Light Spectral Quality Research Articles

Cultivo de tamarindo sob malhas coloridas: plasticidade anatômica foliar

Este trabalho teve como objetivo avaliar o efeito da alteração da qualidade espectral da luz, utilizando malhas de transmissão de luz diferenciada, sobre características da anatomia foliar em plantas de tamarindo (Tamarindus indica L.), visando à obtenção de plantas mais propícias ao plantio. Mudas de tamarindo foram cultivadas sob malhas de 50% de sombreamento nas cores branca, azul, vermelha e preta em delineamento inteiramente casualizado. Após 90 dias de cultivo sob as malhas, as folhas foram avaliadas quanto à anatomia e micromorfologia. Plantas submetidas ao cultivo sob malha branca apresentaram maior altura das células da epiderme na face abaxial e maior espessura do parênquima paliçádico e da nervura central. Melhores resultados para epiderme na face adaxial e limbo foliar foram observados sob malhas branca e azul. Maiores densidades estomáticas foram obtidas sob malhas azul e vermelha. As folhas de Tamarindus indica apresentam plasticidade anatômica em resposta às modificações no espectro da radiação. Em face desses resultados, as malhas branca e azul podem ser recomendadas para obtenção de plantas mais propícias ao plantio.

Rooting of ornamental cuttings affected by spectral light quality

Adventitious rooting is a critical process in the vegetative propagation of ornamental plants. A well-rooted cutting is essential for optimal growth and high quality plants. We investigated the use of spectral light quality to improve adventitious rooting of cuttings in three ornamental species: Chrysanthemum x morifolium, Lavandula angustifolia and Rhododendron simsii hybrids (azalea). Different combinations of red (R) and blue (B) LEDs were tested: R:B 100:0, 90:10, 80:20, 50:50, 10:90 and 0:100 at a light intensity of 60 mu mol m(-2) s(-1) for chrysanthemum and lavender and 30 mu mol m(-2) s(-1) for azalea. No natural light was supplied. The rooting quality was assessed by determining the rooting percentage, the amount of roots and the root dry weight. For all three species, rooting was highly efficient under 100% red light. Polar auxin transport was also influenced by the different light spectra as demonstrated by the use of auxin transport inhibitors. For chrysanthemum, rooting was most inhibited under 10:90 R:B, while for azalea the inhibition in rooting was highest under 50:50 R:B. The use of LEDs for rooting of ornamental cuttings is promising if it can be used in a multi-layered system. The controlled environment will lead to a year-round high quality rooted cutting production.

System responses to equal doses of photosynthetically usable radiation of blue, green, and red light in the marine diatom Phaeodactylum tricornutum.

Due to the selective attenuation of solar light and the absorption properties of seawater and seawater constituents, free-floating photosynthetic organisms have to cope with rapid and unpredictable changes in both intensity and spectral quality. We have studied the transcriptional, metabolic and photo-physiological responses to light of different spectral quality in the marine diatom Phaeodactylum tricornutum through time-series studies of cultures exposed to equal doses of photosynthetically usable radiation of blue, green and red light. The experiments showed that short-term differences in gene expression and profiles are mainly light quality-dependent. Transcription of photosynthesis-associated nuclear genes was activated mainly through a light quality-independent mechanism likely to rely on chloroplast-to-nucleus signaling. In contrast, genes encoding proteins important for photoprotection and PSII repair were highly dependent on a blue light receptor-mediated signal. Changes in energy transfer efficiency by light-harvesting pigments were spectrally dependent; furthermore, a declining trend in photosynthetic efficiency was observed in red light. The combined results suggest that diatoms possess a light quality-dependent ability to activate photoprotection and efficient repair of photodamaged PSII. In spite of approximately equal numbers of PSII-absorbed quanta in blue, green and red light, the spectral quality of light is important for diatom responses to ambient light conditions.

Shining light on benthic macroalgae: mechanisms of complementarity in layered macroalgal assemblages.

