Uptake of glycollate by Skeletonema costatum (Grev.) Cleve in bacterized culture

Glycollic acid, supplied at a concentration of 1 mg l^?1, increased the relative growth rate of Skeletonema costatum (Grev.) Cleve growing in bacterized culture at limiting light intensities. There was little or no such effect at intensities approaching saturation. The presence in the medium of alumina, an adsorbent for glycollate, prolonged the lag phase, the cells remaining viable for up to 5 days. Uptake of glycollate was not appreciably affected by the bicarbonate concentration of the medium. After 3 h, 80–92% of the glycollate carbon assimilated was found in the alcohol and benzene insoluble fraction of the cells. This is in agreement with the supposition that glycollate carbon is as-similated directly by the diatom rather than after degradation by bacteria to carbon dioxide.     

Alkaline and acid phosphatases of the marine diatoms Chaetoceros affinis var. willei (Gran) Hustedt and Skeletonema costatum (Grev.) Cleve

Alkaline phosphatase activity in cultures of the marine diatom Chaetoceros affinis var. willei (Gran) Hustedt was higher than in Skeletonema costatum (Grev.) Cleve. The enzyme activity was localized in coarse cell particles. Acid phosphatase activity was found in the cytoplasmic fraction. Induction of alkaline phosphatase depended on the $\text{N}\text{P}$ ratio in the culture medium. A $\text{N}\text{P}$ ratio > 40 in dilution/batch culture and > 30 in large scale batch culture, respectively, induced alkaline phosphatase.Cell phosphorus showed a critical value below which alkaline phosphatase was induced. Alkaline phosphatase in natural phytoplankton from the Trondheimsfjord is unlikely to occur except possibly in special situations.     

The adenylate energy charge in marine phytoplantkon: The effect of temperature on the physiological state of Skeletonema costatum (Grev.) Cleve

The adenylate energy charge $\text{([ATP] +}\text{1}\text{2}\text{[ADP])}\text{[0ATP+ADP+AMP]}$ was measured in axenic batch cultures of Skeletonema costatum (Grev.) Cleve at 2°, 10°, 15°, 20°, 24° and 30°C. The results suggest that this eurythermal diatom is physiologically capable of adapting to the 28 °C range of temperature with little apparent difference in the potential energy available to the cell. In N-limited continuous cultures at 15 °C, the energy charge values were lower than those observed in batch culture by 0.2, implying nutrient stress may result in decreased intracellular chemical energy. The utilization of the adenylate energy charge as an indicator of physiological state is suggested.     

Dynamics in the size structure of Skeletonema costatum (Greville) Cleve under conditions of reduced photosynthetically available radiation in a dredged tropical estuary

This study investigates the size-fractionated productivity and chlorophyll a concentrations in Ponggol estuary, a heavily dredged, light-limited and eutrophic tropical estuary located on the northeastern coast of Singapore. A 90% reduction in the photosynthetically available radiation (PAR) was seen in the subsurface waters of the dredged stations, when compared to an average reduction of about 75% in the subsurface waters of the un-dredged station. High phytoplankton production rates and chlorophyll a concentrations were recorded in the surface waters, with a significant reduction in the subsurface waters, especially at the two dredged stations. Out of the four size-classes of phytoplankton (0.2-2 μm, 2-20 μm, 20-200 μm and >200 μm) investigated, the relative dominance of the smaller size class of 2-20 μm over the 20-200 μm size class shifted depending on the availability of PAR. The size class 2-20 μm was observed to contribute up to 60 and 57% of the total production, respectively, in the surface waters of the un-dredged and dredged stations of the estuary. A relatively major contribution of 49% came from the cells of the small size-fraction of 2-20 μm in the subsurface waters of the un-dredged station. On the contrary, cells of the 20-200 μm size-class contributed up to 58% in the subsurface waters of the dredged station. Microscopic examination of the phytoplankton cells sampled showed morphological differences in the cells of the phytoplankton species Skeletonema costatum with some cells being distinctly larger in size than others. The larger cells were predominant in the dredged subsurface waters. In situ mesocosms with treatments exposed to high light irradiation registered a significant contribution by the smaller size-class of 2-20 μm, in contrast to the larger 20-200 μm dominating in the two treatments subjected to low light conditions. Based on the observations in this study and a review of the literature, it is hypothesized that the cells of S. costatum may actually be of two genetically different strains, whose relative dominance in the environment may be controlled by the quantum of available light. Thus, this shift in the relative dominance of one size fraction over the other is a response to altered PAR levels as the result of dredging.     

