Photosynthesis and growth rates of Laurencia brongniartii J. Agardh (Rhodophyta, Ceramiales) in preparation for cultivation

Laurencia brongniartii is usually found at depths below 4 m, but can be found in shallow subtidal areas in crevices and on the walls of a coral reef in Amami Oshima Island, Kagoshima Prefecture, Japan, where irradiances were significantly lower than those at similar depths in open water. In preparation for the possible cultivation of this species for its antibiotic compounds, the effects of temperature and irradiance on photosynthesis and growth were measured. Photosynthesis and growth rates of L. brongniartii explants were highest at 26 and 28 °C, which closely corresponded to temperatures found during August to late December when it was most abundant. The estimated maximum photosynthesis rate (P _max) was 4.41 mol photon m^–2 s^–1 at 26 °C and 4.07 mol photon m^–2 s^–1 at 28 °C. Saturating irradiance occurred at 95 mol photon m^–2 s^–1 at 26 °C and 65 mol photon m^–2 s^–1 at 28 °C. In contrast, growth experiments at 41.7 mol photon m^–2 s^–1 caused bleaching of explants and the maximum growth rate observed during the study was 3.02 ± 0.75% day^–1 at 28 °C and 25 mol photon m^–2 s^–1. The difference in the saturating irradiance for photosynthesis and the irradiance that caused bleaching in growth experiments suggests that long-term exposure to high irradiance was detrimental and should be addressed before the initiation of large scale cultivation.     

Effects of pre-storage conditions on storage of in vitro cultures of Nephrolepis exaltata (L.) Schott and Cordyline fruticosa (L.) A. Chev.

In vitro cultures of Nephrolepis exaltata and Cordyline fruticosa were stored at 5°, 9° or 13°C, at a low irradiance (3–5 mol m^–2 s^–1) or in darkness. Prior to storage the cultures were subjected to 18°, 21°, 24° or 27°C and 15, 30 or 45 mol m^–2 s^–1 in a factorial combination.The optimal storage conditions for Nephrolepis were 9°C in complete darkness. These cultures were still transferable to a peat/perlite mixture at the end of the experimental period of 36 months.The optimal storage conditions for Cordyline were 13°C and a low light level (±3–5 mol m^-2 s^-1). When the pre-storage conditions were normal growth room conditions (24°C and 30 mol m^-2 s^-1), in vitro cultures could be stored for 18 months. With the most favourable pre-storage treatment (18°C and 15 mol m^-2 s^-1) some cultures still had green shoots after 36 months of storage, but did not survive transfer to peat/perlite.Pre-conditioning before storage was most favourable for Nephrolepis, and not that important, but still favourable, for Cordyline. There was an interaction between pre-storage temperature and pre-storage irradiance. For both species a high irradiance level was less favourable than a low irradiance level when combined with high growth room temperatures.Abbreviations BA 6-benzyladenine - IAA indole-3-acetic acid - NOA 2-naphthoxyacetic acid     

Tolerance of Borya nitida,a poikilohydrous angiosperm,to heat,cold and high-light stress in the hydrated state

Borya nitida Labill., a plant able to colonize rock outcrops and shallow sands in areas of high incident solar radiation in Western Australia, was examined for its tolerance to extremes of temperature, and to intense visible radiation. Stress injury to the leaves from heat, chilling or photoinhibitory light was followed by the decrease in in-vivo variable chlorophyll fluorescence. Heat injury was also ascertained by an increase in the constant fluorescence. Borya nitida leaves were extremely heat tolerant when heated at 1° C min^-1. In-vivo variable chlorophyll fluorescence was detectable up to 55° C, several degrees higher than either maize or barley which are, respectively, adapted to warm and cool climates. An increase in constant fluorescence occurred above 50° C in B. nitida. This compares with values in the literature of 48–49° C for three desert plants from Death Valley, California, and 44–48° C for ten species of tropical plants. Unlike the Death-Valley plants, the high degree of heat tolerance found in B. nitida did not require prior acclimation by growth at high temperatures. Borya nitida was also tolerant of a chilling temperature of 0° C. Plants grown at a low photon fluence rate (120 mol m^-2s^-1) were irreversibly photoinhibited by light at 650 mol m^-2s^-1. Plants grown in sunlight resisted photoinhibition; however, the capacity to withstand photoinhibition was no greater than that of plants from less extreme environments.     