Phototrophs underpin most ecosystem processes, but to do this they need sufficient light. This critical resource, however, is compromised along many marine shores by increased loads of sediments and nutrients from degraded inland habitats. Increased attenuation of total irradiance within coastal water columns due to turbidity is known to reduce species' depth limits and affect the taxonomic structure and architecture of algal-dominated assemblages, but virtually no attention has been paid to the potential for changes in spectral quality of light energy to impact production dynamics. Pioneering studies over 70 years ago showed how different pigmentation of red, green and brown algae affected absorption spectra, action spectra, and photosynthetic efficiency across the PAR (photosynthetically active radiation) spectrum. Little of this, however, has found its way into ecological syntheses of the impacts of optically active contaminants on coastal macroalgal communities. Here we test the ability of macroalgal assemblages composed of multiple functional groups (including representatives from the chlorophyta, rhodophyta and phaeophyta) to use the total light resource, including different light wavelengths and examine the effects of suspended sediments on the penetration and spectral quality of light in coastal waters. We show that assemblages composed of multiple functional groups are better able to use light throughout the PAR spectrum. Macroalgal assemblages with four sub-canopy species were between 50–75% more productive than assemblages with only one or two sub-canopy species. Furthermore, attenuation of the PAR spectrum showed both a loss of quanta and a shift in spectral distribution with depth across coastal waters of different clarity, with consequences to productivity dynamics of diverse layered assemblages. The processes of light complementarity may help provide a mechanistic understanding of how altered turbidity affects macroalgal assemblages in coastal waters, which are increasingly threatened by diminishing light quantity and altered spectral distributions through sedimentation and eutrophication.

Effect of Light Spectral Quality on Essential Oil Components in Ocimum Basilicum and Salvia Officinalis Plants

In plants grown with artificial lighting, variations in light spectral composition can be used for the directed biosynthesis of the target substances including essential oils, e.g. in plant factories. We studied the effect of light spectral quality on the essential oil composition in Ocimum basilicum and Salvia officinalis plants grown in controlled environment. The variable-spectrum light modules were designed using three types of high-power light-emitting diodes (LEDs) with emission peaked in red, blue and red light, white LEDs, and high-pressure sodium lamps as reference. Qualitative and quantitative essential oil determinations were conducted using gas chromatography with mass selective detection and internal standard method.Sweet basil plant leaves contain essential oils (са. 1 %) including linalool, pinene, eugenol, camphor, cineole, and other components. And within the genetic diversity of the species, several cultivar groups can be identified according to the flavor (aroma) perceived by humans: eugenol, clove, camphor, vanilla basil. Essential oil components produce particular flavor of the basil leaves. In our studies, we are using two sweet basil varieties differing in the essential oil qualitative composition – “Johnsons Dwarf” (camphor as a major component of essential oils) and “Johnsons Lemon Flavor” (contains large amount of citral defining its lemon flavor).In sage, essential oil composition is also very variable. As for the plant responses to the light environment, the highest amount of the essential oils was observed at the regimes with white and red + blue LED light. And it was three times less with red light LEDs alone. In the first two environments, thujone accumulation was higher in comparison with camphor, while red LED light and sodium lamp light favored camphor biosynthesis (three times more than thujone). The highest amount of eucalyptol was determined in plants grown with red LEDs.

Does light spectral quality affect survival and regeneration of potato (Solanum tuberosum L.) shoot tips after cryopreservation?

