The fine structure of Synura sphagnicola (Korsh.) Korsh. (Chrysophyceae)

S. sphagnicola resembles other species of Synura previously described by electron microscopy in most features of structure but differs in possessing pyrenoids and up to five cylindrical stacks of smooth cisternae which occur between the pyrenoids and leucosin vesicles. Each stack is surrounded by a tubular cisterna which bears ribosomes on its distal face but there are no clear permanent connections between this and the chloroplast ER. Other features apparently unique to this species previously known from light microscopy are described. These include the axial position of the chloroplasts; the peripheral position of the leucosin vesicles; and the loose attachment of the scales. The structure of the body scales is described for the first time from sections. The flagellar scales are formed in the swollen edges of the Golgi cisternae and appear to pass to the cell surface in large vesicles.     

Ecophysiological studies on Spirulina platensis Effect of temperature,light intensity and nitrate concentration on growth and ultrastructure

The ultrastructure of the cyanobacterium Spirulina platensis was studied in relation to temperature, light intensity and nitrate concentration. The organism was able to grow in media supplied with nitrate in concentrations up to 250mm. High nitrate concentrations increased the yield and growth rate at temperatures above 35°C. Occurrence, distribution and abundance of cyanophycin granules, polyglucan granules, cylindrical bodies, carboxysomes and mesosomes varied widely in relation to the factors studied. At low temperatures (up to 17°C) cyanophycin was the abundant organelle, especially at high nitrate concentrations, whereas in the temperature range 17–20°C polyglucan was found in large quantities particularly at low nitrate concentrations. Special attention was paid to the cylindrical bodies, the ultrastructure of which was dependent on temperature. Three types of ultrastructure were distinguished each with several possible shapes.     

Effect of temperature,light intensity and dilution rate on the cellular composition of red algaPorphyridium cruentum in light-limited chemostat cultures

Summary The fatty acid, polysaccharide and pigment contents ofPorphyridium cruentum at different growth temperatures, light intensities and dilution rates were studied in light-limited chemostat. The highest biomass yield was obtained at 25°C over the range of dilution rate studied (0.079 to 0.30 day^–1). The production of fatty acids increased with increasing dilution rates. At low dilution rates, the contents of fatty acids at 20°C, 25°C and 30°C were comparable. Temperature did not affect the content of linolenic acid (182) though fatty acids with less than two double bonds predominated at higher temperatures, those with more than two double bonds accumulated at lower temperatures. The yields of arachidonic acid (204) increased under light of higher intensity. The maximum production of extracellular and cellular polysaccharides occured at low dilution rates under high light at 25°C. The amounts of chlorophylla, carotenoids and phycoerythrin all increased in the same proportions with dilution rate, and were highest at 25°C.

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Resumen Se estudió el contenido en polisaccaridos, pigmentos y ácidos grasos dePorphyridium cruentum a distintas temperaturas, intensidades lumínicas y porcentajes de dilución en un quimiostato con luz limitada. La mayor cantidad de biomasa para todas las diluciones estudiadas (0.079 a 0.30 día^–1) se obtuvo a 25°C. A bajas diluciones los contenidos en ácidos grasos a 20°C, 25°C y 30°C eran comparables. La temperatura no afectó al contenido en ácido linolénico (182), sin embargo los ácidos grasos con menos de dos dobles enlaces se acumularon a temperaturas más bajas. La producción de ácido arachidónico (204) se incrementó bajo la mayor intensidad lumínica ensayada. La producción máxima de polisaccaridos celulares y extracelulares se dió a bajas diluciones en condiciones de alta iluminación a 25°C. Las cantidades de clorofila a, carotenoides y ficoeritrina se incrementaron paralelamente al porcentaje de dilución siendo más elevadas a 25°C.

