Measurement of Light Absorption and Determination of the Specific Rate of Light Uptake in Cultures of Phototrophic Microorganisms

This article describes a novel method for the measurement of light absorption by cultures of phototrophic microorganisms. The rate of light absorption is calculated as the difference between the rate of light output from a culture containing cells and the rate of light output from a culture containing only growth medium. The specific rate of light uptake is calculated by dividing the rate of light absorption by the total biomass present in the culture. Application of the method to several case studies shows that light output from a culture varies widely depending on the absorption and scattering characteristics of the suspension.     

Barley Leaf Unfolding under Mixtures of Red and Blue Light

Barley leaf unfolding is stimulated by mixed red and blue light. However, the stimulation from mixed light is attenuated when compared with the stimulation from red light alone, particularly for low intensities of the mixed light and for short irradiation times. For higher light intensity mixtures of red and blue light and for longer irradiation times, the blue light enhances the stimulation from red light and vice versa. This supports the assumption that the blue light effect in this case is also mediated by the phytochrome system. Furthermore the present findings point to the possibility of competitive reactions caused by red and blue light in the excitation of phytochrome.     

Photocontrol of in vitro bud differentiation in Saintpaulia ionantha leaves and Lycopersicon esculentum cotyledons

The regeneration of buds from leaves of Saintpaulia ionantha Wendl cv. Sona and from cotyledons of Lycopersicon esculentum Mill. cv. UC 105 was studied in response to continuous light and daily light pulses. The regeneration of buds from cotyledons of Lycopersicon esculentum is high under continuous red and white light. Trie effect of light may be related to phytochrome. In Saintpaulia ionantha blue light appears to be very effective. The experimental results suggest that the blue light effects involve both a blue light absorbing photoreceptor and phytochrome     

The effects of continuous light and light intensity on the reproduction rates of twenty-two species of marine phytoplankton

The acclimated reproduction rates of 22 species of marine phytoplankton were measured at 0.01, 0.023, 0.1, and 0.23 ly/min in continuous light and in a 14: 10 h light: dark cycle. Three species that reproduced exponentially at all four light intensities in the 14: 10 LD regime did not reproduce at all in continuous light at any of the light intensities. One species, which reproduced at the two lowest light intensities in the 14: 10 LD regime, failed to reproduce at all in continuous light at any light intensity examined. Seven species reproduced more slowly in continuous light than in the 14: 10 LD regime at most or all light intensities. Four species reproduced at roughly the same rate in both light regimes. Five species reproduced more rapidly in continuous light.

No general phylogenetic trend could be discerned from the responses of the species to the different light intensities or to continuous light. In general, species from coastal regions can reproduce as rapidly or more rapidly in continuous light than in a 14: 10 LD cycle, while most species from oceanic regions are harmed by continuous light. A phylogenetic trend in maximum potential reproduction rate is apparent, with diatoms being the fastest, dinoflagellates the slowest, and coccolithophores somewhat intermediate.     

Characteristics of iron release from isolated heavy and light endosomes

1. Endosomes were isolated from K 562 cells after 3 min after the endocytosis of a single cohort of transferrin molecules. 2. The change in 125I/59Fe ratio of heavy and light endosomes, relative to that of the transferrin used and 59Fe from light endosomes. 3. Incubation of heavy and light endosomes with PBS or PIH showed equal ATP specific iron release from both heavy and light endosomes, but in the presence of a NADH/NAD+ redox couple iron release from light endosomes was reduced. 4. Incubation of heavy and light endosomes with PIH and NEM did not completely abolish ATP specific iron release from heavy and light endosomes.     

Effects of seed mass on seedling success in Artocarpus heterophyllus L., a tropical tree species of north-east India