Cryopreservation, the storage of germplasm at ultra-low temperature is the most reliable tool for long-term preservation of plant genetic resources. Cryopreservation techniques are widely applied but the effect of light spectra on plant recovery after cryopreservation is largely unknown. Therefore, we investigated the effect of different light spectral qualities on survival and regeneration of shoot tips of potato (Solanum tuberosum L.) cultivars Agrie Dzeltenie, Maret, Bintje, Desiree and Anti cryopreserved by the DMSO-droplet method. Prior to cryopreservation, the plants were stored under cool white fluorescent light (CW). Post-cryopreservation, the plants were allowed to regenerate under six different light qualities: CW, warm white light (HQI), blue LEDs (B), red LEDs (R), red with 10 % of blue (RB) and RBF - red with 10 % of blue with addition of 20 % of far-red LEDs. The light spectral quality had a significant effect on the survival and regeneration of potato shoot tips after cryopreservation. The combination of red light with 10 % of blue (RB) doubled the regeneration percentage of all cultivars, whereas red light (R) was not suitable for regeneration after cryopreservation. Specifically, the regeneration percentages were increased in RB compared to CW from 25.5 to 52.6 % for ‘Agrie Dzeltenie’, 25.0–43.6 % for ‘Maret’, 8.1–26.1 % for ‘Bintje’, 0.0–17.1 % for ‘Anti’ and 18.2–36.6 % for ‘Desiree‘. Therefore, the modification of light spectra during the recovery phase is a promising tool for increasing the regeneration of potato shoot tips after cryopreservation.

English

This study aimed to evaluate  the effect of spectral light quality on different anatomical features of banana tree plantlets grown under coloured shade nets. Banana plants of five genotypes (Maçã, Thap Maeo, Caipira, BRS Platina and Princesa), obtained from micropropagation, were grown under white, blue, red and black nets, with shade of 50%, in a completely randomized design. After 90 days of acclimatization under nets, the leaves were collected and analyzed anatomically following basic protocol of plant microtechnique. Cultivation under white net provided greater thickness of epidermis cells, hypodermis on the adaxial face and palisade parenchyma; and greater stomatal density on the adaxial face; both the red and white nets, however, increased stomatal density on the abaxial face. The use of white net, during the acclimatization phase, is recommended  for cultivation of banana plantlets obtained of micropropagation.   Key words: Musa sp., acclimatization, spectral quality, anatomical plasticity.

A hundred years of color studies in insects: with thanks to Karl von Frisch and the workers he inspired.

and colleagues (Hempel de Ibarra et al. 2014). Lars Chittka and colleagues specifically remind us that whilst bees and other insects see in color, in complex natural environments color perception can be a challenging cue due to the large changes in the spectral quality of light in different foraging environments (Chittka et al. 2014). Anne Leonard and Pavel Masek (2014) discuss the latest evidence that bees can use multimodal information combining both color and olfactory cues to help reduce uncertainty in complex foraging conditions. Indeed there is currently a lot of interest in how bees make decisions in complex environments. Aurore Avargues-Weber and Martin Giurfa (2014) discuss that a variety of important factors like conditioning method can influence bee perception, possibly through cognitive ‘top-down’ attention-type mechanisms. Further evidence of complex decision making in bees comes from a nice study on bumblebees by Lisa Evans and Nigel Raine (2014) who show that the way in which some bees make errors may be of adaptive advantage for selecting novel rewarding colors in natural conditions. Other studies show us that since the time of von Frisch color processing has been tested in a wide variety of different insect species. Motohiro Wakakuwa and colleagues (2014) discuss photoreceptor sensitivity in the leafhopper (Nephotettix cincticeps) which shows some behavioral sensitivity to long wavelength ‘infrared’ radiation. Francismeire Telles and colleagues (2014) show in the hummingbird hawkmoth (Macroglossum stellatarum) that the behavioral sensitivity to blue wavelength light is much higher than predicted from the retinal photoreceptor sensitivity, which may be related to the innate preference of hawkmoths for blue flowers. Besides bees, flies and butterflies have been well studied. Klaus Lunau (2014) provides a timely review on the color vision of flies which is a system generating a lot of interest at present. Michiyo Kinoshita About 100 years ago it was often thought the world might appear pretty dull for insects until the publication of Karl von Frisch in 1914. this ground breaking study by von Frisch revealed that free flying honeybees could be trained with sucrose solution to visit a colored card, and choose this stimulus correctly in tests when placed amongst a variety of grey cards. the logic of the experiment, done at a time when the spectral sensitivities of bee photoreceptors were unknown, was that if bees were only using an achromatic mechanism to find the conditioned, colored stimulus associated with a sucrose reward then the bees would make mistakes for grey cards having similar brightness values to the colored stimulus. However, the bees reliably chose the colored stimulus amongst many shades of grey (von Frisch 1914), and the eyes of the next generations of researchers were opened to the refinement and diversity of color perception in bees and other insects (Kuhn 1927; Daumer 1956; Menzel 1967; Helversen 1972; Giurfa 2004). this current year of 2014 also marks the 50th anniversary of the first publication of the spectral sensitivities of individual photoreceptor cells in the honeybee by Autrum and von Zwehl (1964), which further helped to establish honeybees as a classic model for research into insect color vision (Peitsch et al. 1992; Briscoe and Chittka 2001). In this special issue of The Journal of Comparative Physiology A, leading scientists in the field have teamed up to pay tribute to the important start Karl von Frisch gave to the field of neuroethology and insect vision with his publication in 1914. Basic physiology and ecology of bee color vision is summarized by Natalie Hempel de Ibarra

