外源水杨酸对低温胁迫下火龙果幼苗的形态及生理效应

为探究外源水杨酸(SA)对低温胁迫下火龙果幼苗形态及生理的影响，该研究以‘紫红龙’火龙果幼苗为材料，将4个不同浓度的SA(0.1、0.3、0.5、0.7 mmol·L^-1)喷施叶片，48 h后4℃低温培养，于第0、第3、第6、第9天观察火龙果幼苗形态及叶片组织结构的变化，并测定叶片相对电导率、丙二醛含量、渗透调节物(可溶性糖、可溶性蛋白、脯氨酸)含量及抗氧化酶(超氧化物歧化酶、过氧化物酶、过氧化氢酶、谷胱甘肽S-转移酶)活性等生理指标。结果表明：(1)低温胁迫下，火龙果幼苗呈现0级、Ⅰ级和Ⅱ级3个冷害等级，SA处理后的火龙果幼苗出现Ⅰ级冷害和Ⅱ级冷害的株数百分率均明显降低。(2)与低温对照相比，SA处理能降低火龙果幼苗叶片相对电导率和丙二醛含量并提高渗透调节物含量和抗氧化酶活性。(3)通过对不同SA处理结果进行比较分析，发现缓解冷害症状、降低相对电导率和丙二醛含量、提高可溶性糖和脯氨酸的含量、提高超氧化物歧化酶和谷胱甘肽S-转移酶的活性均以0.3 mmol·L^-1 SA效果最好，提高可溶性蛋白含量、过氧化物酶活性、过氧化氢酶活性分别以0.7、...     

Effects of substratum morphology on cell physiology

Among the host of substratum properties that affect animal cell behavior, surface morphology has received relatively little attention. The earliest effect of surface morphology on animal cells was discovered almost a century ago when it was found that cells became oriented in response to the underlying topography. This phenomenon is now commonly known as contact guidance. From then until very recentrly, little progress has been made in understanding the role of surface morphology on cell behavior, primarily due to a lack of defined surfaces with uniform morphologies. This problem has been solved recently with the development of photolithographic techniques to prepare substrata with well defined and uniform surface morphologies. Availability of such surfaces has facilitated systematic in vitro experiments to study influence of surface morphology on diverse cell physiological aspects such as adhesion, growth, and function. For example, these studies have shown that surfaces with uniform multipls parallel grooves can enhance cell adhesion by confining cells in grooves and by mechanically interlocking them. Several independent studies have demosterated that cell shape is a major determinant of cell growth and function. Because surface morphology has been shown to modulate the extent of cell spreading and cell shape, its effects on cell growth and function appear to be mediated via this biological coupling between cell shape and function. New evidence in the cell biology literature is emerging to suggest that surface morphology could affect other cell behavioral properties such as post-translational modifications. Further elucidation of such effects will enable better designs for implant and cell culture substrata.     

Effects of low temperature on wheat leaf proteins

Finnish wheat cultivars, winter wheat ‘Vakka’ and spring wheat ‘Apu’, grown for 9 days at 25° and then for 52 days at 2–4°, were called ‘hardened’. Proteins and esterases of young leaves were resolved by polyacrylamide gel electrophoresis (PAGE), porosity gradient PAGE (poroPAGE), isoelectric focusing (PAGIF) between pH 3 and 9, and by Na-dodecylsulfate (SDS)-PAGE. Hardened and unhardened leaves have different protein patterns after PAGE, PAGIF, poroPAGE and SDS-PAGE, respectively, as well as for esterases after PAGE and PAGIF. The PAGIF patterns of esterases show distinct changes of two bands especially for hardened leaves of winter wheat, one appearing, the other one disappearing.     

