Effects of light intensity on the growth rate of the red alga Porphyridium cruentum

The red alga, Porphyridium cruentum, which is one of the potential sources of arachidonic acid, was cultured in batch and continuous vessels. The growth rates in batch cultures were correlated to the mean light intensity in the vessels, and the cell concentrations in continuous cultures were estimated by those results. The yield of arachidonic acid was about 1.2 g per 10¹² cell at cell concentrations ranging from 0.5 to 1.5 × 10¹⁰ cell/l and independent of the mean light intensity.     

Light-induced Adhesion of Spirogyra Cells to Glass

Adhesion of Spirogyra (tentatively, Spirogyra fluviatilis) cells to glass is described. The cells of an algal filament can adhere to a substrate only when they are located at the end of the filament. Rapid adhesion is induced by blue-violet light (blue adhesion) as well as by temperature shift (about 6 C → about 22 C) or shaking (dark adhesion). Adherent cells detach in 1 hour in the absence of one of these stimuli. Slow adhesion is induced by red light (red adhesion) 1 hour after irradiation, and may be controlled by phytochrome. A cell once caused to adhere by red light does not release from the glass.     

Wirkungsspektren der Anthocyansynthese in Gewebekulturen und Keimlingen von Haplopappus gracilis

Summary The biosynthesis of anthocyanin in tissue cultures and intact seedlings of Haplopappus gracilis is a light-dependent reaction which can be induced by blue light only. Anthocyanin appeared in all organs of the seedling.Wounding of the plant led to an increase in the content of anthocyanin due to increased anthocyanin synthesis in the cotyledons.The action spectra of anthocyanin formation in tissue cultures and intact seedlings have two peaks, one at 438 nm and the other at 372 nm. The limit of activity in the direction of longer wavelengths lies between 474 and 493 nm. Red light of short and long wavelength is ineffective in the induction of pigment synthesis. The photoreceptor of the light reaction is supposed to be a yellow pigment (flavoprotein or carotinoid). In contrast to the intact plants, isolated cotyledons and wounded seedlings are able to form anthocyanin not only in the blue region but also during irradiation with red light of high intensity. The action spectrum of anthocyanin synthesis in the isolated cotyledons has a marked maximum at about 440 nm and a second one at about 660 nm. A little activity can be observed throughout the visible spectrum. The pigment synthesis induced by red light can be completely suppressed by DCMU, an inhibitor of photosynthesis. This indicates that in the case of the activity in the red light caused by wounding chlorophyll serves as photoreceptor.The anthocyanin synthesis in tissue cultures and seedlings could not be influenced by low energy radiation in the red or in the far red region, even after induction of anthocyanin synthesis by blue light of high intensity. Therefore it seems that the phytochrome system is not involved in anthocyanin synthesis in Haplopappus gracilis.     

The effect of red and far red light on the desaturation of Fatty acids in barley leaves

Barley (Hordeum vulgare) leaf tissue was either (a) exposed to continuous red light or (b) exposed to red, far red, or red followed by far red light. The fatty acid composition and incorporation of acetate-2-¹⁴C into linolenate were determined. Changes occurred in the fatty acid composition of dark-grown barley leaves regardless of whether the plants were subsequently exposed to red light or whether the tissue remained in the dark. Measurements were also made of the fatty acids of the coleoptile. Red light treatment did not reduce the lag period for the synthesis of linolenate when chlorophyll synthesis was inhibited. It appears that the desaturation process per se in the synthesis of linolenate is not phytochrome-mediated but may appear to be phytochrome mediated if, possibly, galactolipid and chlorophyll syntheses occur concomitantly.     

