Search

The variation in Skeletonema cells grown at 3 klux continuous illumination and 20°C is reported. Four different types of lamps gave no difference in the photosynthetic characteristics. The average diameter of the cells decreased from 8-3.5 μ during their six months vegetative period. The ratio between the pigment content in the largest and the smallest cells was about 2:1. A good correlation between cell volume and chlorophyll a content was found for this species. The content of chlorophyll c generally varied between 4 and 17 per cent of the chlorophyll a content -- A distinct correlation between the chlorophyll a content and the rate of photosynthesis per unit of cells at low light intensity was found. The rate of photosynthesis, in mg C per mg chlorophyll a and hour at 1 klux, varied between 0.40 and 0.70 for all 60 experiments with an average value of 0.56. The corresponding value for cells deficient in phosphorus was 0.19 and for cells deficient in nitrogen 0.09. -- The material also showed a good correlation between the rate of photosynthesis per cell at 1 klux and the light-saturated rate of photosynthesis. Ik varied between 7 and 13 klux. [ABSTRACT FROM AUTHOR]

Two types with regard to adaptation to different light intensities are described: The Chlorella type and the Cyclotella type. The Chlorella type is mostly found among the green algae, the Cyclotella type among the diatoms. The Chlorella type adapts to a new light intensity mainly by changing the pigment content. Therefore the cells adapted to a high light intensity have a lower chlorophyll a content per cell than cells adapted to a low light intensity. Light saturation is mostly rather low for cells adapted to low light intensities. The light-saturated rate of photosynthesis ist mostly lower for cells adapted to a high light intensity than for cells adapted to a low light intensity. The actual photosynthesis is not much higher at a high light intensity than at a low one. The actual photosynthesis is the photosynthesis at the light intensity where the cells are grown. — The Cyclotella type adapts only by changing the light-saturated rate. The chlorophyll content is the same in cells grown at low and high light intensities. Light saturation for cells grown at a low light intensity is rather high. The light-saturated rate is much higher in the case examined at the high light intensity than at the low one. The actual photosynthesis is considerably higher for cells grown at high light intensities than for cells grown at low light intensities. — The two adaptation types are not sharply separated since transition types occur. [ABSTRACT FROM AUTHOR]

A survey of the adaptation of plankton algae in Nature to different light intensities and temperatures is given. The adaptation is always important for the plankton populations at all depths. However, the shade adaptation of the algae in the lower part of the photic zone is often of relatively little importance for the integral primary production per unit of surface, except on the by no means rare occasions when the hulk of the algae is found in this lower part. It is shown that the Ik of surface plankton during summer in the Arctic is high despite the low temperatures present. This is due to an increase of the enzyme quantities per cell. Daily fluctuations in Ik are due partly to photooxidation, partly to the fact that the periods for the production of chlorophyll and photosynthetic enzymes are mutually displaced. Despite the daily fluctuations in Ik the difference between "sun" phytoplankton and "shade" phytoplankton is distinct. [ABSTRACT FROM AUTHOR]

The theory that Skeletonema cells adapt to lower temperatures by increasing their enzyme concentration, is supported by various facts. While the rates of photo- synthesis are identical in cells adapted to different temperatures (7-20°C) the growth rate decreases with decreasing temperature and the production of organic matter increases with decreasing temperature. Further, the concentration of protein per cell and the height of the cells increase with decreasing temperature. [ABSTRACT FROM AUTHOR]

