Growth, greening, and phytochrome in etiolated spirodela (lemnaceae)

Two species of Spirodela were grown aseptically in a simple mineral medium containing sucrose. Weak red light (15 erg cm⁻² sec⁻¹) enhanced dark growth of S. oligorrhiza, whereas weak far red light (15 erg cm⁻² sec⁻¹) when given after the red light reduced this effect.     

Photosynthesis, Photorespiration and Respiration of Detached Spruce Twigs as Influenced by Oxygen Concentration and Light Intensity

The effects of oxygen concentration and light intensity on the rates of apparent photosynthesis, true photosynthesis, photorespiration and dark respiration of detached spruce twigs were determined by means of an infra-red carbon dioxide analyzer (IRCA). A closed circuit system IRCA was filled with either 1 per cent of oxygen in nitrogen, air (21 % O₂) or pure oxygen (100 % O₂). Two light intensities 30 × 10³ erg · cm ^?2· s^?1 and 120 × 10³ erg · cm^?2· s^?1 were applied. It has been found that the inhibitory effect of high concentration of oxygen on the apparent photosynthesis was mainly a result of a stimulation of the rate of CO₂ production in light (photorespiration). In the atmosphere of 100 % O₂, photorespiration accounts for 66–80 per cent of total CO₂ uptake (true photosynthesis). Owing to a strong acceleration of photorespiration by high oxygen concentrations, the rate of true photosynthesis calculated as the sum of apparent photosynthesis and photorespiration was by several times less inhibited by oxygen than the rate of apparent photosynthesis. The rates of dark respiration were essentially unaffected by the oxygen concentrations used in the experiments. An increase in the intensity of light from 30 × 10³ erg · cm^?3· s^?1 to 120 · 10³ erg · cm^?2· s^?1 enhanced the rate of photorespiration in the atmospheres of 21 and 100 % oxygen but not in 1 % O₂. The rate of apparent photosynthesis, however, was little affected by light intensity in an atmosphere of 1 % oxygen.     

Untersuchung der Beziehung zwischen Pigmentzusammensetzung und CO2-Gaswechsel bei der Blaualge Anacystis nidulans

Summary Changes in culture conditions caused strong changes in the pigment composition in the blue-green alga Anacystis nidulans. Under normal illumination (white light; 0.6·10³ erg/cm²·sec) the relation between the amounts of chlorophyll a and phycocyanin was 1:6.6. In a high light intensity (20.8·10³ erg/cm²·sec) the phycocyanin content was reduced and the relations thus changed to 1:1.9. Growing the algae in red light of high intensity (20·10³ erg/cm²·sec) increased the phycocyanin content; the chlorophyll a: phycocyanin relation was then 1:12.1.The action spectrum of apparent photosynthesis showed a minimum at 473 nm in all three cultures. The maximum of photosynthesis in low light cultures fell in the absorption region of phycocyanin at 621 nm. The action spectrum of the red light culture showed a reduced rate of photosynthesis in the same region. The strong light culture had an action spectrum similar to that of the red light culture with a maximum at 651 nm. The differing action spectrum of the low light culture may be a result of interruption in the energy transfer from phycocyanin to chlorophyll a within pigment system II.The transients of CO₂ exchange are independent of the pigment composition. Two different types of transients were found depending on the wavelength of the incident light. In red light of 550–650 nm a higher stationary rate was reached after a maximum of photosynthesis at the beginning of the illumination period. In blue and far red light a lower rate was found after the first maximum. Following a illumination period in blue or far red light a CO₂ evolution in the dark was observed. On the other hand, this CO₂ evolution was not found after illumination with red light. These effects are possiblt caused by a decarboxylation reaction (photorespiration) which occurs only in blue and far red light.     

Photosynthetische carboxylierungsreaktionen verschieden pigmentierter Anacystis-zellen

