Entrainment of the larval release rhythm of the crab Rhithropanopeus harrisii (Brachyura: Xanthidae) by cycles in hydrostatic pressure

This study investigated the entrainment of a larval release rhythm by determining whether a tidal cycle in hydrostatic pressure could entrain the circatidal rhythm in larval release by the crab Rhithropanopeus harrisii (Gould). Ovigerous females were collected from a non-tidal estuary. The time of larval release by individual crabs was monitored under constant conditions with a time-lapse video system. Crabs with mature embryos at the time of collection had a pronounced circadian rhythm in larval release with a free running period of 25.1 h. Crabs with immature embryos that were maintained under constant conditions from the time of collection until larval release retained a weak circadian rhythm. Other crabs with immature embryos were exposed to a tidal cycle in step changes in hydrostatic pressure equivalent to 1 m of water. This cycle entrained a circatidal rhythm in larval release. The free-running period was 12.1 h and larvae were released at the time of the transition from low to high pressure. Although past studies demonstrated that a tidal cycle in hydrostatic pressure could entrain activity rhythms in crustaceans, this is the first study to show that pressure can entrain a larval release rhythm.     

Comparative measurements of the xylem pressure ofNicotiana plants by means of the pressure bomb and pressure probe

Determination of the pressure in the water-conducting vessels of intactNicotiana rustica L. plants showed that the pressure probe technique gave less-negative values than the Scholander-bomb method. Even though absolute values of the order of −0.1 MPa could be directly recorded in the xylem by means of the pressure probe, pressures between zero and atmospheric were also frequently found. The data obtained by the pressure probe for excised leaves showed that the Scholander bomb apparently did not read the actual tension in the xylem vessles ofNicotiana plants. The possibility that the pressure probe gave false readings was excluded by several experimental controls. In addition, cavitation and leaks either during the insertion of the microcapillary of the pressure probe, or else during the measurements were easily recognized when they occurred because of the sudden increase of the absolute xylem tension to that of water vapour or to atmospheric, respectively. Tension values of the same order could also be measured by means of the pressure probe in the xylem vessels of pieces of stem cut from leaves and roots under water and clamped at both ends. The magnitude of the absolute tension depended on the osmolarity of the bathing solution which was adjusted by addition of appropriate concentrations of polyethylene glycol. Partial and uniform pressurisation of plant tissues or organs, or of entire plants (by means of the Scholander bomb or of a hyperbaric chamber, respectively) and simultaneous recording of the xylem tension using the pressure probe showed that a 1∶1 response in xylem pressure only occurred under a few circumstances. A 1∶1 response required that the xylem vessels were in direct contact with an external water reservoir and/or that the tissue was (pre-)infiltrated with water. Corresponding pressure-probe measurements in isolated vascular bundles ofPlantago major L. orP. lanceolata L. plants attached to a Hepp-type osmometer indicated that the magnitude of the tension in the xylem vessels was determined by the external osmotic pressure of the reservoir. These and other experiments, as well as analysis of the data using classical thermodynamics, indicated that the turgor and the internal osmotic pressure of the accessory cells along the xylem vessels play an important role in the maintenance of a constant xylem tension. This conclusion is consistent with the cohesion theory. In agreement with the literature (P.E. Weatherley, 1976, Philos. Trans. R. Soc. London Ser. B23, 435–444; 1982, Encyclopedia of plant physiology, vol. 12B, 79-109), it was found that the tension in the xylem of intact plants under normal and elevated ambient pressure (as measured with the pressure probe) under quasi-stationary conditions was independent of the transpiration rate over a large range, indicating that the conductance of the flow path must be flow-dependent.     

Isolation of biochemical mutants using haploid mesophyll protosplasts of Hyoscyamus muticus

The question of whether membrane expansion, which is caused by anesthetics in animal systems, alters the lipid composition of plant cell membranes was investigated. We have measured the effects of several anesthetics on the relative amounts of the principal fatty acids from the polar lipids of barley (Hordeum vulgare L.) root membranes. Procaine, dibucaine, tetracaine, chloroform and, to a lesser degree, methanol increased the proportions of palmitic, stearic and oleic acids and decreased the proportions of linoleic and linolenic acids. Ethanol had no significant effect. Total amounts of the fatty acids from the polar lipids of roots in procaine solution decreased markedly so that all of the acids decreased in amount. The anesthetic was effective as soon as the roots were introduced to the solution and the changes progressed at constant rates for 6 h. Only the polar membrane lipids were altered; other lipids were not affected. Increased hydrostatic pressure of about 1.0 MPa largely prevented the anesthetic effects, including the decrease in the total amounts of the fatty acids. Hydrostatic pressure as high as 2 MPa had no effect per se on the membrane lipid composition. These results indicate that anesthetics cause expansion of the root membranes which results in the lipid changes. That a compositional change in the membrane lipids involves a conformational change such as expansion is an indication of the nature of the link between changes in the membrane lipids and changes in function of areas where hydrophilic ions permeate.Abbreviations 16:0 palmitic acid - 18:0 stearic acid - 18:1 oleic acid - 18:2 linoleic acid - 18:3 linolenic acid     

