浅层土壤水分的影响

为了综合评价枝条覆盖对不同立地(平地、丘顶、丘间低地)平茬花棒(Hedysarum scoparium)生长特征和浅层土壤水分的影响,以吉兰泰荒漠-绿洲过渡区平茬花棒为研究对象,于2017年4—10月对覆盖与无覆盖平茬花棒物候期、土壤容积含水量、土壤储水量和生长指标等相关指标进行测定。实验结果表明:(1)枝条覆盖有利于平茬花棒提前萌芽,较无覆盖提前5 d以上。(2)枝条覆盖使不同立地平茬花棒生长初期和生长末期0—100 cm土层平均土壤容积含水量增加20.12%以上,且土壤含水量变异系数随土层深度增加变化减缓;土壤储水量在生长初期和生长末期枝条覆盖较无覆盖增加27%以上。(3)枝条覆盖使平茬花棒株高、新生枝数、基径、冠幅较无覆盖增加10.91%以上,同时其生物量鲜重和干重较无覆盖分别增加4.45%—24.17%和3.78%—18.93%。尤其丘间低地平茬花棒生物量增加效果更加明显(P0.05)。但枝条覆盖不能改变平茬花棒生物量分配格局;(4)枝条覆盖和平茬对花棒生长均具有积极作用,枝条覆盖对丘间低地平茬花棒生长促进作用最好。     

Some factors affecting the chloroplast replication in the mossPlagiomnium trichomanes

Summary Some factors affecting the chloroplast replication were studied using the leaf cells of the mossPlagiomnium trichomanes. There was a significant positive correlation between chloroplast number per cell and cell volume in leaves of any developmental stage. However, when the detached leaves were cultured on nutrient agar, it was observed that the chloroplast replication occurred without cell enlargement regardless of the developmental stage of leaves. This implies that cell enlargement is not an essential factor for the chloroplast replication, but one of the environmental factors affecting it. Light is essential for the chloroplast replication which response to the light intensity. In the dark, there was little increase in chloroplast number per cell. With a light intensity of 50 lux, the increase rate of chloroplast number per cell was about half of that with 3,000 lux. Day length also affected significantly the chloroplast replication.