Summary CO₂ exchange, ¹⁴CO₂ fixation and ¹⁴C-labelled photosynthetic products of differently pigmented Anacystis nidulans (strain L 1402-1) were studied during the induction period at +30°C. The algae were grown at +35° C in an atmosphere of 0.04 vol.-% CO₂ and measured under the same low CO₂ concentrations. Changing the culture conditions caused alterations in the pigment composition. Under normal illumination (white light; 0.6×10³ erg/ cm² s) the relation between amounts of chlorophyll a and phycocyanin was 1:7 to 1:10. In a high light intensity (30.8×10³ erg/cm² s) the phycocyanin content was reduced (1:5 to 1:2). When the cells were grown in red light of high intensity (20×10³ erg/ cm² s) phycocyanin synthesis increased; the pigment ratio varied between 1:20 and 1:33. Anacystis cells grown under strong white light were filamentous.Photosynthetic CO₂ uptake, measured with an infrared gas analyzer, was very low in algae grown in high light intensity. The pattern of ¹⁴C-labelled photosynthetic products of these algae was very similar to those of the Calvin cycle. In Anacystis cells grown under low intensities of white light or in red light ¹⁴CO₂ was, at the beginning of the light period, incorporated mainly into aspatate and glycerine/serine. The enzyme activities of NAD⁺-specific malate dehydrogenase, ribulose-1,5-diphosphate carboxylase, aspartate and alanine aminotransferase decreased with increasing phycocyanin content. NADP⁺-specific malic enzyme activities showed practically no change. In contrast, phosphoenolpyruvate carboxylase activity increased with a higher rate of phycocyanin synthesis. In another series of experiments the behaviour of the PEP carboxylase activity after breakdown of the Anacystis cells was tested in differently pigmented cultures. In all cases the enzyme activities very rapidly decreased within two hours. The results obtained are discussed with reference to the correlation of pigment composition and CO₂ fixation of the phosphoenolpyruvate system.

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Abkürzungen Asp Aspartat - Gly/Ser Glycin/Serin - PGS 3-Phosphoglycerat - ZmP Zuckermonophosphat Herrn Professor Dr. Andre Pirson in Verehrung gewidmet     

Optical characteristics of a gallium laser plasma

Results are presented from studies of the emission from an erosion gallium laser plasma at a moderate intensity (W=(1–5)×10⁸ W/cm²) of a 1.06-μm laser radiation. It is shown that, under these conditions, the lower excited states of gallium atoms are populated most efficiently. Among the ions, only the most intense GaII lines are observed in the emission spectrum. The populations of GaI and GaII excited states are not related to direct electron excitation, but are determined by the recombination of gallium ions with slow electrons. The recombination times of GaIII and GaII ions in the core of the plasma jet are determined from the waveforms of emission in the GaII and GaI spectral lines and are equal to 10 and 140 ns, respectively. The results obtained are of interest for spectroscopic diagnostics of an erosion plasma produced from gallium-containing layered crystals during the laser deposition of thin films. __________ Translated from Fizika Plazmy, Vol. 27, No. 1, 2001, pp. 85–88. Original Russian Text Copyright ? 2001 by Shuaibov, Shimon, Dashchenko, Shevera, Chuchman.     

Factors influencing hydroxylamine inactivation of photosynthetic water oxidation

The kinetics of Mn release during NH₂OH inactivation of the water oxidizing reaction is largely insensitive to the S-state present during addition of NH₂OH. This appears to reflect reduction by NH₂OH of higher S-states to a common more reduced state (S₀ or S_?1) which alone is susceptible to NH₂OH inactivation. Sequences of saturating flashes with dark intervals in the range 0.2–5 s^?1 effectively prevent NH₂OH inactivation and the associated liberation of manganese. This light-induced protection disappears rapidly when the dark interval is longer than about 5 s. Under continuous illumination, protection against NH₂OH inactivation is maximally effective at intensities in the range 10³–10⁴ erg · cm^?2 · s^?1. This behavior differs from that of NH₂OH-induced Mn release, which is strongly inhibited at all intensities greater than 10³ erg · cm^?2 · s^?1. This indicates that two distinct processes are responsible for inactivation of water oxidation at high and low intensities. Higher S-states appear to be immune to the reaction by which NH₂OH liberates manganese, although the overall process of water oxidation is inactivated by NH₂OH in the presence of intense light. The light-induced protection phenomenon is abolished by 50 μM DCMU, but not by high concentrations of carbonyl cyanide m-chlorophenylhydrazone, which accelerates inactivation reactions of the water-splitting enzyme, Y (an ADRY reagent). The latter compound accelerates both inactivation of water oxidation and manganese extraction in the dark.     

Changes in Chlorophyll a/b Ratio and Products of CO(2) Fixation by Algae Grown in Blue or Red Light

Chlamydomonas and Chlorella were grown for 10 days in white light. 955 μw/cm² blue light (400-500 mμ) or 685 μw/cm² red light (above 600 mμ). Rates of growth in blue or red light were initially slow, but increased over a period of 5 days until normal growth rates were reestablished. During this adaptation period in blue light, total chlorophyll per volume of algae increased 20% while the chlorophyll a/b ratio decreased. In red light no change was observed in the total amount of chlorophyll or in the chlorophyll a/b ratio. After adaptation to growth in blue light and upon exposure to ¹⁴CO₂ with either blue or white light for 3 to 10 minutes, 30 to 36% of the total soluble fixed ¹⁴C accumulated in glycolate-¹⁴C which was the major product. However, with 1 minute experiments, it was shown that phosphate esters of the photosynthetic carbon cycle were labeled before the glycolate. Glycolate accumulation by algae grown in blue light occurred even at low light intensity. After growth of the algae in red light, ¹⁴C accumulated in malate, aspartate, glutamate and alanine, whereas glycolate contained less than 3% of the soluble ¹⁴C fraction.     