Growth increment ofAlnus glutinosa upon dual inoculation with effective and ineffectiveFrankia strains

Investigations on the ecological function of ineffectiveFrankia strains and their behaviour in competition with effectiveFrankia strains indicated an enhanced plant growth upon dual inoculation with increasing amounts of effective (i.e. N₂-fixing)Frankia strains and simultaneous inoculation with a constant amount of an ineffectiveFrankia strain. Enhanced plant growth was measured as increase in plant height and total dry weight at constant shoot/root ratio. The stimulating effect of the ineffective strain was independent of the plant clone and was obtained with bothAlnus glutinosa clones W I and B II, which were resistant and susceptable, respectively, to the ineffective strain. Stimulation was also independent of the nodulation conditions. Short-term studies (7 weeks) under axenic conditions and greenhouse experiments during 3 months showed comparable results, not only in plant growth but also in nodule formation. Increment in plant growth was not necessarily correlated to higher nodule formation with the effectiveFrankia strains.     

Dynamics of CO2 evolution by plants at low pressure

Dynamics of CO₂ evolution at low pressure was studied in barley, maize, pea, wheat and pine seedlings using the gas exchange system with laser photoacoustic spectrometer. The CO₂ evolution from plant surfaces to environment increased with decreasing air pressure. Simultaneously the changes in activities of phosphoenolpyruvate carboxylase, glucose-6-phosphate dehydrogenase, glyceraldehyde phosphate dehydrogenase, alcohol-dehydrogenase, isocitrate dehydrogenase, malate dehydrogenase in pea and maize leaves were observed. The response depended on plant species used as well as on air pressure and period of its action     

The Release of Extrinsic Polypeptides and Manganese Cluster from Photosystem 2 Membranes under High Hydrostatic Pressure

Three extrinsic polypeptides and manganese cluster were sequentially released from the membrane when photosystem 2 (PS2) membranes were kept under high hydrostatic pressure. The 17 kDa polypeptide was the most sensitive, while the 33 kDa polypeptide was the most reluctant to the treatment with high pressure. The release of manganese was not simply correlated with the loss of 33 kDa polypeptide. The losing of oxygen-evolving activity of PS2 was synchronised with the releasing of extrinsic polypeptides and manganese.     

Shell nacre ultrastructure and depressurisation dissolution in the deep-sea hydrothermal vent mussel Bathymodiolus azoricus

This study describes the micro-morphological features of the shell nacre in the vent mytilid Bathymodiolus azoricus collected along a bathymetric gradient of deep-sea hydrothermal vents of the mid-Atlantic ridge (MAR). Pressure-dependent crystallisation patterns were detected in animals subjected to post-capture hydrostatic simulations. We provide evidence for the following: (1) shell micro morphology in B. azoricus is similar to that of several vent and cold-seep species, but the prismatic shell layers may vary among bathymodiolids; (2) nacre micro-morphology of mussels from three vent sites of the MAR did not differ significantly; minor differences do not appear to be related to hydrostatic pressure, but rather to calcium ion availability; (3) decompression stress may cause drop off in pH of the pallial fluid that damages nascent crystals, and in a more advanced phase, the aragonite tablets as well as the continuous layer of mature nacre; and (4) adverse effects of decompression on calcium salt deposition in shells was diminished by re-pressurisation of specimens. The implications of the putative influence of hydrostatic pressure on biomineralisation processes in molluscs are discussed. An erratum to this article can be found at     

Effect of hypobaric conditions on ethylene evolution and growth of lettuce and wheat