Effect of irradiance, temperature and salinity on growth and toxin production by Nodularia spumigena

The object of this work was to determine, using a full-factorial experiment, the influence of temperature, irradiance and salinity on growth and hepatotoxin production by Nodularia spumigena, isolated from Lake Alexandrina in the south-east of South Australia. Higher levels of biomass (determined as particulate organic carbon, POC), toxin production and intracellular toxin concentration per mg POC were produced under light limited conditions (30 mol m^–2 s^–1) and at salinities equal to or greater than those experienced in Lake Alexandrina. Both highest biomass and total toxin production rates were recorded at temperatures equal to or greater than those of the lake (20 and 30°C). The temperature at which maximum biomass and toxin production was recorded decreased from 30°C for cultures grown at 30 mol m^–2 s^–1 to 20°C when grown at 80 mol m^–2 s^–1. In contrast, intracellular toxin per mg POC was highest at the lowest growth temperature, 10°C, at both 30 and 80 mol m^–2 s^–1. It appears that the optimum temperature for biosynthetic pathways used in the production of toxin is lower than the optimum temperature for those pathways associated with growth. Intracellular toxin levels were higher in cells cultured at 10°C/30 mol m^–2 s^–1 whereas the majority of the toxin was extracellular in cells grown at 30°C/30 mol m^–2 s^–1. This implies that the highest concentration of toxin in lake water would occur under high temperature and high irradiance conditions. Individual environmental parameters of salinity, irradiance and temperature were all shown to influence growth and toxin production. Notwithstanding, the overall influence of these three parameters on toxin production was mediated through their effect upon growth rate.     

Growth of the thermotolerant yeast,Candida valida,on ethanol: Dependences of maximal growth rate and cell biomass yield on temperature

Summary Growth of Candida valida on ethanol in pH-auxostat and chemostat has been studied. Maximal growth rate, _m, and cell biomass yield, Y _s, display the Arrhenius dependence on temperature within the ranges 18°–30° C and 30°–36° C and an abrupt fall above 36° C. The temprature dependence of both parameters has breaks at 30° C and 36° C. Activation energies have been measured for both _m and Y _s. The reason for a weaker effect of temperature on Y _s than on _m is discussed.     

Photoinhibition of photosynthesis in intact bean leaves: role of light and temperature,and requirement for chloroplast-protein synthesis during recovery

Photoinhibition of photosynthesis was induced in intact leaves of Phaseolus vulgaris L. grown at a photon flux density (PFD; photon fluence rate) of 300 mol·m^-2·s^-1, by exposure to a PFD of 1400 mol·m^-2·s^-1. Subsequent recovery from photoinhibition was followed at temperatures ranging from 5 to 35°C and at a PFD of either 20 or 140 mol·m^-2·s^-1 or in complete darkness. Photoinhibition and recovery were monitored mainly by chlorophyll fluorescence emission at 77K but also by photosynthetic O₂ evolution. The effects of the protein-synthesis inhibitors, cycloheximide and chloramphenicol, on photoinhibition and recovery were also determined. The results demonstrate that recovery was temperature-dependent with rates slow below 15°C and optimal at 30°C. Light was required for maximum recovery but the process was light-saturated at a PFD of 20 mol·m^-2·s^-1. Chloramphenicol, but not cycloheximide, inactivated the repair process, indicating that recovery involved the synthesis of one or more chloroplast-encoded proteins. With chloramphenicol, it was shown that photoinhibition and recovery occurred concomitantly. The temperature-dependency of the photoinhibition process was, therefore, in part determined by the effect of temperature on the recovery process. Consequently, photoinhibition is the net difference between the rate of damage and the rate of repair. The susceptibility of chilling-sensitive plant species to photoinhibition at low temperatures is proposed to result from the low rates of recovery in this temperature range.Abbreviations and symbols Da Dalton - Fo, Fm, Fv instantaneous, maximum, variable fluorescence emission - PFD photon flux density - PSII photosystem II - photon yield C.I.W.-D.P.B. Publication No. 871     