Polarization-Dependent Evanescent Optical Field Interaction with Atom and Its Effect on Atomic Emission Spectra

In this report, we present experimental results on evanescent optical field (EOF) interaction with ⁸⁵Rb vapor atoms. A circularly polarized EOF, 780 nm in wavelength, optically pumps the ⁸⁵Rb atoms from its upper ground state to its D2 excited state. A probe beam connecting the lower ground state of D2 transition stimulates emission of radiation from the excited atoms, which indicates additional atomic population excited by the circularly polarized EOF. Theoretical analysis and experimental results indicate that the circularly polarized EOF excites the D2 transition from ⁸⁵Rb(5²S_1/2, F?=?3, m _F ?=?±1) ground state to excited state (5²P_3/2, F’?=?3, m _F ?=?0) that creates an additional population to this state, which can be detected with the help of a probe laser beam.     

Physiological Characteristics of Photosynthesis and Respiration in Stems of Populus tremuloides Michx

The physiological responses of 6- to 8-year-old aspen (Populus tremuloides Michx.) stems to temperature, light, and CO₂ concentration were investigated in the field throughout the year using infrared CO₂ analysis. Light response studies showed that the rate of gross photosynthesis was linear from 0 to 400 ft-c (0 to 1.6 mw/cm² of 400-700 nm) with light saturation being reached between 800 to 1400 ft-c (3.2 to 5.6 mw/cm² of 400-700 nm). At this light intensity, the respiratory CO₂ loss was reduced to 10 to 15% of dark rates. Net photosynthetic CO₂ uptake was not observed even at intensities as high as 3400 ft-c (13.6 mw/cm² of 400-700 nm). The light response curve was similar for both winter and summer stems.     

White light requirements for stimulation of plant growth by malformin

Over a 3-day period, the minimum white fluorescent light intensity required for malformin-induced growth stimulation of etiolated and green cuttings of Phaseolus aureus was approximately 2.6 × 10³ and 0.4 × 10³ ergs/cm² · sec, respectively. High light intensities were unable to inhibit the ability of malformin to stimulate growth. Over 3 days, the minimum photoperiod for malformin-induced growth stimulation using etiolated and green cuttings and a light intensity of 13.5 × 10³ ergs/cm² · sec was 4 hours and 1 hour, respectively. Malformin must be present in the area of growth stimulation during the time of light treatment. Those changes induced by light and required for malformin-induced growth stimulation were estimated to undergo almost complete decay within 1 hour in the dark. By manipulating the experimental technique, it was possible to stimulate the growth of green cuttings with malformin with a 10-min light treatment (13.5 × 10³ ergs/cm² · sec). Although low light intensities and short photoperiods did not allow growth stimulation by malformin using etiolated cuttings, they prevented or alleviated growth inhibition induced by malformin in the dark.     

Eine fördernde Wirkung von Blaulicht auf die Carotinoidbildung einer gelben Chlorella-Mutante

Summary In growing as well as in resting cells of a chlorophyll-free yellow mutant of Chlorella vulgaris (211-11h/20) synthesis of carotenoids is enhanced by blue light. Permanent irradiation is necessary to maintain the effect (Fig. 2). At wavelengths around 454 nm the additional carotenoid production is half-saturated at about 1000 erg cm^-2s^-1 and saturated at about 4000 erg cm^-2s^-1 (Fig. 3). An action spectrum exhibits highest efficiency of wavelengths around 465 and 370 nm, a minimum near 400 nm and inefficacy of yellow, red and far-red light (Fig. 4). This wavelength dependence resembles those of light enhanced O₂-uptake, carbohydrate consumption and gain of organically bound nitrogen by the organism.     