Characterization of the light reaction in promoting the mobilizing ability of rose shoot tips

Mixed fluorescent and incandescent light increased growth and sink strength of the uppermost young shoot of rose plants (Rosa hybrida cv. Marimba) in comparison to pure fluorescent light. This was manifested by increased apical dominance. Monochromatic low-energy red light, given by means of optic fibers for 24 hours to shoot tips that had been previously darkened for 5 days, increased the transport of ¹⁴C-labeled assimilates to the intact tips and the uptake of [¹⁴C]sucrose by detached tips. Far-red had little or no effect, and blue was not effective at all in these reactions. Red light given directly to detached shoot tips, in vitro, increased the uptake of [¹⁴C]sucrose by the isolated tips. Adding far-red to the red greatly promoted the uptake, whereas blue and blue plus far-red were not active. The main character of the light reaction promoting sink activity in the shoot is that it is perceived by the shoot tip itself. It is operated by red light; far-red promotes the red effect but has little or no effect when alone. Light apparently promotes shoot sink activity by increasing the unloading process.     

The regulation of synthesis of mitochondrial enzymes in regreening and division-synchronized Euglena cultures

The effect of light and carbon nutrition on the synthesis of citrate synthase (EC 4.1.3.7) and malate dehydrogenase (EC 1.1.1.37) in dark-grown resting (carbon deficient) and in phototrophic division-synchronized cultures of Euglena gracilis Klebs strain z were investigated. Exposure of dark-grown Euglena to white or red light produced a transient increase in the specific activities of citrate synthase and malate dehydrogenase but blue light (of equal energy) was ineffective. Citrate-synthase activity increased at the end of the light phase and in early dark phase in phototrophic cultures division-synchronized by a regime of 14 h light-10 h dark. The addition of ethanol or malate produced a twofold increase in citrate-synthase activity compared with phototrophic cultures. White and blue light, but not red light, produced a transient repression of the metabolite-induced increase in citrate-synthase activity in division-synchronized cultures. Since only red light could effect a transient increase in the specific activity of mitochondrial enzymes, and the blue-red plastid receptor should respond to both blue and red light, the synthesis of mitochondrial enzymes in regreening cultures may be under the control of a new photoreceptor responding only to red light. In division-synchronized phototrophic cells the primary effector of synthesis of mitochondrial enzymes is not light but carbon nutrition.     

Light requirements for regeneration of protoplasts of the moss Physcomitrella patens

Protoplasts prepared by enzymic treatment of protonemata of the moss Physcomitrella patens regenerate rapidly in white light (15 W m^?2). The great majority of protoplasts follow a simple regenerative sequence, namely: cell wall synthesis; formation of an asymmetric cell; division of the asymmetric cell, and further extension and division to produce a new chloronemal filament. Only cell wall formation occurs independently of light. The production of an asymmetric cell requires relatively high photon fluence rates of blue or red light and ceases upon transfer to darkness. The subsequent stages of regeneration require much lower photon fluence rates, and red light is considerably more effective than blue or far-red light in permitting cell division. This system is of interest in the study of the induction of cell polarity in plants.     

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.     

Phytochrome-mediated de Novo Synthesis of Phenylalanine Ammonia-Lyase in Cell Suspension Cultures of Parsley

After a preirradiation with ultraviolet light, phenylalanine ammonia-lyase activity in cell suspension cultures of parsley (Petroselinum hortense Hoff.) is controlled by phytochrome (red/far red photoreversibility). Isopycnic CsCl density gradient centrifugation, after labeling with ¹⁵N (90 atom%) under inductive and noninductive conditions, was used to investigate the mode of action of phytochrome in this response. After a 5hour labeling period, a buoyant density shift of 0.009 kg·l⁻¹ (0.7%) without band-broadening (indicating close to maximal labeling of the enzyme), was observed in irradiated cells. In dark-grown controls, the density shift was 0.004 kg·l⁻¹ (0.3%), accompanied by significant band-broadening, indicating turnover of about half of the enzyme pool during 5 hours. These results are taken as evidence that phytochrome controls de novo synthesis of this enzyme over a background of basal turnover.     