A culture of Skeletonema costatum grown at a light intensity of 3 klux and at 20°C was synchronized in diurnally intermittent illumination of 12 hour light and 12 hour dark. The culture was hardly fully synchronous as the cell division period lasted about 9 hours. The cell division started in the middle of the light period. The concentration of the pigments: chlorophyll a, chlorophyll c and fucoxanthin and the rate of light-saturated photosynthesis were followed every hour during the 24 hour period. Both the concentration of pigments and the photosynthetic activity showed a rhythmical variation. The concentration per cell of all three pigments examined increased during the development of the cells and decreased automatically during the period of cell division. An increase in the pigment concentration was found only in the light period. The rate of light-saturated photosynthesis calculated per unit of cell number increased during the cell development and decreased during (tie division period. The increase in the photosynthetic activity at light-saturation started about 4 hours after the end of cell division, which was 4 hours before the light was turned on while the increase in the concentration of chlorophyll a first started 1-2 hours after this moment. The variation in photosynthetic activity was compared with that found by other workers. The results found with Chlorella ellipsoidea by Japanese scientists (Nihei et al.) was explained as an inhibition phenomenon because the cells were not adapted to the experimental conditions. [ABSTRACT FROM AUTHOR]

In a culture of the fresh water diatom Cyclotella Meneghiniana the average cell volume decreased with time due to reduction of the diameter of the valves. The rate of photosynthesis as a function of light intensity was determined for cells with different average cell volume and the chlorophyll a concentration in the cells was measured at the same time. It was found that the concentration of chlorophyll a in the different cells was approximately constant and independent of the cell volume. The rate of photosynthesis per number of cells at a light intensity of 1 Klux was nearly constant and this was also the case for the rate of photosynthesis calculated per unit of chlorophyll a at 1 Klux. The light saturated rate of photosynthesis per number of cells decreased with decreasing cell volume, but only slightly compared to the reduction in cell volume. The rate of photosynthesis per chlorophyll a and hour at a light intensity of 1 Klux varied in the experiments with Cyclotella between 0.28 and 0.41 mg C. The values are in good agreement with the determinations in green leaves deficient in chlorophyll and with determinations on Chlorella vulgaris carried out by other authors. It is suggested that the invariability of the chlorophyll a content in the cells with varying cell volume is due to a decrease in the cell vacuole with decreasing cell volume while the volume of cytoplasma in the cells is nearly unchanged. [ABSTRACT FROM AUTHOR]

Light-photosynthesis curves for cells adapted to 3 Klux and 30 Klux respectively, were studied using the freshwater diatom Cyclotella Meneghiniana. The initial slope of the curves for the two light intensities was the same which is due to the same concentration of chlorophyll in cells grown at 3 and 30 Klux. The light saturated rate per cell was about 40 per cent higher in 30 Klux-cells than in 3 Klux-cells. The amplitude in light adaptation was found to be rather small in Cyclotella. Ik for the light-photosynthesis curves for 3 Klux- and for 30 Klux-cells was 9 Klux and 12 Klux, respectively. In Chlorella vulgaris a much wider amplitude is found. The corresponding IK-values are 4 Klux and 13 Klux. The light adaptation from one light intensity (3 Klux) to another (30 Klux) or back again was found to be a rather rapid process. Already after 24 hours the adaptation to the new light intensity was complete. Cells of Cyclotella were found to be able to withstand light of very high intensity. Cells adapted to 3 Klux and placed at 30 Klux for three hours did not exhibit any of the inhibition of the rate of photosynthesis shown by cells of Chlorella vulgaris. On the contrary the light saturated rate goes up to a level about 30 per cent higher than that for the 3 Klux and place at 30 Klux for three hours did not exhibit any of the inhibition of the rate of photosynthesis shown by cells of Chlorella vulgaris. On the contrary the light saturated rate goes up to a level about 30 per cent higher than that for the 3 Klux-cells. Towards light intensities of 60 or 100 Klux cells of Cyclotella react in a similar way. No inhibition of the rate of the photosynthesis was found at these very high light intensities either. [ABSTRACT FROM AUTHOR]