Effects of Quality, Intensity, and Duration of Light Breaks during a Long Night on Dormancy in Blue Spruce (Picea pungens Engelm.) Seedlings

Blue spruce (Picea pungens Engelm.) seedlings grow continuously when exposed to photoperiods exceeding 16 hours and enter dormancy within 4 weeks under photoperiods of 12 hours or less. Dormancy was prevented under 12-hour photoperiods by 2-hour light breaks of red light (1.70 μw/cm² at 650 nm) or high intensity white light (2,164.29 μw/cm² at 400 to 800 nm) given in the middle of the 12-hour night, and by continuous low intensity white light (204.76 μw/cm² at 400 to 800 nm). Two-hour light breaks of far red light (1.80 μw/cm² at 730 nm), red light followed by far red light, or low intensity white light were not effective in delaying dormancy. The results imply that the phytochrome system mediates the photoperiodic control of dormancy in blue spruce seedlings. The similarity of results obtained using the low intensity, long duration as against the high intensity, short duration light treatments suggests that the law of reciprocity applies in this response.     

The effects of light intensity and spectral quality on growth and shoot initiation in tobacco callus

The effects of eight different narrow band-emitting fluorescent lamps (371-750 nm) and four commercial broad band-emitting fluorescent sources upon growth and shoot initiation in tobacco callus (Nicotiana tabacum var. Wisconsin 38) have been characterized. Wavelength and intensity are equally important parameters in determining morphogenic changes. Near ultraviolet light (371 nm) was found to stimulate (0.024 mw/cm²) or inhibit (above 0.15 mw/cm²) callus growth and shoot initiation, depending on the light intensity. Stimulation of growth and shoot production occurs also in blue light region, but at higher intensity than in the near ultraviolet. Red and far red light (up to 1.7 mw/cm²) do not appear to affect callus growth or stimulate shoot initiation. The enhancement of callus growth and the stimulation of shoot initiation are controlled by the same near ultraviolet-absorbing photoreceptor system present in a small enough concentration that it cannot be recognized in the absorption spectrum of the intact tissue. Carotenoids, porphyrins, and phytochrome associated with the high irradiance response do not appear to qualify as the photoreceptor. Flavonoids are possible candidates. Radiation emitted by fluorescent lamps outside the near visible region was determined, and we concluded that energy levels were not sufficient to affect the reported results. The spectral output of several commercial lamps in the visible and near visible regions is such that there could be different effects on growth and development of tissue cultures.     

The survival of amphibian embryos after continuous ultrasonic treatment

The effect of continuous ultrasonic treatment on the development of early embryos of common frog Rana temporaria was studied. Intact embryos at the blastula stage were exposed to ultrasound of various frequencies (0.88 and 2.64 MHz) and intensities (0.05 to 1.0 W/cm²) for various periods (1 to 15 min). The increase in ultrasound intensity to 0.7–1.0 W/cm² and exposure time to 5–15 min resulted in nearly complete mortality. Development of the embryos exposed to ultrasound of medium intensity (0.2–0.7 W/cm²) for 1–5 min was virtually similar to the control. Treatment at a frequency of 2.64 MHz and intensity of 0.05–0.7 W/cm² for 1–5 min had no effect on the development of amphibian embryos and their survival rate. The increase in intensity of the ultrasound of this frequency to 1 W/cm² and the exposure time to 5 min decreased the number of normally developing embryos by 35%.     

Light and calcium interactions in chlorella inhibited by sodium chloride

Analysis of NaCl toxicity in Chlorella sorokiniana showed decreased growth rates, increased dry weight per cell, increased intracellular Na⁺ and Cl⁻, more total chlorophyll per cell, a decreased chlorophyll a to chlorophyll b ratio, increased rates of O₂ evolution, and decreased rates of CO₂ fixation when the extracellular concentration of NaCl was increased from zero to 0.3 m. Cultures did not grow at concentrations greater than 0.3 m NaCl unless 10 mm calcium salts were present. Inclusion of that concentration of Ca²⁺ extended the tolerance to 0.5 m NaCl before growth stopped. Increasing the light intensity from 1.2 to 9.4 mw/cm² increased growth rates for cultures in 0.10 to 0.45 m NaCl. At 14 mw/cm² added Ca²⁺ reduced growth rates of cultures in 0.3 m NaCl compared to controls without added Ca²⁺. Maximal growth rates for cultures in NaCl media were achieved by addition of 10 mm CaSO₄ and maintenance of the light intensity at 9.4 mw/cm². The maximal growth rate of the organism was 9.6 doublings/day achieved at 2.7 mw/cm² for control cultures. In 0.3 m NaCl the growth rate was 4.3 doublings/day at 2.7 mw/cm² and 8.2 doublings/day at 9.4 mw/cm² with 10 mm CaSO₄ added.     