Laccase from the medicinal mushroom Agaricus blazei: production, purification and characterization

The medicinal mushroom Agaricus blazei produced high amounts of laccase (up to 5,000 units l^–1) in a complex, agitated liquid medium based on tomato juice, while only traces of the enzyme (<100 units l^–1) were detected in synthetic glucose-based medium. Purification of the enzyme required three chromatographic steps, including anion and cation exchanging. A. blazei laccase was expressed as a single protein with a molecular mass of 66 kDa and an isoelectric point of 4.0. Spectroscopic analysis of the purified enzyme confirmed that it belongs to the blue copper oxidases. The enzymes pH optimum for 2,6-dimethoxyphenol (DMP) and syringaldazine was pH 5.5; but for 2,2-azino-bis(3-ethylthiazoline-6-sulfonate) (ABTS) no distinct pH optimum was observed (highest activity at the lowest pH tested). Purified laccase was stable at 20°C, pH 7.0 and pH 3.0, but rapidly lost its activity at 40°C or pH 10. Sodium chloride strongly inhibited the enzyme activity, although the inhibition was completely reversible. The following kinetic constants were determined (K_m, k_cat): 63 M, 21 s^–1 for ABTS, 4 M, 5 s^–1 for syringaldazine, 1,026 M, 15 s^–1 for DMP and 4307 M, 159 s^–1 for guaiacol. The results show that—in addition to the wood-colonizing white-rot fungi—the typical litter-decomposing basidiomycetes can also produce high titers of laccase in suitable liquid media.     

Development, survival and reproduction of Euseius finlandicus (Acari: Phytoseiidae) at different constant temperatures

Development, survival and reproduction of Euseius finlandicus Oudemans were studied at seven constant temperatures (15, 20, 25, 27, 30, 32 and 34°C) in the laboratory. Within the temperature range tested, developmental period from egg to adult varied from 148 to 360.5h and 133.7 to 336.5h for females and males, respectively. The lower thermal threshold for immature development for females and males was 8.9 and 6.4°C, respectively. Survival during immature development exceeded 90% at all the temperatures from 15 to 32°C, but at 34°C an abrupt decline was recorded. Female longevity decreased gradually from 82.7d at 15°C to 12.2 d at 34°C. The mean generation time ranged from 44.3d at 15°C to 15.9d at 32°C. The highest r _m value (0.2817) was obtained at 30°C and the lowest at 15°C (0.0976). Temperatures above 30°C had an adverse effect on population increase.     

The life cycle of Laminaria abyssalis (Laminariales,Phaeophyta) in culture

Laminaria abyssalis occurs in deep water in tropical latitudes of the Brazilian coast (19° 23 S, 38° 28 W to 22° 54 S, 42° 13 09 W). Its life cycle has been completed in the laboratory in seven months using different conditions of light and temperature. The gametophytic stage required for growth the low photon flux density of 1.2 ± 0.3 µmol m^–2 s^–1 and 18 °C, while the juvenile and adult sporophytes needed 15 µmol m^–2 s^–1 and 18 °C. The sporophytes became fertile at 23 °C. Our results showed that light and temperature are the main factors regulating the growth and life history of this species under the culture conditions tested.     