Ultraviolet radiation negatively affects growth and food quality of the pelagic diatom Skeletonema costatum

There are now compelling observations of the ecological impacts of global change on marine ecosystems. A predicted 10% increase in UVB doses at the Earth's surface has been shown to impair indirectly the reproductive output of marine copepods. Wild females of Calanus helgolandicus fed with UVB-irradiated diatoms produced fewer eggs and unhealthy offspring exhibiting a large proportion of high lethal naupliar deformities. By reproducing the same irradiative stress on the pelagic diatom Skeletonema costatum, we looked for potential modifications of the algal properties (cell size, biovolume, chlorophyll content) and biochemical characteristics (fatty acid and amino acid contents). Our results confirmed that the metabolism of S. costatum is adversely affected by enhanced UVB exposure: cell growth was reduced and the biochemical characteristics, and thus the algal nutritional quality, were significantly altered. UVB irradiation reduced cell division, leading to cell elongation and thus increasing the biovolume. Meanwhile, the amino acid and fatty acid contents did not increase concomitantly to the cell enlargement and were thus diluted in the cell. Because of this dilution, the irradiated S. costatum represents a poorer diet for its potential consumers. Moreover, UVB dramatically affects the relative contribution of certain essential fatty acids such as eicosapentanoic acid (EPA), which are essential for the development of marine invertebrates.     

浒苔干粉末提取物对东海原甲藻和中肋骨条藻的克生作用

研究不同溶剂的浒苔干粉末组织提取液对两种赤潮藻—东海原甲藻和中肋骨条藻生长的克生效应。结果表明, 浒苔提取物中确实含有可以影响赤潮藻类生长的克生物质,克生作用具有较明显的浓度效应,添加浓度低时可能会表现为一定的促进生长的作用,添加浓度较高时表现为抑制作用,添加浓度越大,抑制作用越强,即“低促高抑”的特点,这与浒苔提取物对其他微藻的作用相似。其中,蒸馏水提取物对这两种赤潮藻的克生作用小于有机溶剂提取物,有机溶剂中,甲醇和乙酸乙酯提取物对这两种赤潮藻的克生效果最好,正己烷相对较差。根据相似相溶原理,可以初步推断最有效的克生物质应为具有相对较高的极性的有机物。两种赤潮藻对克生物质的敏感程度不同。东海原甲藻对克生物质的敏感性高于中肋骨条藻。蒸馏水、甲醇、乙酸乙酯、正己烷的浒苔干粉末提取物影响东海原甲藻生长的致死作用阈值浓度分别为5.00 g/L、0.50 g/L、0.50 g/L、0.63 g/L（相当于浒苔新鲜藻体浓度为22.00 g-wet/L、2.20 g-wet/L、2.20 g-wet/L、2.75 g-wet/L）;影响中肋骨条藻生长的致死作用阈值浓度则分别为20.00 g/L、1.25 g/L、1.25 g/L、2.50 g/L（相当于新鲜藻体浓度为88.00 g-wet/L、5.50 g-wet/L、5.50 g-wet/L、11.00 g-wet/L）。     

Examination of the type materials ofNavicula subtilissima Cleve (Bacillariophyceae)

Navicula subtilissima was described by Cleve as a new species from ‘a dry rivulet at the shore of Imandra, at the foot of Chibinä, Lapland’. However, the examination of the type slides and the unmounted original material using transmission and scanning electron microscopy revealed that there are at least three finely striated similar taxa distinguishable at the specific level. From these taxa, application of the nameN. subtilissima Cleve is established by selecting a lectotype; a second one is described as a new species,N. parasubtilissima, and the third is identified asN. subtilissima var.micropunctata Germain. The last one warrants a specific status by its fine structural differences in having continuous striae consisting of a single elongate areola occluded by a hymen with perforations arranging hexagonally. The occurrence of these three species is shown in Japanese collections.     