Evidence for the role of light intensity in the seasonal testicular cycle of a wild bird,black headed munia

Abstract

The effects of various light intensity levels (0.11, 0.48, 0.96 and 1.86 mW/cm²) of constant white light on the testicular cycle of a wild bird, Black headed munia were investigated. While in higher intensity (0.96 and 1.86 mW/cm²) treated birds precocious gonadal development was observed, low intensity illumination prevented gonadal regression, indicating a better maintenance of testicular activity under low intensity lighting in Black headed munia. Since the total hours of light exposure (24 hr/day) were the same for all the four experimental groups, and higher intensities could not prevent gonadal regression, it would seem that light intensity is more important than the hours of illumination in the reproduction of this bird.     

Regulation of CO2-fixation in Chlorella by light of varied wavelengths and intensities

1) The wavelength effects on ¹⁴CO₂-fixation by Chlorella cellswere studied, using monochromatic light of different light intensities. 2) Blue light (453 mµ) stimulated the incorporation of¹⁴C into aspartate, glutamate and malate. Red light (679 mµ),on the other hand, stimulated its incorporation into P-esters,free sugars and insoluble material. 3) The blue light effect was observed in the presence of CMUat concentrations completely suppressing ordinary photosyntheticCO₂-fixation. 4) The blue light effect in the presence of CMU was inducedat very low intensities. At 453 mµ, 300 erg cm^–2sec^–1 was sufficient for complete saturation. 5) Time courses of ¹⁴C-incorporation into individual compoundswere investigated. Irrespective of the wavelength of the illuminatinglight, the first stable CO₂-fixation product formed under weaklight (400–500 erg cm^–2 sec^–1) was citrulline.At higher light intensities (4,000–7,000 erg cm^–2sec^–1), PGA was the first stable CO₂-fixation product.The incorporation of ¹⁴C into citrulline was not inhibited byCMU. 6) Experimental results indicate that both blue light-inducedincorporation of ¹⁴C into amino and organic acids and the incorporationof ¹⁴C into citrulline induced by low intensity light are operatedby a mechanism(s) independent of ordinary photosynthetic CO₂-fixation.Possible effects of light regulating the carbon metabolism inalgal cells are discussed. (Received July 24, 1969; )     

Effect of zooplankton availability on the rates of photosynthesis, and tissue and skeletal growth in the scleractinian coral Stylophora pistillata

This work investigated the effect of light and feeding on tissue composition as well as on rates of photosynthesis and calcification in the zooxanthellae (zoox) scleractinian coral, Stylophora pistillata. Microcolonies were maintained at three different light levels (80, 200, 300 μmol m⁻² s⁻¹) and subjected to two feeding regimes (starved and fed) over 9 weeks. Corals were fed both natural plankton and Artemia salina nauplii four times a weeks and samplings were made after 2, 5, and 9 weeks. Results confirmed that feeding enhances coral growth rate and increases both the dark and light calcification rates. These rates were 50-75% higher in fed corals (FC; 60±20 and 200±40 nmol Ca²⁺ cm⁻² h⁻¹ for dark and light calcification, respectively) compared to control corals (CC; 30±9 and 124±23 nmol Ca²⁺ cm⁻² h⁻¹). The dark calcification rates, however, were four times lower than the rates of light calcification (independent of trophic status). After 5 weeks, chlorophyll a (chl-a) concentrations were four to seven times higher in fed corals (7-21 μg cm⁻²) than in control corals (2-5 μg cm⁻²). The amount of protein was also significantly higher in fed corals (2.11-2.50 mg cm⁻²) than in control corals (1.08-1.52 mg cm⁻²). Rates of photosynthesis in fed corals were 2-10 times higher (1.24±0.75 μmol O₂ h⁻¹ cm⁻²) than those measured in control corals (0.20±0.08 μmol O₂ h⁻¹ cm⁻²).     

Effects of ultraviolet radiation on carotenoid-containing and albino strains of Neurospora crassa

To determine the influence of carotenoids on UV sensitivity of Neurospora crassa conidia, the dose-response curves of 3 albino strains were compared to that of the wild type. In a control experiment the genetic background effects were eliminated by irradiating the wild type in which carotenoid synthesis had been inhibited by β-ionone, and comparing the dose-response curve to that of untreated wild type. All strains used had similar γ-ray survival curves and nuclei per conidium which precluded differences in UV sensitivity due to morphological differences.The albinos and β-ionone-treated strains showed a greater sensitivity (mean LD50 4.35·10³ erg/mm²) to UV irradiation than the wild type (LD50 7.30·10³ erg/mm²).