Effects of cell motility and morphology on the rheology of algae suspensions

Algae have been proposed as a source of biofuels and high value chemical products, but if this potential is to be fully realised, it is crucial to understand the factors affecting the suspension rheology. Suspensions of three algae species, Tetraselmis chuii, Chlorella sp. and Phaeodactylum tricornutum, were sheared in a rotational rheometer in order to characterise their rheology and examine the effects of cell concentration, motility and morphology. The volume fraction ranged from 0.05 to 0.2, and the shear rate from 20 to 200 s^?1. The rheology measurements are fitted to the Herschel-Bulkley model, and the intrinsic viscosity is estimated using both Einstein’s equation and the Krieger-Dougherty model, which are found to perform well for low concentrations. The intrinsic viscosity of T. chuii suspensions is shown not to be constant, but decreases with strain rate, indicating that the suspension viscosity is less sensitive to the cell concentration at high strain rates. The rate of decline is constant for strain rates below approximately 100 s^?1, after which it continues to decline linearly, but at a slower rate. It is speculated that this transition at 100 s^?1 is related to the appearance of flocculation at low strain rates. The effect of the cell motility on the rheology of T. chuii suspensions is investigated by comparing the rheology of motile and passive cells. The shear-thinning behaviour is absent and the effective viscosity is considerably lower for the passive cell suspensions, indicating that the motility of the T. chuii cells causes them to align to resist the flow. In contrast, the Chlorella sp. suspensions exhibit shear-thickening behaviour, which has not previously been reported. Finally, the influence of the effective aspect ratio on the cell suspensions is examined by comparing the intrinsic viscosity of all three species. The algal species with the largest aspect ratio, P. tricornutum, has the largest intrinsic viscosity, while the smallest aspect ratio strain, Chlorella sp., has the smallest viscosity. However, it is shown that the increase in viscosity of motile compared to non-motile T. chuii suspensions cannot be attributed to a change in the effective aspect ratio of individual cells due to the motion of the flagella alone.     

Effects of temperature on growth,morphology, and photosynthesis in wheat

Several morphological characteristics differed when wheat (Triticum aestivum L. cv. Doha 88) was grown under a cool (10 °C), warm (20 °C), and hot (30 °C) regime. Development of leaves was linearly related to shoot meristem temperature, and the time between appearance of successive leaves on the main culm was independent of growth temperature. Area and dry mass of leaves and roots increased exponentially with time, and variations between growth temperature regimes were reduced when plants were compared at a similar developmental age. In isolated thylakoids thermal stability of photosystem 2 and of whole electron transport chain was enhanced with the increase in growth temperature. Therefore this cultivar is able to acclimate to contrasting temperature regimes.     

Oxygen dependence of photoinhibition at low temperature in intact protoplasts of Valerianella locusta L.

Photoinhibition of photosynthesis in vivo is shown to be considerably promoted by O₂ under circumstances where energy turnover by photorespiration and photosynthetic carbon metabolism are low. Intact protoplasts of Valerianella locusta L. were photoinhibited by 30 min irradiation with 3000 mol photons · m^–2 · s^–1 at 4° C in saturating [CO₂] at different oxygen concentrations, corresponding to 2–40% O₂ in air. The photoinhibition of light-limited CO₂-dependent photosynthetic O₂ evolution increased with increasing oxygen concentration. The uncoupled photochemical activity of photosystem II, measured in the presence of the electron acceptor 1,4-benzoquinone, and maximum variable fluorescence, F_v, were strongly affected and this inhibition was closely correlated to the O₂ concentration. The effect of O₂ did not saturate at the highest concentrations applied. An increase in photoinhibitory fluorescence quenching with [O₂], although less pronounced than in protoplasts, was also observed with intact leaves irradiated at 4° C in air. Initial fluorescence, F_o, was slightly (about 10%) increased by the inhibitory treatments but not influenced by [O₂]. A long-term cold acclimation of the plants did not substantially alter the O₂-sensitivity of the protoplasts under the high-light treatment. From these experiments we conclude that oxygen is involved in the photoinactivation of photosystem II by excess light in vivo.Abbreviations and Symbols Chl chlorophyll - F_o initial fluorescence - F_M maximum fluorescence - F_v maximum variable fluorescence - PCO photorespiratory carbon oxidation - PCR photosynthetic carbon reduction - PFD photon flux density - q_N non-photochemical quenching - q_P photochemical quenching - _S quantum efficiency of electron transport of photosystem II This study was financially supported by the Deutsche Forschungs-gemeinschaft (SFB 189) and the Foundation for Fundamental Biological Research (BION), which is subsidised by the Netherlands Organization for the Advancement of Pure Research (NWO).     