Effect of light and natural ventilation systems on the growth parameters and carvacrol content in the in vitro cultures of <Emphasis Type="Italic">Plectranthus amboinicus</Emphasis> (Lour.) Spreng

The aim of the current study is to investigate the influence of light intensity, quality of light and alternative membrane sytems on the growth and headspace-GC/MS chemical analysis of Plectranthus amboinicus cultivated in vitro. Nodal segments were grown under light intensities (26, 51, 69, 94 and 130 µmol m^?2 s^?1) provided by cool-white fluorescent lamps. Apical segments were grown under light-emitting diodes blue; red; 1 blue/2.5 red; 2.5 blue/1 red; 1 blue/1 red and white fluorescent lamps. Apical and nodal segments were grown under alternative membrane and membrane-free systems. One, two or four PTFE membranes were used on the lid of the culture vessel. The membranes provided natural ventilation and worked as filters. The results have shown significant differences in the growth and carvacrol content, as well as in the content of carvacrol precursors (γ-terpinene and p-cymene) in different treatments. Among all tested light intensities, the significant increase in the dry weight and in the carvacrol content of plantlets derived from the nodal segments was recorded at 69 µmol m^?2 s^?1. The monochromatic red led to greater shoot length and higher dry weight in plantlets derived from the apical segments, as well as to carvacrol accumulation greater than that provided by the fluorescent lamps. The culture vessel enclosure by one and two membranes led to higher dry weight in plantlets derived from the apical and nodal segments, respectively. They also showed higher carvacrol content. Thus, it is possible optimizing the growth and carvacrol content in P. amboinicus cultivated in vitro by adjusting these environmental parameters.     

Induction mechanism of adventitious root from leaf explants of <Emphasis Type="Italic">Morinda citrifolia</Emphasis> as affected by auxin and light quality

An efficient protocol for adventitious root induction from leaf explants of Morinda citrifolia treated with different concentrations of indole-3-butyric acid (IBA) and α-naphthaleneacetic acid (NAA) was established in relation to physiological process changes during adventitious root induction under different light sources (fluorescent, red, blue, red + blue, and far-red). Among the different concentrations of IBA and NAA, 1.0 mg l⁻¹ IBA was proven as the best auxin source for adventitious root induction under fluorescent light. Higher concentrations of IBA and NAA trigger callus formation in both light and dark conditions. Maximum numbers of adventitious roots were induced under red light (26) followed by blue light (22) and the lowest under far-red light (6). In contrast, numerous callus formations were induced by red + blue followed by red and blue, while the highest root length (1.66 cm) with negligible callusing was observed under fluorescent light. Catalase and guaicacol peroxidase activities were highest under red light followed by fluorescent light and the lowest under red + blue light, but superoxide dismutase activity was not significantly influenced by different light sources. Ascorbate peroxidase played an important role in detoxification of the harmful effects of hydrogen peroxide (H₂O₂). Under fluorescent light, significantly lower accumulation of H₂O₂ was observed. Accumulation of H₂O₂ in the induced root under different light showed a positive correlation with peroxidation of lipids and was observed higher under far-red followed by red + blue and blue light.     

Photobiology of diagravitropic maize roots

Light-induced modification of gravitropism in etiolated roots of Zea mays cv Bear × W38 is a low fluence response mediated by phytochrome. This cultivar has a threshold of 10⁻⁶ mol m⁻² and becomes saturated with 10⁻² mol m⁻² of red light. The maximum light-mediated response of 32 degrees downward from horizontal occurs in roots 10 to 30 millimeters in length, 120 to 165 minutes after irradiation. Reciprocity is valid from 2 to at least 9,000 seconds and the response can be about 90% reversed by far red light. Photoreversibility is lost (`escape' occurs) about 20 minutes after red irradiation but appears to be regained 60 to 80 minutes later. A red light-induced (or synchronized) nutation in the apparent curvature rather than unusual escape characteristics may explain these results.     

Production of bioactive phenolic acids and furanocoumarins in in vitro cultures of Ruta graveolens L. and Ruta graveolens ssp. divaricata (Tenore) Gams. under different light conditions