Respiration rates of Chiloplacus sp. and other arctic nematodes at low and high temperatures

Summary Respiration of an undescribed species of soil nematode of the genus Chiloplacus from the Canadian High Arctic was measured at 2°, 5°, 10°, 15°, 20° and 25°C. The corresponding metabolic rates were 0.2697×10^-3 l, 0.3406×10^-3 l, 0.8408×10^-3 l, 0.8539×10^-3 l, 1.8420×10^-3 l and 2.9360×10^-3 l O₂ ind^-1 h^-1, respectively, for a nematode of 1.0 g dry weight. The relationship between respiration and dry weight for Chiloplacus sp. at 10°C is described by the function log R=-3.0693+0.8844 log W. Q₁₀ values for the 2°–5°, 5°–10°, 10°–15°, 15°–20° and 20°–25°C temperature intervals were 2.18, 6.09, 1.03, 4.65 and 2.54, respectively. Chiloplacus sp. showed raised metabolic rates at low tempetatures compared with species from warmer environments. Metabolic rates of representative samples of the soil, nematode fauna (dominated by individuals of the genus Plectus) from the same location were 0.1593×10^-3 l, 0.3603×10^-3 l and 0.5332×10^-3 l O₂ ind^-1 h^-1 at 5°, 10° and 15°C for an average nematode of 0.4297 g dry weight.     

The kinetics of photoinhibition and its recovery in the red alga Porphyridium cruentum

When Porphyridium cruentum cells were illuminated with high fluence rate between 1900 and 4800 mol photons m^-2s^-1, a decrease in the photosynthetic activity of the cells was observed. Within the time frame of 20 min, and under the fluence rates studied, the sum of photons to be absorbed by cells (mg of chlorophyll (Chl), sufficient to initiate photoinhibition was calculated to be 9235.8 mol. The minimal specific light absorption rate to initiate photoinhibition in P. cruentum ranges between 2.29 and 4.26 mol photons s^-1 mg^-1 chl.a. There was a linear relationship between the specific rate of photoinhibition and the specific light absorption rate. A photon number of 2.56×10⁴ mol mg^-1 chl.a photoinhibited photosynthesis instantaneously. At 15°C, no photoinhibitory effect was observed at 2300 mol photons m^-2 s^-1 even after 45 min of illumination. At the other extreme of 35°C, 84% inhibition of photosynthetic activity was observed within 10 min of exposure to 2300 mol photons m^-2 s^-1. Between 20 and 30°C, the photoinhibitory effect was comparable. Photoinhibited P. cruentum cells recovered readily when transferred to low light (90 mol photons m^-2 s^-1) and darkness, and the specific rate of recovery was independent of the light intensity to which the cells were exposed, during the photoinhibitory treatment.Abbreviations Chlorophyll QL, specific light absorption rate Publication No. 28 of the Microalgal Biotechnology Laboratory     

Photosynthetic response of Prorocentrum mariae-lebouriae (Dinophyceae) to different spectral qualities,irradiances, and temperatures

Photosynthetic productivity (P_s) of the estuarine dinoflagellate Prorocentrum mariae-lebouriae (Parke and Ballantine) comb. nov., was measured with an open differential infra-red gas analysis system especially designed to measure CO₂ uptake at a constant CO₂ concentration. P_s was determined in six different fluorescent lamp spectral qualities (SQ) (daylight, blue, green, orange, orange-red and red) with bandwiths ranging from 50 to 75 nm and at photon flux densities (PFD) from 1.7 to 170 mol of quanta s^–1 m^–2 to characterize the spectral response of daylight SQ grown P. mariae-lebouriae cultures. P_s was significantly higher for blue irradiation than for any other SQ. Compared to blue (100%) the following mean values were found: daylight 88%, green 79%, orange 29%, orange-red 56%, and red 87%. Differences were greatest at low PFD. Most measurements were performed at 20°C, but P_s was found to vary as a direct function of the culture temperature. A 10°C increase in temperature caused a 50% increase in P_s from 10° to 30°C with saturating PFD. Since the analytical system measured very small CO₂ differentials, down to 0.5 l l^–1, we were able to detect small and fast CO₂ transients at the beginning and end of an irradiation. These transients, known as CO₂-burst and CO₂-gulp, increased in magnitude with increased PFD.     