Effects of pressure on cell morphology and cell division of lactic acid bacteria

The effect of pressure and temperature on the growth of the mesophilic lactic acid bacteria Lactococcus lactis and Lactobacillus sanfranciscensis was studied. Both strains were piezosensitive. Lb. sanfranciscensis failed to grow at 50 MPa and the growth rate of Lc. lactis at 50 MPa was less than 30% of that at atmospheric pressure. An increase of growth temperature did not improve the piezotolerance of either organism. During growth under high-pressure conditions, the cell morphology was changed, and the cells were elongated as cell division was inhibited. At atmospheric pressure, temperatures above the optimal temperature for growth caused a similar effect on cell morphology and cell division in both bacteria as that observed under high-pressure conditions. The segregation and condensation of chromosomal DNA were observed by DAPI staining and occurred normally at high-pressure conditions independent of changes in cell morphology. Immunofluorescence microscopy of Lc. lactis cells demonstrated an inhibitory effect of high pressure on the formation of the FtsZ ring and this inhibition of the FtsZ ring formation is suggested to contribute to the altered cell morphology and growth inhibition induced by high pressure.Communicated by K. Horikoshi     

Effects of low temperature on lateral diffusion in plasma membranes on maize (Zea mays L.) root cortex protoplasts: relevance to chilling sensitivity

The effects of temperature on the lateral diffusion of fluorescent phospholipids, sterols and proteins in the plasma membranes of maize root cortex protoplasts were monitored using fluorescence photobleaching recovery (FPR). Diffusion parameters were measured in two cultivars of maize having different chilling tolerance. Hydrodynamic theory predicts that the diffusion coefficient, D, should increase with increasing temperature. In the more chilling-tolerant cultivar, however, D for all three probes was nearly insensitive to temperature. In the more chilling-sensitive cultivar, D was also insensitive to temperature over the range from 12 to 21°C, but D for the lipid probes tended to be higher and more variable at lower temperatures. The proportion of probe molecules free to diffuse in the membrane was less than 1 for all probes, and increased significantly with increasing temperature for the protein probe. These results, taken together, support the concept that the plasma membrane contains domains having differing diffusional characteristics. Temperature effects on membrane diffusion are moderated by the existence of these domains to limit significant changes. The observed tendency for higher diffusion coefficients at low temperatures in the chilling-sensitive cultivar may correlate to morphological changes observed with protoplasts of that cultivar at low temperatures.     

Effects of low temperature on induction and differentiation of wheat calluses

Young inflorescences and long-term culture calluses of wheat (Triticum aestivum L.) were used to investigate the effect of low temperature treatment on the potential of plant regeneration. The results indicated that the frequency of callus induction from immature inflorescences was decreased when treated for a long time at 5 °C. However, it was found that a 5 °C treatment significantly improved the regeneration frequency of calluses. The clear difference of peroxidases of wheat calluses was apparent after the cultures were treated at the low temperature. The isozyme band 8 became clearly faint, however, bands 6 and 9 became intense. This revised version was published online in June 2006 with corrections to the Cover Date.     

低温打蜡对贮藏菠萝黑心病控制的作用

研究了常温、低温、低温加打蜡 3种贮藏条件下菠萝果实硬度、可溶性固形物 (TSS)、可溶性糖醛酸、多聚半乳糖醛酸酶 (PG)和多酚氧化酶 (PPO)等因素的变化 ,及它们对黑心病发生及发展情况的影响。结果表明 ,低温加打蜡可以延缓果肉硬度、可溶性固形物和可溶性糖醛酸含量的下降 ,降低 PG和 PPO的活性 ,降低黑心病的发病率 ,较好的保持果实品质     

西方蜜蜂幼虫发育温度对成体翅膀形态的影响

为探讨不同恒定温度条件对培育蜜蜂蛹翅膀形态特征的影响,作者将进入蛹期的西方蜜蜂(Apismellifera)放入人工气候箱里,分别在32、35和36℃的恒定温度条件培育,直到蜜蜂蛹羽化出房为止。测量了蜜蜂翅膀的标准形态特征,包括翅的大小、肘脉长和11个翅肘脉角,所得到的数据进行多变量比较分析、相关性分析、主成分分析和区别分析。研究结果表明,不同温度条件对蜜蜂翅膀形态特征有明显的影响     