Effects of light intensity on the growth and diurnal variation of photosynthesis in Evod iarutaecarpa seedlings

报道了不同生长光强(透光率分别为15％、30％、50％、100％)对吴茱萸的生长和光合日变化的影响.结果表明:生长环境光强对吴茱萸苗期株高、地径和冠面积的影响较大,100％ RI下的株高、地径和冠面积明显小于各遮荫处理,其中30％ RI下吴茱萸的株高、地径和冠面积最大,这表明苗期强光不利于吴茱萸的生长.随着光强的减弱,吴茱萸增大冠面积与株高有利于截获更多光能.10月下旬,100％ RI下吴茱萸净光合速率(Pn)日变化曲线呈“双峰型”,11:30～14:30,吴茱萸的Pn、胞间二氧化碳浓度与气孔导度均下降,表明此时的光合午休现象是由气孔部分关闭造成的.各遮荫处理下,吴茱萸的Pn日变化均呈“单峰型”,并无第二峰的出现,可能与遮荫条件下,下午光强较弱,环境温度较高,空气相对湿度较低有关.     

Observations on Cymbella mexicana (Ehrenb.) Cleve var. mexicana (Bacillariophyceae) with special reference to the band structure

Cymbella mexicana (Ehrenb.) Cleve var. mexicana was collected from Tama-gawa (Tama River), Tokyo. The fine structure of the species was examined by scanning electron microscopy (SEM), with special reference to colony formation and band morphology. A mature cingulum of this species is usually composed of four open bands. The correlation between the position of the second band (B2) of the cingulum and the attaching pole of the frustule is discussed.     

Effects of light intensity on membrane differentiation in Rhodopseudomonas capsulata

Cells of Rhodopseudomonas capsulata, strain 37b4, leu^?, precultivated anaerobically under low light intensity, were exposed to high light intensity (2000 W · m^?2). The cells grew with a mass doubling time of 3 h. The synthesis of bacteriochlorophyll (BChl) began after two doublings of cell mass. Reaction center and light-harvesting BChl I (B-875) were the main constituents of the photosynthetic apparatus incorporated into the membrane. The size of the photosynthetic unit (total BChl/reaction center) decreased and light-harvesting BChl I became the dominating BChl species. Concomitant with the appearance of the different spectral forms of BChl the respective proteins were incorporated into the membrane, i.e. the three reaction center polypeptides, the polypeptide associated with light-harvesting BChl I, the two polypeptides associated with BChl II. A polypeptide of an apparent molecular weight of 45 000 was also incorporated. A lowering of the light intensity to 7 W · m^?2 resulted in a lag phase of growth for 6 h. Afterwards, the time for doubling of cell mass was 11 h. The concentration of all three BChl complexes (reaction center, light-harvesting BChl I and II complexes)/cell and per membrane protein increased immediately. Also the size of the photosynthetic unit and the amount of intracytoplasmic membranes/cell increased.The activities of photophosphorylation, succinate dehydrogenase, NADH dehydrogenase and NADH oxidation (respiratory chain)/membrane protein are higher in membrane preparations isolated from cells grown at high light intensities than in such preparations from cells grown at low light intensities.     

Copper toxicity and copper tolerance in Enteromorphacompressa (L.) Grev.

The responses of ship-fouling and non-fouling isolates of Enteromorpha compressa (L.) Grev. have been compared in media containing copper at 0.0?9.6 μmol · dm^?3. The responses of each isolate were found to vary, according to the conditions of the original habitat. Thus ship-fouling E. compressa was found to be tolerant of copper concentrations up to 9.6 μmol · dm^?3 showing a maintenance of all of the physiological processes studied during the present research (cell viability, net photosynthesis, intracellular K⁺ and dimethylsulphoniopropionate content). Non-fouling plant material showed symptoms of copper toxicity at all levels of copper from 1.8 μmol · dm^?3 to 9.6 μmol · dm^?3. Copper tolerance in ship-fouling E. compressa appears to be genetically determined, since the progeny from ship-fouling plants are also tolerant to copper concentrations within the range 1.8 to 9.6 μmol · dm^?3. The rate of accumulation of copper in ship-fouling thalli is, however, almost identical to that of non-fouling thalli, suggesting that tolerance may be due primarily to internal detoxification, rather than an exclusion mechanism.     