Mathematical modeling of mixing in a horizontal rotating tubular bioreactor: “Spiral flow” model

A horizontal rotating tubular bioreactor (HRTB) was designed as a combination of a thin-layer bioreactor and a biodisc reactor whose interior was divided by O-ring shaped partition walls. For the investigation of mixing in HRTB the temperature step method was applied. Temperature changes in the bioreactor were monitored by six Pt-100 sensors (t ₉₀ response time 0.08 s and resolution 0.002 °C) which were connected with an interface unit and a personal computer. In this work a modified tank in series concept was used to establish a mathematical model. The heat balance of the model compartments was established according to the physical model and the spiral flow pattern. Numerical integration was done by the Runge-Kutta-Fehlberg method. The mathematical mixing model called spiral flow model contained four adjustable parameters (N1, Ni, F _cr and F _p) and five parameters which characterized the plant and experimental conditions. The spiral flow model was capable to describe the mixing in HRTB properly, and its applicability was much better than with the simple flow model, presented earlier.List of Symbols A _ui m² ithpart of inner surface of bioreactor's wall - A _vi m² ith part of outlet surface of bioreactor's wall - C _p kJ kg^–1 K^–1 heat capacity of liquid - c _pr kJ kg^–1 K^–1 heat capacity of bioreactor's wall - D h^–1 dilution rate - E °C°C^–1h^–1 error of mathematical model - F _cr dm³ s^–1 circulation flow in the model - F _p dm³s^–1 back flow in the model - F _t dm³ s^–1 inlet flow in bioreactor - I °C intensity of temperature step, the difference in temperature between the temperature of the inlet liquid flow and the temperature of liquid in bioreactor before temperature step - K1 Wm^–2 K ^–1 heat transfer coefficient between the liquid and bioreactor's wall - K2 Wm^–2 K ^–1 heat transfer coefficient between the bioreactor's wall and air - L m length of bioreactor - m _s kg mass of bioreactor's wall - n min^–1 rotational speed of bioreactor - n _s number of temperature sensors - N1 number of cascades - Ni number of compartments inside cascade - r _u m inner diameter of bioreactor - r _v m outside diameter of bioreactor - s(t) step function - t s time - T °C temperature - T _c °C calculated temperature - T _m °C measured temperature - T _N 1,Ni°C temperature of liquid in defined compartments inside the cascade - T _N 1,S°C temperature of defined part of bioreactor's wall - T _N i,z°C temperature of surrounding air - V _t dm³ volume of liquid in the bioreactor     

Purification and characterization of a thermostable β-galactosidase with high transgalactosylation activity from Saccharopolyspora rectivirgula

We purified an extracellular thermostable -galactosidase of Saccharopolyspora rectivirgula strain V2-2, a thermophilic actinomycete, to homogeneity and characterized it to be a monomeric enzyme with a relative molecular mass of 145 000 and s°_20,w of 7.1 s. In addition to the hydrolytic activity of 1-O-substituted -d-galactopyranosides such as lactose [a Michaelis constant K _m=0.75 mm and molecular activity (k _cat)= 63.1 s^–1 at pH 7.2 and 55° C] and p-nitrophenyl -d-galactopyranoside (K _m=0.04 mm k _cat= 55.8 s^–1), the enzyme had a high transgalactosylation activity. The enzyme reacted with 1.75 m lactose at 70°C and pH 7.0 for 22 h to yield oligosaccharides in a maximum yield (other than lactose) of 41% (w/w). A general structure for the major transgalactosylic products could be expressed as (Gal)_c-Glc, where n is 1, 2, 3, and 4 with a glucose at a reducing terminal. These oligosaccharides could selectively promote the growth of the genus Bifidobacterium found in human intestines. S. rectivirgula -galactosidase was stable at pH 7.2 up to 60°C (for 4 h in the presence of 10 m MnCl₂) or 70°C (for 22 h in the presence of 1.75 m lactose and 10 m MnCl₂). Thus the enzyme is applicable to an immobilized enzyme system at high temperatures (60°C <) for efficient production of the oligosaccharides from lactose. Correspondence to: T. Nakayama     