高山植物花形态特征对花温度积累的影响

高山生态系统的低温环境不利于植物繁殖器官的发育和传粉过程,因此能改善花内或花序温度的结构对植物繁殖具有积极意义。该研究利用红外测温仪测量了高寒草甸中64种植物的花温度和叶温度以计算花温度积累,并检测了系统发育、花大小、花对称方式和花大小对花温度积累的影响。结果表明:所测量的64种植物种类,花部温度均高于叶部温度。花温度积累的系统发育信号较弱,表明物种间花温度积累的差异可能主要与不同物种对温度的需求有关。花温度积累与花大小存在显著的正相关关系,且两侧对称花的温度积累比辐射对称花更为迅速,但花对称方式和花颜色对花温度积累并没有显著的影响。该研究结果表明花温度积累在不同植物间存在很大的差异,但这些差异对植物繁殖的实际贡献和意义仍需要进一步验证。     

Effects of quinacrine on endothelial cell morphology and transcription factor-DNA interactions

Quinacrine has been used for decades and the beneficial effects of this drug are as numerous as its toxic effects. Since endothelial cells (EC) are in many cases the first cells coming in contact with drugs, the effect of quinacrine on certain aspects of EC biology were studied. The presented data demonstrate that quinacrine can have a marked impact on the integrity on EC monolayer without grossly interfering with cell viability. The described impact of quinacrine on EC might explain, at least in part, the toxic effects of this drug observed in the past. Furthermore, quinacrine profoundly effects gene regulation in EC. Quinacrine binds to DNA in a sequence-specific manner. While NF-kappa B-DNA interactions are not effected, AP-1-DNA binding is blocked by quinacrine. Such differential effects are presumably due to intercalation of quinacrine into the AP-1 consensus element. Preincubation of oligonucleotides resembling this sequence blocked the subsequent binding of nuclear extract containing AP-1 protein(s). Taken together, these data suggest that quinacrine interferes with EC physiology and alters the repertoire of EC to respond to stimuli. Furthermore, the differential effects of quinacrine might be exploited to study and gain additional insight in the involvement of AP-1 and NF-kappa B in gene regulation.     

Effect of fusicoccin on plant cell cultures and protoplasts

We have assayed the capacity of the fungal toxin fusicoccin to induce some of its characteristic effects (acidification of the medium, stimulation of K⁺, and of 3-O-methyl-D-glucose uptake) in cell suspensions of Parthenocissus tricuspidata (Siebold et Zucc.) Planchon, Acer pseudoplatanus L. and Oryza sativa L., and in protoplast suspensions prepared from leaves of Nicotiana tabacum L. and Spinacia oleracea L. or from cultures of P. tricuspidata. Evidence is presented showing that all tested biological materials respond to the addition of fusicoccin. The observation that the toxin is also active on protoplasts indicates that the cell wall is not involved in the mechanism of action of fusicoccin.Abbreviations FC Fusicoccin - 3-O-MG 3-O-Methyl-D-glucose     

低温胁迫对番茄种子萌发的影响

在人工气候箱中模拟3个低温处理(24h最低/最高温度分别设定为7℃/12℃、5℃/10℃和3℃/8℃),分析了播种后不同天数低温胁迫对番茄种子萌发的影响。结果表明:与对照(18℃/25℃)相比,低温胁迫处理的温度越低影响越大,当日最低温度达到5.0℃、日均温低于10.0℃(相当于低温胁迫处理7℃/12℃)时,对番茄种子萌发的影响较为严重;播种后越早经受低温影响越大,播种后3d内经受低温胁迫,番茄种子发芽势、发芽指数和萌发率均有较大的下降,播种6d后低温胁迫对其萌发指标的影响较小;低温胁迫影响种子萌发的原因主要是低温导致了α-淀粉酶活性下降,相对离子渗漏率增加,从而减缓了番茄种子贮藏物质的降解,影响了番茄种子萌发初期的物质与能量代谢,并增强了细胞膜的透性,导致外渗物增多。