Photosynthetic rapid light curves (RLC) of Thalassia testudinum exhibit diurnal variation

The use of pulse-amplitude-modulated fluorometry (PAM) and rapid light curves (RLC) were evaluated for monitoring the physiological condition of the seagrass, Thalassia testudinum, at the landscape scale in Florida Bay, USA. PAM fluorometry provides rapid, non-invasive, and quantitative physiological information on the state of photosynthesis. Yet, previous studies of effective and maximum quantum yields have shown that problems arise when expanding measurements from the organismal scale to the landscape scale, mainly due to temporal and irradiance-induced changes in photophysiology. Here, the magnitude of diurnal and spatial variation of photosynthetic characteristics among 10 sample basins and between two sample years was investigated using RLCs. Because RLCs measure effective quantum yields over a range of changing actinic irradiances, we hypothesized that the response parameters might be less sensitive to diurnal light history effects. Our results indicate that the RLC parameters, alpha and ETR_max, significantly changed diurnally, as was previously found for both maximum and effective quantum yields, but the diurnal patterns were variable among the 10 basins. Both among-basin and between-year comparisons were confounded by diurnal variation and statistical analyses comparing morning, mid-day, and afternoon time periods were unable to definitively discern which time of day was best suited for assessing the relative photophysiological status of T. testudinum. However, pooling RLC data at the basin scale revealed among-basin differences and landscape scale trends that were consistent with basin-level morphometric variation in this seagrass. Thus, PAM fluorometry may be useful as a landscape scale monitoring tool within certain constraints. When using this approach over large spatial and temporal scales, diurnal variability must be considered.     

Effects of light intensity and nutrients on gametophytes and gametogenesis of Lessonia nigrescens Bory (Phaeophyta)

Meiospores of Lessonia nigrescens Bory collected in Central Chile, were cultivated under different light and nutrient conditions to test for their influence on the development of gametophytes and gametogenesis. The microscopic stages of the life cycle are described. Under 45 μE·m^?2 ·s^?1 (12 h daily) and sea water enriched with nitrate and phosphate, development of few-celled gametophytes, gametogenesis and sporophyte differentiation occur within 35 days. At 10 μE ·m^?2 · s^?1, most gametophytes are multicellular and remain vegetative up to 65 days. Only enriched sea water or enriched sea water with double concentrations of phosphate lead to fertile few-celled gametophytes under 45 μE · m^?2 · s^?1. The addition of double concentrations of nitrate allows for the development of few-celled gametophytes but inhibits gametogenesis. The average gametophyte size progressively decreases when increasing amounts of nitrate and phosphate are added to the media.     

光照强度和肥力变化对垂穗披碱草生长的影响

在野外条件下,采用析因设计,对光照和肥力变化影响下垂穗披碱草的生长参数进行测定,评估垂穗披碱草对异质环境的适应特性。光照分为高光照(100%光照强度)、中度光照(43.5%光照强度)与低光照(6.74%光照强度);肥力分为施肥与不施肥。结果表明,垂穗披碱草在光照强度由高光照(100%)向中度光照(43.5%)变化情况下,地上生物量、分蘖数无变化,株高增大,光照强度减小到6.74%时,地上生物量、分蘖数、株高均减小。比叶面积(SLA)随光照强度的减弱而增加,相对生长率(RGR)随光照强度的减弱而减小,施肥对SLA和RGR无影响。根冠比在中度光照和低光照下各处理之间差异均不显著,高光照(100%)下增加肥力,根冠比增大。施肥时,叶分配随光照强度的减弱而增加,繁殖分配减小,不施肥时,叶分配与繁殖分配在高光照(100%)和中度光照(43.5%)下无差异,低光照(6.74%)下,叶分配增大,繁殖分配减小。施肥时茎分配在中度光照强度(43.5%)下最大,高光照强度(100%)下次之,低光照强度(6.74%)下最小,不施肥时,茎分配在高光照(100%)和中度光照(43.5%)下无差异,低光照(6.74%)下减小。研究表明:垂穗披碱草是一个光照耐受型物种,光照强度减小到全光照一半时仍可正常生长。在低光环境中,垂穗披碱草通过增加株高和大而薄的叶片,来适应环境,资源主要在叶分配、茎分配、繁殖分配之间进行了权衡。     