Elevated levels of ethylene occur in enclosed crop production systems and in spaceflight environments, leading to adverse plant growth and sterility. There are engineering advantages in growing plants at hypobaric (reduced atmospheric pressure) conditions in biomass production for extraterrestrial base or spaceflight environments. Objectives of this research were to characterize the influence of hypobaria on growth and ethylene evolution of lettuce (Lactuca sativa) and wheat (Triticum aestivum). Plants were grown under variable total gas pressures [from 30 to 101 kPa (ambient)]. In one study, lettuce and wheat were direct seeded, germinated and grown in the same chambers for 28 d at 50 or 101 kPa. Hypobaria increased plant growth and did not alter germination rate. During a 10-day study, 28-day-old lettuce and 40-day-old wheat seedlings were transplanted together in the same low and ambient pressure chambers; ethylene accumulated in the chambers, but the rate of production by both lettuce and wheat was reduced more than 65% under 30 kPa compared with ambient pressure (101 kPa). Low O2 concentrations [partial pressure of O2 (pO2) = 6.2 kPa] inhibited ethylene production by lettuce under both low (30 kPa) and ambient pressure, whereas ethylene production by wheat was inhibited at low pressure but not low O2 concentration. There was a negative linear correlation between increasing ethylene concentration and decreasing chlorophyll content of lettuce and wheat. Lettuce had higher production of ethylene and showed greater sensitivity to ethylene than wheat. The hypobaric effect on reduced ethylene production was greater than that of just hypoxia (low oxygen).     

Ripe pollen carbohydrate changes in Trachycarpus fortunei: the effect of relative humidity

Pollen of the palm Trachycarpus fortunei was kept at 25°C and relative humidities (RH) of 20, 55 and 98%. Changes in viability, water content and carbohydrates were measured over 2–17 days. Water content remained almost constant at 20 and 50% RH and increased dramatically at 98%. Pollen viability and germination rate remained almost constant over 14 days at 20% RH and decreased to about 2% after 7–9 days at 55% and to even less at 98% RH. Although the three experimental conditions were constant, qualitative and quantitative variations in pollen carbohydrates were recorded, even after pollen had lost its viability. The quantities of mono-, di- and polysaccharides varied with the period of pollen storage at the various RH. The greatest changes in glucose, fructose and sucrose content were recorded at 55 and 98% RH. At these relative humidities, maximum glucose and fructose content and minimum sucrose content occurred at maximum water content. Starch was not present in mature pollen but appeared and peaked after 7–9 days of pollen storage at 55 and 98%. Appearance of starch coincided with an increase in pectin content. PAS-positive cytoplasmic polysaccharides showed an increasing trend at 20% RH. A relation was found between pollen viability, water content and monosaccharide content. Pollen viability and germination capacity remained high at 20% RH for 14 days. At this relative humidity, pollen water, glucose and fructose contents remained almost constant, while sucrose reached its maximum value. The fluctuations of more complex carbohydrates (starch, pectins and PAS-positive cytoplasmic polysaccharides) were less easy to interpret. Changes observed under experimental conditions could simulate processes occurring in nature during pollen presentation and dispersal.     

Polyhydric alcohol protective effect on Rhizomucor miehei lipase deactivation enhanced by pressure and temperature treatment

The influence of polyhydric alcohols (sorbitol, xylitol, erythritol, glycerol) on the thermal stability of Rhizomucor miehei lipase has been studied at high hydrostatic pressure (up to 500 MPa). In the absence of additives, a protective effect (PE) (the ratio between the residual activities determined at 480 MPa for the enzyme in the presence or absence of polyhydric alcohols) of low-applied pressures (from 50 MPa to 350 MPa) against thermal deactivations (at 50°C and 55°C) has been noticed. In the presence of additives, a strong correlation between PE and the total hydroxyl group concentration has been obtained, for the first time, under treatments of combining denaturing temperatures and high hydrostatic pressures. This relationship does not seem to be dependent on the nature polyhydric alcohols as the same effect could be observed with 1 M sorbitol and 2 M glycerol. This PE, against thermal and high pressure combined lipase deactivation, increases with polyhydric alcohol concentrations, and when temperature increases from 25°C to 55°C.     

The effect of daily exposure to low hardening temperature on plant vital activity

Phenomenological responses of plants to daily short-term exposure to low hardening temperature was studied under chamber and field conditions. Experiments were carried out on cucumber (Cucumis sativus L.), barley (Hordeum vulgare L.), marigolds (Tagetes L.), and petunia (Petunia × hybrida) plants. The obtained data demonstrated a similar pattern of response in all studied plant species to different variants of exposure to low hardening temperature. The main features of plant response to daily short-term exposure to low hardening temperature include: a higher increment in cold tolerance (cf. two-or threefold increase relative to constant low hardening temperature) that peaked on day 5 (cf. day 2 at constant low hardening temperature) and was maintained for 2 weeks (cf. 3–4 days at constant low hardening temperature); a simultaneous increase in heat tolerance (cf. twofold relative to constant low hardening temperature) maintained over a long period (cf. only in the beginning of the exposure to constant low hardening temperature); a sharp drop in the subsequent cold tolerance after plant incubation in the dark (cf. a very low decrease in cold tolerance following the exposure to constant low hardening temperature); a combination of high cold tolerance and high photochemical activity of the photosynthetic apparatus (cf. a low non-photochemical quenching at constant low hardening temperature); and the capacity to increase cold tolerance in response to repeated short-term exposures to low hardening temperature in plants grown outdoors (cf. a gradual increase after repeated exposure to constant low hardening temperature). Possible mechanisms underlying the plant response to daily short-term exposure to low temperature are proposed.     