Paper chromatograms of ether and ethanol extracts of cells of the three algal species: Chlorella vulgaris, Scenedesmus quaddricauda and Chlamydomonas reinhardi were tested on agar plates with the bacteria Bacillus subtilis. Inhibition zones were found at the starting line of the paper chromatograms as well as at the solvent front. The inhibition zone at the starting line only occurred after illumination and was due to a light-induced transformation of chlorophyllides. The inhibition zones at the solvent front were caused by two different kinds of substances. The first substance was, like chlorophyllides, a derivative of chlorophylls and only showed inhibiting action after illumination. The second substance had no relation to plant pigments. In extracts from Chlamydomonas it acted only after illumination, but in extracts from Chlorella and Scenedesmus it produced inhibition zones both in the light and the dark. By extraction of culture solutions from the three algal species chlorophyllides were found in the extracts which produced substances inhibiting the growth of Bacillus subtilis both in dark and light. It is suggested that chlorophyllides play a part as an antibacterial substance in natural waters. [ABSTRACT FROM AUTHOR]

Curves showing the rate of photosynthesis as a function of light intensity are presented for Chlorella vulgaris growing at a constant light intensity of either 3 or 30 Klux. The rate is given a) per number of cells, b) per unit of weight of chlorophyll (a + b), and c) per unit of wet volume or unit of weight of dry matter. At an illumination of about 3 Klux the average cell size is at its maximum. At the same time the content of chlorophyll per cell is maximal and the content of enzymes active in photosynthesis is very nearly maximal. If we increase the illumination the cell size decreases. At the same time the content of active enzymes per cell increases slightly, but the content of chlorophyll per cell decreases. If we decrease the illumination (from 3 Klux) cells are produced with the maximum content of chlorophyll but decreasing content of enzymes active In photosynthesis. At the same time the cell size decreases. Growth rates at the two light intensities are computed by means of the measured rates of photosynthesis and respiration. They are identical with the growth rates measured by means of the increase in number of cells. After a shift from 3 Klux to 30 Klux it takes only 24 hours before the ratio chlorophyll a+b: dry weight has changed to that normally found at the high light intensity. The same is true concerning the cell size. When shifting from 30 Klux to 3 Klux it takes a little longer. However, a chlorophyll concentration nearly as high as that ordinarily found at 3 Klux was measured. About 36 hours after the shift from 30 Klux to 3 Klux, or vice versa, the shape of the curve giving the rate of photosynthesis as a function of light intensity approaches that characteristic of algae grown constantly at the new light intensity. If Chlorella grown constantly at 30 Klux are transferred to the dark for 22 hours the shape of the tight photosynthesis curve is only moderately changed. IK decreases from 13 to 9 Klux. If instead the algae are transferred to 3 Klux, IK is decreased to 5 Klux after 22 hours. The importance is stressed of using such dilute concentrations of algae in experiments of both growth and photosynthesis that no self shading takes place. [ABSTRACT FROM AUTHOR]

Filtered culture solutions from cultures of different unicellular algae, especially Chlorella vulgaris, were tested for content of growth affecting substances using the bacteria Staphylococcus aureus as test organism. Either a decrease or an increase of the growth of the bacteria could be found. It was observed that both growth accelerating and growth inhibiting substances were present simultaneously in the culture solution and that the concentration of the substances varies a great deal in cultures of the same algal species even if the cultures were grown under apparently identical conditions. In one of the experiments the inhibiting effect was decreased by heating the algal filtrate at 70°C for 20 min. In another experiment at least two inhibitors were found. One was inactivated by illumination of the algal filtrate, a second was absorbed to Norit. [ABSTRACT FROM AUTHOR]

The growth of Staphylococcus aureus together with some bacteria isolated from contaminated algal cultures was studied in daylight and in light from fluorescent and incandescent lamps and compared with the growth in the dark. Light from incandescent lamps was found to have no effect on the growth of the bacteria. Daylight and fluorescent light had a distinct inhibiting effect on the growth rate of the bacteria studied. It is suggested that the effect may be due to light in the violet region of the spectrum. [ABSTRACT FROM AUTHOR]