不同光照强度对小球藻生长的影响

【目的】优化小球藻的培养与提高资源化利用效率,得到不同光照强度对小球藻生长的影响规律。【方法】通过室内控制实验,设置0、1 000、3 000、5 500、7 000、9 000 lx共6组光照强度,在温度为20°C和曝气强度为20%的条件下,采用BG-11培养基培养小球藻(Chorella vulgaris)至稳定生长,研究不同光照强度对小球藻生长的影响,建立光照强度与最大光密度ODmax、最大比增长率μmax之间的抛物回归曲线。【结果】不同光照强度下,小球藻生长差异较大,培养初期叶绿素a浓度迅速增加直至峰值,后期迅速降低,其中5 500 lx强度下小球藻生长最好。藻类生长对溶解性总磷的消耗比溶解性总氮更大。【结论】光照强度(x)与ODmax的拟合方程为:ODmax=-1E–07x~2+0.001 6x+0.105 5(R~2=0.987 2,0≤x≤9 000 lx),光照强度(x)与μmax的拟合方程为:μmax=-2E–08x~2+0.000 3x-0.004 2(R~2=0.998 6,0≤x≤9 000 lx)。     

Physiology of diatom Skeletonema costatum (Grev.) Cleve photosynthetic extracellular release: evidence for a novel coupling between marine bacteria and phytoplankton

The photosynthesis of cellular materials by phytoplankton isaccompanied by release of organic molecules from the algal cellsinto the water. The patterns of carbon fixation in particulateand dissolved pools were investigated in Skeletonema costatumcultured under 12 h light/12 h dark cycles. The short-term production(1–15 min) of particulate organic carbon (POC) and extracellularorganic carbon (EOC) compounds was studied by measuring theuptake of ¹⁴C-labelled sodium bicarbonate and its subsequentincorporation and release into organic compounds. Slightly modifiedtraditional ¹⁴C radiotracer protocols were used, including separationby electrophoresis and thin-layer chromatography and detectionby autoradiography. Results indicated that there was a distinctdifference between radiolabelled compounds in the POC and EOCpools. Several metabolites found in the EOC pool were not presentin the POC pool, indicating the active release of these productsfrom the cells into the ambient water during short-term incubations,and indicating that inorganic carbon fixation pathways in marineautotrophs might be partly extracellular.     

Effects of light intensity and nitrogen level and source on growth of corn (Zea mays L.) in a controlled environment

Summary The growth response of corn (Zea mays L.) to two light intensities and two levels of nitrogen from ammonium and nitrate sources in nutrient solution was studied in a growth chamber under controlled humidity, photoperiod and temperatures. Light intensity and NO₃-N increased the first 4-week vegetative growth of leaf, stalk and root, resulting in each case in a positive significant light intensity × NO₃-N interaction. While light intensity enhanced the vegetative growth of the NH₄-treated plants, NH₄-N itself had no effect. No interaction was noted. Part of a Ph. D. thesis submitted by the Senior Author in 1969 to the Graduate Faculty of Studies and Research, McGill University. Former graduate assistant and associate professor respectively.     

The influence of light intensity on the roosting times of the rook (Corvus frugilegus)

Little work has been done on the roosting behaviour of Corvidae, particularly the influence of light-intensity on its timing. This paper describes the effects of light-intensity on the roosting times of rooks (Corvus frugilegus) from a large roost during winter. Light intensity was measured and its influence on the departure of birds from the feeding grounds, arrival at the roost, entry into the roost and morning departure was found to be significant. Departure from feeding areas (and arrival at the roost) was earlier at lower light-intensities and later at higher light-intensities. Control of responsiveness to light-intensity by circadian rhythm for rooks from different feeding grounds was discussed.     

Effects of light intensity on the growth and buoyancy of detachedElodea nuttallii (Planch.) St. John during winter

The influences of light intensity on the growth and buoyancy of detachedElodea muttallii (Planch.) St. John during winter were examined under controlled experimental light conditions. Light was controlled by mesh-screens at five levels ranging between 0.3 and 51% of the aerial full sunlight in an outdoor pond. Growth of detached segments was compared with respect to shoot and root lengths, dry weight and starch content in tissues. Buoyancy of segments at each light level was evaluated by percentage frequency of floating segments. Critical light intensity for the winter growth was estimated as ca. 4.5% of the aerial full sunlight. Most segments at light levels lower than 4.5% had been floating in water since the early period of the experiment, while all segments at light levels higher than 17% had been sinking to the bottom until water temperature became higher than 10 C. The data on segment buoyancy and tissue analysis for starch content showed an inverse relationship between percentage frequency of floating segments and starch content in tissues. These results suggest that detached segments in nature could escape from the photosynthetically unsuitable regions by reduced specific gravity caused by the consumption of starch, and establish themselves only if they could arrive at a safe-site where light conditions are sufficient to accumulate photosynthate.