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Résumé On a étudié le contenu dePorphyridium cruentum en acides gras, en polysaccharides et en pigments, en fonction de la température de croissance, de l'intensité lumineuse et du taux de dilution dans un chémostat limité par la lumière. Le rendement le plus élevé en biomasse a été obtenu à 25°C quel que soit le taux de dilution (compris entre 0.079 et 0.30 jours^–1). La production d'acides gras augmente avec l'augmentation du taux de dilution. A des taux de dilution faibles, le contenu en acides gras est indépendant de la température (comprise entre 20 et 30°C). La température n'influence pas le contenu en acide linolénique (182) bien que les acides gras à deux ou plusieurs doubles liaisons s'accumulent à température plus basse. Les rendements en acide arachidonique (204) augmentent sous une lumière de plus forte intensité. La production maximum de polysaccharides tant extracellulaires que cellulaires a lieu à un taux faible de dilution sous une lumière intense à 25°C. Les teneurs en chlorophylle a, caroténoïdes et en phycoerythrine augmentent toutes les trois dans les mêmes proportions avec le taux de dilution et sont les plus élevées à 25°C.

     

温度升高对高光强环境下蛋白核小球藻(Chlolorella pyrenoidosa)光能利用和生长的阻抑效应

以蛋白核小球藻（Cholorella pyrenoidosa）为实验材料,研究了温度变化对不同光照水平下蛋白核小球藻的光能利用和生长的影响,以明确光照强度对微藻的光能利用和生长的影响是否因温度不同而发生变化。实验中共设置了3个光照强度水平（50,150,300μmol·m^-2s^-1）和2个温度水平（15℃,25℃）。实验结果表明,不同光照水平下小球藻叶绿素荧光的非光化学淬灭（NPQ）大小与温度有关,光照强度为150,300μmol·m^-2s^-1时,温度升高使小球藻叶绿素荧光NPQ提高,并且光照强度越高小球藻叶绿素荧光NPQ增大越多,50μmol·m^-2s^-1光照强度下温度升高对叶绿素荧光NPQ没有影响。实验发现,25℃培养温度下小球藻的光合电子传递速率（ETR）随光照强度增高而上升的速率要低于15℃时小球藻ETR上升的速率;随着光照强度增高,温度升高使小球藻ETR降低程度增大。实验结果还表明,15℃时小球藻培养液叶绿素a浓度随光照强度升高而增高,300μmol·m^-2s^-1培养光强下具有最高的叶绿素a浓度。但在25℃时,光照强度升高叶绿素a浓度并不一定增高,300μmol·m^-2s^-1光照强度下的叶绿素a浓度比150μmol·m^-2s^-1光照强度下要低。本研究表明,温度升高增大了高光照水平下蛋白核小球藻对光能的热耗散,使光照增强对小球藻生长的促进作用减弱。由于温度升高对小球藻光能利用和生长的阻抑作用,小球藻生长的适宜光照水平因温度升高而降低。     

光照对蔺草生长和草茎开花率的影响

蔺草草茎长度和是否开过花是决定其品质的两个重要方面。试验表明,不同光周期及光照强度对蔺草的生长和草茎开花率会产生显著影响。生育前期,延长日照显著促进开花,遮光处理降低蔺草的分蘖、草茎长度、减少草茎开花率和每花序小花数。中后期对蔺草进行一定遮光处理后,草茎长度增加,开花率下降。试验表明,光照是造成蔺草开花逆转和影响草茎品质的重要生态因子之一。     

Influence of the growth rate calculation on the relationship between growth rate and temperature

Three calculations of the growth rate (e.g. slope of a plot of the log10 of cfu ml-1 vs time, mum of the Gompertz equation and the reciprocal of time to obtain 108 cfu ml-1) were compared for Escherichia coli TG1 growing in tryptone soy broth medium at temperatures ranging from 14 to 39 degrees C. Up to now, the influence of using such different definitions on the relationship between microbial growth rate and temperature has never been investigated. In order to compare these calculation procedures, a dimensionless analysis based on the following normalized variables, mudim = mu/muopt and Tdim = [T-Tmin]/[Topt-Tmin], was used (Dantigny 1998). The influence of suboptimal temperatures on the growth rate was represented by means of a Belehràdek-type model based on a power function law: [mudim] = [Tdim]alpha. The influence of the different growth rate calculations on the model constants was assessed. Despite the great dependence of the raw growth rate values on the calculation procedure, the dimensionless analysis demonstrated that the alpha-value is independent of the growth rate definition. This result suggests that any definition for the growth rate can be utilized in studies aimed at determining the influence of temperature on microbial growth and highlights the interest of using dimensionless variables to overcome differences in the order of magnitude of the growth rate data and to avoid confusion between definitions.     