Influence of environmental factors on the growth in culture of a New Zealand strain of the fast-spreading algaHydrodictyon reticulatum (water-net)

Hydrodictyon reticulatum (L.) Lagerh. is a recent addition to the New Zealand flora and is expanding its distribution rapidly. Proliferations of the alga now constitute an economic nuisance in waters which have not previously suffered filamentous algal blooms. To better understand the current and likely future spread of the alga and to identify possible management options the alga's growth requirements have been investigated. A strain isolated from New Zealand tolerated temperatures between 5 and 40 °C and salinities from 0 to 5. Optimal growth was at 25 °C, 150 mol photon m^–2s^–1 and in freshwater. Nett photosynthesis was saturated at photon flux densities of 100 and 160 mol m^–2s^–1 at 12 and 20 °C, respectively. Growth rate was linearly related to internal N concentration and hyperbolically to internal P concentration. Minimum cellular nutrient contents, by weight, were 1% N and 0.2% P. Growth was saturated at contents of 5% N and 0.5% P under the conditions of culture (20 °C, 150 mol photon m^–2s^–1). The alga maintained optimal cellular N content at low ambient nitrate concentrations (100 mg m^–3) half optimum content at 18 mg m^–3. Affinity for filtrable reactive phosphorus was not unusually high compared to other filamentous algae. We suggest that this alga is occupying a niche in New Zealand which has been precluded from other filamentous nuisance algae by low N concentration and N:P ratio. The significance of these findings in setting environmental targets for management of this nuisance alga is discussed.Author for correspondence     

Leaf photosynthetic characteristics of seedlings of actinorhizal Alnus spp. and Elaeagnus spp.

Single leaf photosynthetic characteristics of Alnus glutinosa, A. incana, A. rubra, Elaeagnus angustifolia, and E. umbellata seedlings conditioned to ambient sunlight in a glasshouse were assessed. Light saturation occurred between 930 and 1400 mol m^-2s^-1 PAR for all species. Maximum rates of net photosynthesis (Pn) measured at 25°C ranged from 12.8 to 17.3 mol CO₂m^-2s^-1 and rates of dark respiration ranged from 0.74 to 0.95 mol CO₂m^-2s^-1. These values of leaf photosynthetic variables are typical of early to midsuccessional species. The rate of Pn measured at optimal temperature (20°C) and 530mol m^-2s^-1 PAR was significantly (p<0.01) correlated with leaf nitrogen concentration (r=0.69) and negatively correlated with the mean area of a leaf (r=–0.64). We suggest that the high leaf nitrogen concentration and rate of Pn observed for Elaeagnus umbellata and to a lesser degree for E. angustifolia are genetic adaptations related to their crown architecture.Abbreviations Pn net photosynthesis     

Feeding of Burbot, Lota lota, at Different Temperatures

Daily food intake of adult burbot, Lota lota, fed on vendace, Coregonus albula, were estimated experimentally at four different water temperatures (2.4, 5.1, 10.8 and 23.4°C). Mean daily food intake (MDI; g d^–1) and relative daily food intake (RDI; g g^–1 d^–1) increased with temperature from 2.4 to 10.8°C and decreased at 23.4°C. Temperatures of maximum daily food intake values were 13.6°C for MDI and 14.4°C for RDI. No correlation between food intake values and burbot weight was observed. RDI values were used to estimate annual food consumption of burbot population. Annual food consumption estimates were 9.7kg ha^–1 and 24.3kg ha^–1 when burbot biomass was 2.0 or 5.0kg ha^–1, respectively.     