Hydrostatic pressure mimics gravitational pressure in characean cells

Summary Hydrostatic pressure applied to one end of a horizontalChara cell induces a polarity of cytoplasmic streaming, thus mimicking the effect of gravity. A positive hydrostatic pressure induces a more rapid streaming away from the applied pressure and a slower streaming toward the applied pressure. In contrast, a negative pressure induces a more rapid streaming toward and a slower streaming away from the applied pressure. Both the hydrostatic pressure-induced and gravity-induced polarity of cytoplasmic streaming respond identically to cell ligation, UV microbeam irradiation, external Ca²⁺ concentrations, osmotic pressure, neutral red, TEA Cl^–, and the Ca²⁺ channel blockers nifedipine and LaCl₃. In addition, hydrostatic pressure applied to the bottom of a vertically-oriented cell can abolish and even reverse the gravity-induced polarity of cytoplasmic streaming. These data indicate that both gravity and hydrostatic pressure act at the same point of the signal transduction chain leading to the induction of a polarity of cytoplasmic streaming and support the hypothesis that characean cells respond to gravity by sensing a gravity-induced pressure differential between the cell ends.     

Relative importance of fertiliser addition to plants and exclusion of predators for aphid growth in the field

Herbivore dynamics and community structure are influenced both by plant quality and the actions of natural enemies. A factorial experiment manipulating both higher and lower trophic levels was designed to explore the determinants of colony growth of the aphid Aphis jacobaeae, a specialist herbivore on ragwort Senecio jacobaea. Potential plant quality was manipulated by regular addition of NPK-fertiliser and predator pressure was reduced by interception traps; the experiment was carried out at two sites. The size and persistence of aphid colonies were measured. Fertiliser addition affected plant growth in only one site, but never had a measurable effect on aphid colony growth. In both habitats the action of insect predators dominated, imposing strong and negative effects on aphid colony performance. Ants were left unmanipulated in both sites and their performance on the aphid colonies did not significantly differ between sites or between treatments. Our results suggest that, at least for aphid herbivores on S. jacobaea, the action of generalist insect predators appears to be the dominant factor affecting colony performance and can under certain conditions even improve plant productivity.     

Adaptation of Saccharomyces cerevisiae to high hydrostatic pressure causing growth inhibition

Genome-wide mRNA expression profiles of Saccharomyces cerevisiae growing under hydrostatic pressure were characterized. We selected a hydrostatic pressure of 30 MPa at 25 degrees C because yeast cells were able to grow under these conditions, while cell size and complexity were increased after decompression. Functional characterization of pressure-induced genes suggests that genes involved in protein metabolism and membrane metabolism were induced. The response to 30 MPa was significantly different from that observed under lethal conditions because protein degradation was not activated under 30 MPa pressure. Strongly induced genes those that contribute to membrane metabolism and which are also induced by detergents, oils, and membrane stabilizers.     

Effects of the actin-binding protein DNAase I on cytoplasmic streaming and ultrastructure of Amoeba proteus

Microinjection of DNAase I, which is known to form a specific complex with G-actin, induces characteristic changes in cytoplasmic streaming, locomotion and morphology of the contractile apparatus of A. proteus. Light microscopical studies show pronounced streaming originating from the uroid and/or the retracting pseudopods, which ceases 10--15 min after injection of DNAase I, at a time when ultrasctructural studies show that the actin filament system is very much reduced. These results suggest that a controlled reversible equilibrium between soluble and polymerized forms of actin is a necessary requirement for amoeboid movement. The topographic distribution of contractile filaments beneath the plasma membrane visualized by correlated light- and electron microscopy of DNAase I-injected cells establishes the importance of the membrane-bound filamentous layer for three major aspects of streaming: (1) Streaming originates by local contractions of a cell membrane-associated filament layer at the uroid and/or retracting pseudopods, creating a pressure flow. (2) This flow continues beneath the membrane, which is stabilized by filaments in the lateral regions between the posterior end, with a high hydrostatic pressure, and the anterior end, with a low hydrostatic pressure. (3) Pseudopods or extending areas are created by a local destabilization of the cell periphery caused by the separation of the filamentous layer from the plasma membrane.     