Effect of oxygen concentration on the growth of Nannochloropsis sp. at low light intensity

In large-scale microalgal production in tubular photobioreactors, the build-up of O(2) along the tubes is one of the major bottlenecks to obtain high productivities. Oxygen inhibits the growth, since it competes with carbon dioxide for the Rubisco enzyme involved in the CO(2) fixation to generate biomass. The effect of oxygen on growth of Nannochloropsis sp. was experimentally determined in a fully controlled flat-panel photobioreactor operated in turbidostat mode using an incident photon flux density of 100?μmol photons m(-2) s(-1) and with only the oxygen concentration as variable parameter. The dissolved oxygen concentration was varied from 20 to 250% air saturation. Results showed that there was no clear effect of oxygen concentration on specific growth rate (mean of 0.48?±?0.40?day(-1)) upon increasing the oxygen concentration from 20% to 75% air saturation. Upon further increasing the oxygen concentration, however, a linear decrease in specific growth rate was observed, ranging from 0.48?±?0.40?day(-1) at a dissolved oxygen concentration of 75% air saturation to 0.18?±?0.01?day(-1) at 250% air saturation. In vitro data on isolated Rubisco were used to predict the quantum yield at different oxygen concentrations in the medium. The predicted decrease in quantum yield matches well with the observed decrease that was measured in vivo. These results indicate that the effect of oxygen on growth of Nannochloropsis sp. at low light intensity is only due to competitive inhibition of the Rubisco enzyme. At these sub-saturating light conditions, the presence of high concentrations of oxygen in the medium induced slightly higher carotenoid content, but the increased levels of this protective antioxidant did not diminish the growth-inhibiting effects of oxygen on the Rubisco.     

Combined effect of temperature and light intensity on growth and extracellular polymeric substance production by the cyanobacterium Arthrospira platensis

The effects of light intensity and temperature on Arthrospira platensis growth and production of extracellular polymeric substances (EPS) in batch culture were evaluated using a three-level, full-factorial design and response surface methodology. Three levels were tested for each parameter (temperature: 30, 35, 40°C; light intensity: 50, 115, 180 μmol photons m⁻² s⁻¹). Both growth and EPS production are influenced mainly by the temperature factor but the interaction term temperature*light intensity also had a significant effect. In addition, conditions optimising EPS production are different from those optimising growth. The highest growth rate (0.414 ± 0.003 day⁻¹) was found at the lowest temperature (30°C) and highest light intensity (180 μmol photons m⁻² s⁻¹) tested, no optima were detectable within the given test range. Obviously, optima for growth must be at a temperature lower than 30°C and a light intensity higher than 180 μmol photons m⁻² s⁻¹. For EPS production, light intensity had a positive linear effect (optimum obviously higher than 180 μmol photons m⁻² s⁻¹), but for the temperature parameter a maximum effect was detectable at 35°C.     

Effect of blue-green light on growth rate and chemical composition of three diatoms

The diatomsChaetoceros sp.,Skeletonema costatum andThalassiosira pseudonana were grown with different irradiances of white and of blue-green light, and with a mixture of blue-green plus 6.5 mol m^–2 s^–1 of white light. Exponential growth rates were higher in mixed blue for the first two, whileT. pseudonana grew faster in white light but, in all cases, mean cell division rates did not differ with increasing irradiances. Harvesting in stationary, rather than in late exponential growth phase, resulted in higher protein contents forChaetoceros sp. andS. costatum, but forT. pseudonana the highest value was in the exponential phase. The highest protein content was in blue-green light for the three species and it increased with irradiance. As to other fractions, the three strains showed different responses, related to quality and quantity, as well as to culture ages.     