Analysis of mutagenic DNA repair in a thermoconditional mutant of Saccharomyces cerevisiae. III. Dose-response pattern of mutation induction in UV-irradiated rev2ts cells

Summary Recent studies regarding the influence of cycloheximide on the temperature-dependent increase in survival and mutation frequencies of a thermoconditional rev2 mutant lead to the suggestion that the REV2-coded mutagenic repair function is UV-inducible. In the present study we show that stationary-phase rev2 ^ts cells are characterized by a biphasic linear-quadratic dose-dependence of mutation induction (mutation kinetics) of ochre alleles at 23° C (permissive temperature) but linear kinetics at the restrictive temperature of 36° C. Mathematical analysis using a model based on Poisson statistics and a further mathematical procedure, the calculation of apparent survival, support the assumption that the quadratic component of the reverse mutation kinetics investigated can be attributed to a UV-inducible component of mutagenic DNA repair controlled by the REV2 gene.     

Photosynthetic performance of transplanted ecotypes ofEcklonia cava(Laminariales, Phaeophyta)

Young sporophytes of short-stipe ecotype ofEcklonia cavafrom a warmer locality (Tei, Kochi Pref., southern Japan) and those of long-stipe ecotype from a cooler locality (Nabeta, Shizuoka Pref., central Japan) were transplanted in 1995 to artificial reefs immersed at the habitat of long-stipe ecotype in Nabeta Bay, Shizuoka Pref., central Japan. The characteristics of photosynthesis and respiration of bladelets of the transplanted sporophytes of the two ecotypes were compared in winter and summer 1997; the results were assessed per unit area, per unit chlorophyllacontent and per unit dry weight. In photosynthesis-light curves at 10–29 °C, light saturation occurred at 200–400 mol photon m^–2s^–1in sporophytes from both Tei and Nabeta. The maximum photosynthetic rate (P _max) at 10–29 °C and the light-saturation index (I _k) at 25–29 °C in sporophytes from both localities were generally higher in winter than in summer.P _maxat 25–29 °C (per unit area and chlorophylla) were higher in sporophytes from Tei than those from Nabeta in both seasons. The optimum temperature for photosynthesis was 25 °C in winter and 27 °C in summer at high light intensities of 100–400 mol photon m^–2s^–1. However, at lower light intensities of 12.5–50 mol photon m^–2s^–1, it was 20 °C in winter and 25–27 °C in summer for sporophytes from both locations. Dark respiration increased with temperature rise in the range of 10–29 °C in sporophytes from both locations in summer and winter. The sporophytes transplanted from Tei (warmer area) showed higher photosynthetic activities than those from Nabeta (cooler area) at warmer temperatures even under the same environmental conditions. This indicates that these physiological ecotypes have arisen from genetic differentiation.     

Growth and productivity of the psychrophilic marine diatoms Thalassiosira antarctica Comber and Nitzschia frigida Grunow in batch cultures at temperatures below the freezing point of sea water

Summary The diatoms Nitzschia frigida and Thalassiosira antarctica grow exponentially even at temperatures between-4 and -6°C and a salinity between 73 and 100 Under these conditions the light saturation of growth is reached in continuous light at a scalar quantum irradiance of between 7 mol·m^–2·s^–1 and 10 mol · m^–2 · s^–1. The increase in salinity retards growth more than a decrease in temperature. For N. frigida the limit of growth is at -8°C (S = 145%.). At increasing quantum irradiance, the chlorophyll content per unit cell volume decreases, whereas there is a significant increase in the carbon content of the exponentially growing cells. In addition, there is hardly any change in the protein content. The results show that both species of diatom can survive in ice without forming resting spores and even grow at extremely low temperatures.