I examined the effects of seed mass on performance of seedlings of Artocarpus heterophyllus L. (Moraceae), a large evergreen late successional shade-tolerant tree species in three contrasting light conditions. Seed mass varied many fold from 1.5 to 14 g in A. heterophyllus. Germination and germination time showed a significant correlation with seed mass. Germination differed significantly among three light regimes (50%, 25% and 3%). Seed mass and light level significantly affected seedling survival. The seedlings that emerged from large seeds survived better than those from small seeds under all light regimes. Survival of seedlings was maximum in 25% light regime for all seed mass classes but did not differ significantly from that at 50% light regime. Survival was significantly lower in 3% light as compared to 50% and 25% light regimes. Seedling vigor (expressed in terms of seedling height, leaf area and dry weight) was also significantly affected by seed mass and light regimes. Seedlings that emerged from larger seeds and grew under 50% light regime produced the heaviest seedlings, while those resulting from smaller seeds and grown under 3% light regime produced the lightest seedlings. Resprouting capacity of seedlings after clipping was significantly affected by seed mass and light regime. Seedlings emerging from larger seeds were capable of resprouting several times successively. Resprouting was more pronounced under 50% and 25% light regimes as compared to 3% light. Success of A. heterophyllus regeneration appears to be regulated by an interactive effect of seed mass and light regime.     

Relative effectiveness and interaction of ultraviolet-B, red and blue light in anthocyanin synthesis of apple fruit

The effect of light on anthocyanin production in apple ( Malus pumila Mill. cv. Jonathan) skin disks was investigated, with prolonged irradiation from different light sources. High fluence rates of white light provided from a xenon lamp were unable to produce large amounts of anthocyanin, and anthocyanin production became saturated at about 30 W m⁻². When UV-B light, provided by a fluorescent lamp which had an emission peak at 312 nm, was combined with the white light, anthocyanin production was synergistically stimulated and increased up to the highest fluence rates of white light tested (44 W m⁻²). This UV-B light was more effective than red and blue light provided from fluorescent lamps, but anthocyanin production became saturated at about 1.7 W m⁻². However, simultaneous irradiation with red and UV-B light had a synergistic effect. UV-B light was also effective in increasing anthocyanin production in whole fruit. Therefore this synergism seemed to have an important role in the development of the desirable red skin color under field light conditions. The results of aminoethoxyvinylglycine treatment suggested that ethylene was not involved in the stimulative effect of UV-B light.     

A parallel bubble column system for the cultivation of phototrophic microorganisms

An incubator with up to 16 parallel bubble columns was equipped with artificial light sources assuring a light supply with a homogenous light spectrum directly above the bioreactors. Cylindrical light reflecting tubes were positioned around every single bubble column to avoid light scattering effects and to redirect the light from the top onto the cylindrical outer glass surface of each bubble column. The light reflecting tubes were equipped with light intensity filters to control the total light intensity for every single photo-bioreactor. Parallel cultivations of the unicellular obligate phototrophic cyanobacterium, Synechococcus PCC7942, were studied under different constant light intensities ranging from 20 to 102 microE m(-2)s(-1) at a constant humidified air flow rate supplemented with CO(2).     

Branching responses of a plagiotropic clonal herb to localised incidence of light simulating that reflected from vegetation

Plants sense the presence of neighbouring vegetation through phytochrome photoreceptors perceiving a lowered red to far-red ratio (R:FR) of light reflected from such vegetation. We hypothesised that it would be advantageous for the grassland clonal herb, Trifolium repens, to have an inhibitory branching response to perception by leaves of light reflected from neighbouring vegetation (i.e. light with lowered R:FR ratio) but have no response to interception of such light by the plagiotropic stem. We tested whether photoreception of reflected light by plagiotropic stems resulted in a different branching response to photoreception by leaves and whether leaf ontogeny influenced the response. To simulate light reflected from vegetation, FR light-emitting-diodes were used to supplement controlled environment room light so that the R:FR ratio, but not the photosynthetic photon fluence rate, of light incident at the stem or leaf of a phytomer of T. repens was lowered from 1.20 to 0.25. The plagiotropic stems were unresponsive to light simulating that reflected from vegetation. This response differs from that of stems of orthotropic species, indicating that plagiotropic stems have evolved an organ-specific photobiology. Treatment of the mature leaf with light of lowered FR ratio reduced phytomer production only of the branch in the axil of the treated leaf. Similar treatment of the immature leaf retarded, in addition, branching at basal phytomers on the same side of the primary stem axis. Thus the response to light simulating that reflected from neighbouring vegetation depended upon whether the light was incident at the stem or the leaf and on the stage of leaf development. We argue that such responses improve the performance and fitness of T. repens within grassland habitats by allowing axillary buds on plagiotropic stems to branch freely when stems are in receipt of light reflected from vegetation while leaves are in full light.     