Effects of variation in temperature and light intensity at different times on growth and yield of spring wheat

Spring wheat grown in pots outdoors was transferred to growth rooms for various periods to study the effect of increasing the temperature from 14-4 to 20-3 ^oC (Expt 1) or from day/night values of 15-0/15-2 to 20-0/15-2 ^oC (Expt 2) and of increasing the amount of visible radiation in a 16 h day from 424 to 792 J cm^-2 (Expt 1) or 374 to 740 J cm^-2 (Expt 2). There were no interactions between temperature and radiation. In Expt 1 neither the increase in temperature nor extra radiation, applied for 14 days immediately after the appearance of double ridges on the stem apex, or 14 days later, increased grain yield at maturity. Warmth early, but not late, increased dry weight, leaf area and the number of floret primordia immediately after treatment, but these effects had disappeared by anthesis, 30 days later. Dry weight but not leaf area was increased by extra radiation but the effects had disappeared 2 wk after treatment. An increase in temperature imposed for 16 days starting 5 or 21 days after anthesis (Expt 2) increased dry weight of the ear and decreased that of the rest of the plant immediately after treatment, and decreased leaf area at all times. When plants from the two temperatures were put together in the same conditions, ear growth of plants that had been in the warm was slower than that of plants from the cold treatment, so that the difference in ear weight observed after 16 days of treatment reversed and grain yield was decreased by warmth applied in either period; the component of yield decreased by warmth was grain size. Additional radiation in either post-anthesis period increased dry weight of all parts of the plant and had negligible effects on leaf area. Final grain yield was increased by c. 15% because the individual grains were larger. Early treatment also increased grain number slightly. The effects of treatment during the two post-anthesis periods were similar in size, and additive.     

温、光、盐对三角褐指藻紫外诱变株生长、总脂及脂肪酸的影响

为了优化微藻培养条件,采用单因子试验研究了不同温度(10、15、20、25、30℃)、不同光照强度(20、40、60、80、100、120μmol·m-2·s-1)和不同盐度(5、10、15、20、25、30、35、40)对三角褐指藻紫外诱变株MP-2的影响。结果表明:温、光、盐对MP-2的生长、总脂含量和脂肪酸组成影响显著(P0.05)。MP-2生长和总脂积累的适宜温度为10~25℃,最适20℃;低温有利于EPA和PUFA的积累,15℃时EPA(30.94%)和PUFA(39.53%)较高;MP-2生长的适宜光照强度为20~120μmol·m-2·s-1,最适光强为40μmol·m-2·s-1,低光强有利总脂的积累,光照强度为20~40μmol·m-2·s-1时总脂含量(25.81%~25.26%)较高;光强对PUFA和EPA的积累影响显著(P0.05),光照强度100μmol·m-2·s-1时EPA高达29.15%,光照强度80~100μmol·m-2·s-1时PUFA高达40.22%~40.56%;MP-2生长的适宜盐度为10~40,最适盐度25,高盐有利总脂的积累,盐度30~35时总脂含量高达36.54%~36.66%,低盐有利EPA和PUFA积累,盐度为10~15时EPA高达31.31%~31.46%,盐度15时PUFA最高(44.75%)。     

Effects of light intensity distribution on growth of Rhodobacter capsulatus

For cultivation of photosynthetic cells under defined light intensity distributions, the repeated batch culture, in which a part of culture broth containing grown cells was repeatedly replaced at predetermined time intervals with a fresh medium to keep the cell concentration constant at an initial value, was employed. By use of this method the effects of the light intensity distribution on the growth characteristics of Rhodobacter capsulatus were studied. Unexpected decreases in the specific growth rate were observed in culture of R. capsulatus at high cell concentrations and a long light path length. Big differences in the light intensities of lightly and darkly illuminated portions in photobioreactors, which reflects the light intensity distribution, seemed to cause this phenomenon, which must be taken into consideration for stable growth of photosynthetic cells.     

Effect of light intensity on the growth of Azolla pinnata R. Brown at Ranchi,India

Light intensity has a profound effect on the growth of Azolla pinnata R. Brown. Fresh weight, dry weight and moisture content were maximum at 80 000 lux, but maximum frond area was attained in 50% light intensity. There was a wide variation in frond colour under different treatments. Frond texture, root characteristics and sporocarp production were also affected. The plant expresses heliophytic characteristics.     