Experiments were carried out with algae in mixed cultures (two species cultures) or with algae cultured in filtrates from cultures of other algae or the same species. In experiments with Asterionella formosa and Nitzschia palea it was shown that both species formed substances which inhibited the growth of the other species and that the rate of inhibition was very dependant on the experimental circumstances. It was shown further that Nitzschia formed autotoxic substances and it was suggested that Asterionella formed substances which accelerated the growth of other Asterionella cells and of Nitzschia in some cases. In experiments where Nitzschia was cultured in filtrates from Scenedesmus quadricauda and Chlorella pyrenoidosa cultures, it was shown that Scenedesmus formed substances which considerably inhibited the growth of Nitzschia. The growth of Nitzschia was not inhibited in filtrates from a 4-8 days old Chlorella culture but was distinctly so in filtrates from a 13-17 days old Chlorella culture. When Chlorella was cultured for 3 days in filtrates from a 21 days old Scenedesmus culture a marked inhibition of the growth was found. During 3 days of culturing of Chlorella in filtrate from a 21 days old Nitzschia culture an acceleration of the growth of Chlorella took place. Similarly an inhibition of the growth was found when Scenedesmus was cultured for 3 days in filtrates from a 21 days old Scenedesmus culture. On the other band, an acceleration of the growth of Scenedesmus took place when it was cultured in filtrates from a 21 days old Chlorella and a 21 days old Nitzschia culture, respectively. [ABSTRACT FROM AUTHOR]

Investigations of the plankton diatoms in lakes and planktonic and epiphytic diatoms in cultures have shown that the silica content in the cells depends on the number of cells, and the silica content is inversely proportional to the number of cells. This is the case both in ordinary cultures where the Si-concentration and the concentration of other nutrient salts are decreasing when the number of cells increase and in cultures with a flowing culture solution. The decrease in the silica content is probably caused by diatoms giving off a substance to the water which inactivates the silica assimilation. [ABSTRACT FROM AUTHOR]

Experiments carried out with the diatoms Nitzschia linearis and Thalassiosira nana show that the silicon in the cell walls is soluble in water and that the rate of solubility depends on the pH of the solution. The rate increases with increasing pH. At pH 8 not much more than 5 per cent of the silicon in the cells was dissolved in both species during the experiments, at pH 10 Thalassiosira was dissolved completely. In the case of Nitzschia linearis 20 per cent of the silicon was dissolved at pH 10 during the experiment. Thus the silicon compounds are found in the diatom cells in forms which arc hydrolyzed at different rates. The silicon compounds in Thalassiosira are easy to hydrolyze at pH 10. In Nitzschia linearis some parts are easy to hydrolyze, others very difficult. [ABSTRACT FROM AUTHOR]

Two experiments with Nitzschia palea and with Bacillaria paradoxa, respectively, are described. The diatoms were cultivated in plastic containers of polystyrene. In each experiment three series with different initial Si-concentrations were carried out (0.3, 1.8, and 5.3 mg Si and 0.8, 1.8, and 5.8 mg Si per liter). 24 containers in each series were used. The growth was determined by the increase in chlorophyll content, in some cases also by the number of cells. The Si-concentrations were determined during the experiments with the methods described. In both experiments the Si-concentration decreased rapidly to a level of 30- 40 μg Si per liter independently of the initial Si-concentration, and then further uptake took place only very slowly. In Experiment 1 concentrations down to 15-20 μg Si and in Experiment 2 down to 5(0)--10 μg Si per liter were found at the termination of the experiments. The growth of Nitzschia palea (increase of chlorophyll content and number of cells) stopped or nearly stopped when the Si-concentration of 30-40 ug Si per 1 was reached. The same was the case in Experiment 2 with Bacillaria paradoxa concerning the increase of number of cells, but in this experiment on the other hand the increase in chlorophyll content continued to the termination of the experiment. Through investigations in some Danish eutrophic lakes the author found that the Si-concentration decreases to a similar level as found in the experiments, 30-40 μg Si per liter during the diatom maxima. [ABSTRACT FROM AUTHOR]