Structural phase transition of SnSe under uniaxial stress and hydrostatic pressure: an ab initio study

We study the structural behavior of SnSe under the hydrostatic pressure using a constant pressure ab initio technique. We find SnSe undergoes a structural second order phase transition from the orthorhombic (Pnma) structure to orthorhombic (Cmcm) structure in the constant pressure simulation at 7 GPa which is in good agreement with the recent experimental study. The Cmcm structure is fivefold coordinated. This phase transition is also analyzed from the total energy calculations. Besides, we study the behavior of SnSe under uniaxial stress.     

Effects of cyclic and constant hydrostatic pressure on norepinephrine and epinephrine levels in the brain of flounder

The effects of cyclic and constant hydrostatic pressure on the norepinephrine and epinephrine content in discrete regions of the brain of European flounder Platichthys flesus were studied. After a 14 day exposure to cyclic hydrostatic pressure with a tidal period of 12·4 h and with a maximum peak of 800 kPa (range 200–800 kPa of absolute hydrostatic pressure), fish showed a highly significant decrease in norepinephrine content when compared to control animals held at constant atmospheric pressure. No changes were detected in fish submitted to a constant hydrostatic pressure of 800 kPa.     

Hydrostatic pressure regulates tight junctions, actin cytoskeleton and transcellular ion transport

In the epithelia and endothelia, tight junctions regulate the movement of several substances through the paracellular pathway, maintaining several gradients between apical and basal compartments including osmolality and hydrostatic pressure. In this study, we show that the change of hydrostatic pressure gradient affected tight junctions as well as actin cytoskeleton, cell height and transcellular ion transport. Hydrostatic pressure gradient from basolateral to apical side increased transepithelial conductance and altered claudin-1 localization within several tens of minutes. These changes were promptly restored by the elimination of hydrostatic pressure gradient. Hydrostatic pressure gradient also induced dynamic changes in the actin structure and cell height. We further found that hydrostatic pressure gradient from basolateral to apical side stimulates transcellular Cl⁻ transport. Our present findings indicate that the epithelial cell structures and functions are regulated by the hydrostatic pressure gradient which is generated and maintained by the epithelia themselves.     

Growth,nitrogen fixation and relative efficiency of nitrogenase inAlnus incana grown in different cultivation systems

Summary Three cultivation systems were compared. In one system the alders were grown hydroponically. In the two other systems the alders were planted in gravel and either given water and nutrients at intervals or the nutrient solution was continuously supplied. Alders continuously supplied with nutrients and water showed a significantly more rapid growth, higher biomass production and higher nitrogen content than did alders given nutrients and water at intervals or alders hydroponically grown. Alders continuously supplied with water and nutrients had a constant RE (relative efficiency of nitrogenase) of about 0.80 throughout the experimental period while alders supplied with water and nutrients at intervals showed a slight decrease in RE at the end of the experimental period. No strict relationship was found between RE and nitrogen content or between RE and plant productivity.     

来源于超嗜热古菌雅氏火球菌(Pyrococcus yayanosii)CH1耐热耐压脯肽酶的酶学性质研究

【目的】脯肽酶是一种能从二肽(Xaa-Pro)的C末端水解脯氨酸或羟脯氨酸残基的肽酶。对深海来源的雅氏火球菌(Pyrococcus yayanosii) CH1基因组中PYCH_07700基因编码的蛋白Pyprol的体外酶学性质进行研究,以期发现新型脯肽酶。【方法】在小宝岛热球菌(Thermococcus kodakarensis) TS559中异源表达Pyprol。使用二肽Met-Pro作为底物,检测重组蛋白的脯肽酶活性。【结果】Pyprol的最适温度为100 ℃,最适pH为6.0。Pyprol在与Co²⁺结合时活性最高,最适的金属离子浓度为1.2 mmol/L。与P. furiosus来源的脯肽酶Pfprol相比,Pyprol在更宽的pH范围具有活性,并且能够耐受更高浓度的金属离子。Pyprol是耐压蛋白,最适静水压为40 MPa。与常压条件下相比,40 MPa下,Pyprol在40、70和100 ℃均有更高的活性。【结论】来源于深海热液喷口的严格嗜压的超嗜热古菌P. yayanosii CH1的新型脯肽酶Pyprol具有热稳定和耐压特性。