Effect of light intensity on broiler behaviour and diurnal rhythms

Light intensity manipulation is an important management tool affecting broiler behaviour and physiology but still there is a debate regarding the optimum level to be used in confinement barns. Two experiments were completed to study the impact of light intensity (1, 10, 20 and 40 lx) on behaviour and diurnal rhythms of broilers raised to 35 d of age. For each experiment, 950 Ross × Ross 308 chicks were housed per room with replication of individual light intensity treatment in two environmentally controlled rooms. Within each large room, a small pen with 25 male and 25 female chicks was used for recording behaviour. Data were analyzed as a randomized complete block design with experiment acting as a block. All chicks were provided with 40 lx intensity and 23 h light until shifting to treatment light intensity and 17 h daylength at 7 d of age. For each replicate, behaviour was recorded for a 24 h period, starting at 16 or 17 d of age. At 23 d of age, three birds per room were bled at the start, middle and end of light and dark periods for melatonin estimation using RIA. When summarized over the 24 and 17 h observation periods, birds exposed to a light intensity of 1 lx rested more (P = 0.01) and preened (P < 0.05) and foraged (P < 0.05) less in comparison to other light intensities. Birds from all treatments exhibited diurnal rhythms for feeding, resting, drinking, walking, standing, foraging and preening behaviours with little or no activity during the 7 h dark phase. The serum melatonin levels at the start, middle and end of light and dark phases were unaffected by light intensity (P > 0.1). In conclusion, light intensity ranges from 1 to 40 lx did not affect melatonin levels or behavioural diurnal rhythms, but birds exposed to a light intensity of 1 lx rested more and preened less, potentially indicating a reduced welfare state.     

Effect of temperature on nitrification intensity in soil

The temperature dependence of nitrification can be expressed by the Arrhenius equation while the time course of nitrate production can be expressed by the Gomperz function. These two findings served as a basis for a mathematical model which makes it possible to calculate nitrate production in the soil even when the temperature changes once or more times during the incubation.     

Effect of light intensity on sporulation of Botryosphaeria ribis

Pycnidia were produced by six of seven isolates ofB. ribis at one or more intensity levels of continuous illumination at 21 °C. Under conditions of alternating light (12 h–27 °C) and darkness (12 h–21 °C) pycnidia formed in cultures of six isolates at three or more intensity levels, while one isolate failed to form pycnidia at any intensity level. Pycnidia did not develop when cultures were incubated in complete darkness. Exposure periods as brief as 2 days under continuous illumination at 21 °C induced pycnidial formation. In alternating light (12 h–27 °C) and darkness (12 h–21 °C), the shortest period of exposure which induced pycnidial formation was 4 days. Continuous illumination at 21 °C favored development of uniloculate pycnidia, while alternating light (12 h–27 °C) and darkness (12 h–21 °C) favored formation of multiloculate pycnidia.Contribution No. 22 from The Botany Section of The Department of Biology, The Pennsylvania State University.     

Effect of light intensity on macromolecular synthesis in cyanobacteria

The light-dependent incorporation of NaH¹⁴CO₃ into low molecular weight compounds, polysaccharide, or protein was determined in cultures of the cyanobacteriumMerismopedia tenuissima incubated at a series of light intensities. There was an inverse relationship between incorporation into polysaccharide and protein. At light intensities of 90 E/m²/sec or above, relative incorporation of radioisotope into polysaccharide was greatest and relative incorporation into protein was lowest. Optimal relative protein accumulation occurred in samples incubated at 20 E/m²/sec. A broader optimum of light intensity for maximal protein accumulation was found if ammonia rather than nitrate was the nitrogen source. Physiological adaptation of cultures to growth at a particular light intensity did not alter the pattern of macromolecular incorporation when those cultures were tested over the series of light intensities. The response of cultures ofOscillatoria rubescens to light intensity was similar to that ofM. tenuissima, although incorporation into low molecular weight compounds was significantly greater.The effect of light intensity on macromolecular synthesis in a natural population ofOscillatoria rubescens was also determined. A pattern similar to that observed in batch cultures ofO. rubescens was occasionally found, but in other experiments there was no increase in relative protein incorporation when light intensity was decreased.