Extracts from the biomass of Ruta graveolens and Ruta graveolens ssp. divaricata cultured in vitro under different light conditions (far-red, red and blue light, UV-A irradiation, in darkness and white light) were tested for the amounts of free phenolic acids and cinnamic acid (twelve compounds) as well as furanocoumarins and umbelliferone (seven compounds) using HPLC methods. Total amounts of the investigated groups of compounds in the cultures of both plants increased from 2.6 to 6.7 times, depending on light quality, and the maximum values reached were 106.50 and 1,276.74?mg?100?g^?1 DW (in R. graveolens), and 106.97 and 262.54?mg?100?g^?1 DW (in the subspecies), respectively. Both white light and blue light were equally beneficial for the total production of phenolic acids in cultures of both plants, whereas the total production of furanocoumarins was clearly better stimulated by blue light in R. graveolens and by darkness in the subspecies (i.e. the amounts were respectively 1.44 and 1.7 times higher than in the biomass cultivated under white light). The amounts of individual compounds in both plant cultures increased from about 2.2 to 26.3 times depending on light quality. The following bioactive compounds were obtained in quantities which are of interest from a practical perspective: in R. graveolens culture??protocatechuic acid (45?mg?100?g^?1 DW), isopimpinellin (about 500?mg?100?g^?1 DW) and bergapten (about 270?mg?100?g^?1 DW), and in the subspecies culture: p-coumaric acid (70?mg?100?g^?1 DW) and isopimpinellin (about 210?mg?100?g^?1 DW).     

Effects of Light on the Membrane Potential of Protoplasts from Samanea saman Pulvini : Involvement of K Channels and the H -ATPase

Rhythmic light-sensitive movements of the leaflets of Samanea saman depend upon ion fluxes across the plasma membrane of extensor and flexor cells in opposing regions of the leaf-movement organ (pulvinus). We have isolated protoplasts from the extensor and flexor regions of S. saman pulvini and have examined the effects of brief 30-second exposures to white, blue, or red light on the relative membrane potential using the fluorescent dye, 3,3′-dipropylthiadicarbocyanine iodide. White and blue light induced transient membrane hyperpolarization of both extensor and flexor protoplasts; red light had no effect. Following white or blue light-induced hyperpolarization, the addition of 200 millimolar K⁺ resulted in a rapid depolarization of extensor, but not of flexor protoplasts. In contrast, addition of K⁺ following red light or in darkness resulted in a rapid depolarization of flexor, but not of extensor protoplasts. In both flexor and extensor protoplasts, depolarization was completely inhibited by tetraethylammonium, implicating channel-mediated movement of K⁺ ions. These results suggest that K⁺ channels are closed in extensor plasma membranes and open in flexor plasma membranes in darkness and that white and blue light, but not red light, close the channels in flexor plasma membranes and open them in extensor plasma membranes. Vanadate treatment inhibited hyperpolarization in response to blue or white light, but did not affect K⁺ -induced depolarization. This suggests that white or blue light-induced hyperpolarization results from activation of the H⁺ -ATPase, but this hyperpolarization is not the sole factor controlling the opening of K⁺ channels.     

Enhancement of phycobiliprotein production in nitrogen-fixing cyanobacteria

The influence of several environmental factors on the phycobiliprotein content of two phycoerythrin-rich nitrogen-fixing cyanobacteria has been studied in order to maximize pigment production. Total phycobiliprotein content was enhanced when either temperature within the optimum range for growth or cell density of the culture was increased. The phycobiliprotein level increased also in response to a decrease in irradiance. In all cases the effect was more marked for C-phycoerythrin than for C-phycocyanin and allophycocyanin. The cellular content in C-phycoerythrin was also preferentially enhanced when cultures were irradiated with green light. On the other hand, red light induced an increase in the C-phycocyanin content, but the C-phycoerythrin level decreased considerably.     

An investigation of the effects of light on basidiocarp formation of Coprinus domesticus

Coprinus domesticus, grown on a synthetic agar medium, failed to produce primordia and basidiocarps unless exposed to light. Lightdark cycles are not required for maturation of basidiocarps. Short exposure to white light induced primordia, but a longer exposure was necessary for primordia to develop into basidiocarps. The length of exposure to light was related inversely to the length the stipe finally attained. Young basidiocarps were phototropic, growing towards the light. The mycelium of cultures were dark brown following exposure to white and blue light, but the mycelium was light yellow in cultures grown in darkness. The blue end of the visible spectrum at intensities ranging from 1.5–3 × 10⁴ ergs/cm²/sec induced mature basidiocarps, whereas green, red and far red failed to induce basidiocarps and primordia.Department of Biology contribution no. 90