Relationship between light conditions and behavior of the freshwater snail Biomphalaria glabrata (Say)

The influence of light upon behavior of Biomphalaria glabrata was investigated in snails submitted for 48 h to one of the following regimes: normal light cycle, continuous darkness, continuous light. Time-lapse cinematography was used to provide data about snail locomotor activity in response to (a) continuous light or darkness; (b) light or dark phases; (c) light transitions. Snails were significantly less active under continuous light than under continuous or intermittent darkness. Under the normal light cycle, the activity rate was significantly higher in the dark than in the light. Changes from light to dark corresponded to increases in the activity rate which persisted long afterwards. No significant variation in activity occurred upon changes from dark to light.     

Reversal by green light of blue light-stimulated stomatal opening in intact, attached leaves of Arabidopsis operates only in the potassium-dependent, morning phase of movement

Green light reversal of blue light-stimulated stomatal opening was discovered in isolated stomata. The present study shows that the response also occurs in stomata from intact leaves. Arabidopsis thaliana plants were grown in a growth chamber under blue, red and green light. Removal of the green light opened the stomata and restoration of green light closed them to baseline values under experimental conditions that rule out a mesophyll-mediated effect. Assessment of the response to green light over a daily time course showed that the stomatal sensitivity to green light was observed only in the morning, which coincided with the use of potassium as a guard cell osmoticum. Sensitivity to green light was absent during the afternoon phase of stomatal movement, which was previously shown to be dominated by sucrose osmoregulation in Vicia faba. Hence, the shift away from potassium-based osmoregulation in guard cells is further postulated to entail a shift from blue light to photosynthesis as the primary component of the stomatal response to light. Stomata from intact leaves of the zeaxanthin-less, npq1 mutant of Arabidopsis failed to respond to the removal or restoration of green light in the growth chamber, or to short, high fluence pulses of blue or green light. These data confirm previous studies showing that npq1 stomata are devoid of a specific blue light response. In contrast, stomata from intact leaves of phot1 phot2 double mutant plants had a reduced but readily detectable response to the removal of green light and to blue and green pulses.     

Analysis of synchronous photon emissions from the bacterium Photobacterium phosphoreum during colony formation from a single cell

Light emission from Photobacterium phosphoreum was analysed during cell growth on an agar plate from a single cell to colony formation. Temporal analysis of image intensified light was set so that a quadratic window covered a single cell. Intensity of light emission from a single cell through colony formation showed an initial decrease, a prolonged lag phase, and then a rapid increase. These responses on an agar plate were similar to those from liquid cultures. The image analysis showed repeated bursts of light emission in the phases when light was increasing and decreasing. Statistical analysis of light emission also emphasized the presence of bursts of light emission, suggesting the metabolic synchronism of luciferase reactions in either a single cell or synchronously divided cells. The repetitive bursts of light occurred in a single cell and continued during the growth phase in which the cell population and the light emission was increasing. In a single cell, however, periodicity of light emission was not defined directly from fast Fourier transformation, although it was indicated on oscillation of mean level of fluctuated light emission, at initial phase of culture on agar plate.     

蓝光照射对黄瓜无翅瓜蚜驱避行为的影响

蓝光照射可以降低黄瓜Cucumis sativus上蚜虫的种群密度,但蓝光照射后无翅蚜虫是如何被驱离的尚未见报道。本文以盆栽黄瓜为供试材料,研究蓝光照射对黄瓜上无翅瓜蚜Aphis gossypii驱避行为的影响。结果表明,蓝光照射对设施黄瓜上的无翅蚜有较强的驱避作用,光照强度越大、照射时间越长,黄瓜上蚜虫的虫口减退率越大。蓝光照射后无翅蚜主要通过黄瓜主茎离开黄瓜向花盆的土下迁移,少部分蚜虫还可以顺着花盆向盆外迁移。光强越强,相同时间内迁离黄瓜的蚜虫越多。300 lux蓝光照射10 h后,蚜虫种群的校正虫口减退率达到64.03%。相同的蓝光光强和照射时间下,晚间蓝光照射处理后蚜虫的迁移数量多于白天。地面黄光环境对蓝光驱避黄瓜蚜虫具有较强的促进作用,盆外放置黄板,迁向盆外的蚜虫量增加。黄光点亮30 min后关闭,同时打开蓝光可以提高蓝光对蚜虫驱避作用。因此,蓝光照射可以驱离黄瓜上的无翅蚜,驱离的无翅蚜主要迁移到盆内土中,少量的可以迁出花盆。     

Failure of extraocular light to facilitate circadian rhythm reentrainment in humans

Although extraocular light can entrain the circadian rhythms of invertebrates and nonmammalian vertebrates, almost all studies show that the mammalian circadian system can only be affected by light to the eyes. The exception is a recent study by Campbell and Murphy that reported phase shifts in humans to bright light applied with fiber-optic pads behind the knees (popliteal region). We tested whether this extraocular light stimulus could accelerate the entrainment of circadian rhythms to a shift of the sleep schedule, as occurs in shift work or jet lag. In experiment 1, the sleep/dark episodes were delayed 8h from baseline for 2 days, and 3h light exposures were timed to occur before the temperature minimum to help delay circadian rhythms. There were three groups: (1) bright (about 13,000 lux) extraocular light from fiber-optic pads, (2) control (dim light, 10-20 lux), and (3) medium-intensity (about 1000 lux) ocular light from light boxes. In experiment 2, the sleep/dark episodes were inverted, and extraocular light was applied either before the temperature minimum to help delay circadian rhythms or after the temperature minimum to help advance rhythms. Circadian phase markers were the salivary dim light melatonin onset (DLMO) and the rectal temperature minimum. There was no evidence that the popliteal extraocular light had a phase-shifting effect in either experiment. Possible reasons for phase shifts in the Campbell and Murphy study and not the current study include the many differences between the protocols. In the current study, there was substantial sleep deprivation before the extraocular light was applied. There was a large shift in the sleep/dark schedule, rather than allowing subjects to sleep each day from midnight to noon, as in the Campbell and Murphy study. Also, when extraocular light was applied in the current protocol, subjects did not experience a change from sleeping to awake, a change in posture (from lying in bed to sitting in a chair), or a change in ocular light (from dark to dim light). Further research is necessary to determine the conditions under which extraocular light might produce phase shifts in human circadian rhythms. (Chronobiology International, 17(6), 807-826, 2000).     

Detrimental effect of visible light on meiosis of mammalian eggs in vitro

Short wavelength visible light (less than 470-480 nm) emmitted from ordinary light sources is detrimental to unfertilized hamster eggs in that prolonged exposure to the light disturbs the completion of normal meiosis after the eggs are penetrated by spermatozoa. The fluorescent light commonly used in modern laboratories is more harmful than the light from incandescent lamps. In experiments involving the handling of eggs in vitro, minimal exposure to the light or the use of appropriate filters (e.g., red cellophane sheets) is recommended.     

Effect of light quality on the organization of photosynthetic electron transport chain of pea seedlings

The activity of NADP and O₂ photoreduction by water is essentially higher in chloroplasts isolated from pea seedlings (Pisum sativum L.) grown under blue light as compared with that from plants grown under red light. In contrast, the photoreduction of NADP and O₂ with photosystem I only is practically the same or even lower in chloroplasts isolated from plants grown under blue light. The addition of plastocyanin does not affect the rate or the extent of NADP photoreduction by water in the chloroplasts isolated from plants grown under blue light, whereas it sharply activates NADP reduction in the chloroplasts isolated from plants grown under red light. The extent of the light-induced oxidation of cytochrome f is appreciably higher in chloroplasts isolated from plants grown under blue light. Cytochrome b₅₅₉ plays the predominant role in the oxidoreductive reactions of these chloroplasts. Furthermore, the fluorescence measurements indicate more effective transfer of excitation energy from chlorophyll to the photosystem II reaction center in chloroplasts isolated from plants grown under blue light.     

Photosynthetic Electron Transport in Plants of Sitka Spruce Subjected to Differing Light Environments during Growth

Seedlings of Picea sitchensis (Bong.) Carr. (Sitka spruce) have been grown in four different light regimes in growth chambers. Chloroplast fragments have been isolated from the needles and Photosystem I and Photosystem II activities measured. Measurements were made at eight photon flux densities giving light response curves for photosystem activity in needles grown in the four different light regimes. Chlorophyll concentration was higher in needles from the low cultivation light environments than in those from the high light environments. Photosystem activity was higher in needles from the high cultivation light environments. Evidence that Photosystem I was limiting photosynthesis in needles grown in the high light environments was obtained.     

LED不同光质对萝卜愈伤组织诱导、增殖和萝卜硫素含量的影响

以白水萝卜无菌苗及其愈伤组织为实验材料,研究其在LED白、红、黄、蓝、绿和蓝红6种光质下的愈伤诱导和增殖。结果表明：LED不同光质下胚轴愈伤组织的诱导效应不同,诱导率顺序依次为黄光〉红光〉蓝红光〉白光〉蓝光〉绿光;蓝光、黄光和红光有利于子叶愈伤组织的诱导;子叶诱导愈伤组织的效果较下胚轴好;LED红光下愈伤组织的增殖倍数和萝卜硫素含量均为最高。     

An immunohistochemical study of the insulin-, glucagon- and somatostatin-immunoreactive cells in the developing pancreas of the chicken embryo

The distributions and relative frequencies of insulin-, glucagon- and somatostatin-immunoreactive cells were studied in dorsal, ventral, third and splenic lobes of developing chicken pancreas during embryonic periods (10 days of incubation to hatching) by immunohistochemical methods. The regions of pancreas were subdivided into three regions: exocrine, light and dark islet. Round, oval and spherical shaped immunoreactive cells were detected in all four lobes. According to developmental stages, the types of lobes and the regions of pancreas showed various distributions and relative frequencies. In the splenic lobes, insulin, glucagon and somatostatin-immunoreactive cells were detected in exocrine, dark islet and light islet from time differentiation of splenic lobes, 13 days of incubation. The insulin- and somatostatin-immunoreactive cells of the third lobes were detected in exocrine and light islets from 10 days of incubation, and in dark islets from 15 and 11 days of incubation respectively. Glucagon-immunoreactive cells were detected in exocrine, dark and light islets from 16, 11 and 19 days of incubation respectively. These immunoreactive cells of the ventral lobes were detected in exocrine and light islets. However, dark islets were not found in this lobe. Insulin-immunoreactive cells were demonstrated from 10 days of incubation in these two regions. Glucagon-immunoreactive cells were detected from 17 days of incubation in exocrine and 16 days of incubation in the light islets. Somatostatin-immunoreactive cells were demonstrated from 11 days of incubation in exocrine and 14 days of incubation in the light islets. In the dorsal lobes, insulin-immunoreactive cells were demonstrated in exocrine, dark and light islets from 12, 14, and 13 days of incubation, respectively. Glucagon- and somatostatin-immunoreactive cells were detected in dark and light islets from 13 and 14 days of incubation, respectively. Glucagon- and somatostatin-immunoreactive cells were demonstrated from 10 and 11 days of incubation in exocrine respectively. Generally, insulin-immunoreactive cells were increased in light islets but decreased in light islets with developmental stages. However, glucagon-immunoreactive cells were decreased in light islets but increased in dark islets. In addition, somatostatin-immunoreactive cells showed the same frequencies in light and dark islets with developmental stages except exocrine which increased with developmental stages.     

Light quality influences adventitious shoot production from cotyledon explants of lettuce (<Emphasis Type="Italic">Lactuca sativa</Emphasis> L.)

Summary The influence of light quality on competence and determination for organogenesis was investigated using lettuce cotyledon explants. Lettuce seedlings from four genotypes were germinated in the dark or under white, red, or blue light. Cotyledon explants were excised and cultured on a shoot-inducing medium for 28 d under white light. Germination in the dark reduced shoot numbers, suggesting that light improves the competence of explants for organogenesis. When explants from seedlings germinated under white light were cultured under different light qualities, blue was found to inhibit shoot production while red light either promoted production or had no effect on shoot number compared to controls. Treatment with blue plus red light failed to overcome the inhibition by blue light. To ascertain the temporal responses of explants to light quality, they were cultured under red or blue light prior to transfer to the alternate treatment. Exposure to blue light within 7 d of excision permanently reduced explant competence for organogenesis. Exposure after this time had a minimal effect. These results suggest that both phytochrome and cryptochrome can regulate shoot production from lettuce cotyledon explants and blue light can only inhibit organogenesis, in lettuce, during a relatively small developmental window.