LEDs light spectrum effect on the success of fragmentation and growth of the leather coral Sarcophyton spp.

LEDs light spectrum effect on the success of fragmentation and growth of the leather coral Sarcophyton spp.

Survey of How Hanging Baskets Influence the Light Environment at Lower Crop Level in Ornamental Greenhouses in Ontario, Canada

Hanging basket (HB) production alters the light environment in the lower canopy of ornamental greenhouses by intercepting and altering the spectral quality of incoming light. If shading is sufficiently high, the quality of the lower crops can be reduced. This work investigated changes in light quantity and quality at the lower crop level caused by HB production in Ontario, Canada. Light sampling occurred at three commercial greenhouse facilities throughout the Spring 2012 HB season. The greenhouses represented a range of HB densities (1.8, 2.4, and 3.0 baskets/m2) and different HB canopy architectures (one, two, and three tiers of HBs). Light samples were taken at three fixed locations within each greenhouse facility: outside, HB level, and lower crop level. Photosynthetically active radiation (PAR) was logged continuously at each location within each greenhouse environment. Spectral scans were made at each sampling location, within each greenhouse facility, at various times throughout the season to assess how HB production altered the red to far red ratio (R:FR) at lower crop level. As the season progressed, outdoor daily light integrals (DLIs) more than doubled from <20 to >40 mol·m−2·d−1. Light reduction caused by polyethylene films and structural components varied among locations, but remained steady throughout the season, averaging 48.3% for the three locations. As the HB crops matured, the rate of decrease in PAR at lower crop level varied according to facility and HB density with mean reductions of 42.5%, 32.6%, and 37.7% for the one-, two-, and three-tiered facilities, respectively. Mean lower crop level DLIs were all very similar, between 9.4 and 9.9 mol·m−2·d−1. Accordingly, there may be insufficient light below HB canopies to produce high-quality crops of many varieties of bedding plants that are commonly grown in Ontario. The one- and two-tiered systems reduced the R:FR at lower crop level by 14% and 10%, respectively, whereas the three-tiered system caused no reduction. More work is required to determine if the observed far red shift is sufficient to alter crop quality. These case studies provide a backdrop against which to help determine and interpret horticultural management strategies for a variety of greenhouse crops.

Composition of essential oil from Lippia graveolens. Relationship between spectral light quality and thymol and carvacrol content

Content of thymol and carvacrol in Lippia graveolens essential oil was studied in response to variations in the spectral quality of light through the use of specific filters. Red, blue and transparent filters were used in the experiment. The plants responses were determined by internode distance and number of flowers. Responses in the essential oil were determined by thymol+carvacrol percentage and thymol:carvacrol ratio (T:C). The thymol+carvacrol percentage increased from 34% to 69% in red and from 34% to 87% in blue treatment. T:C ratio shows 1:1.5, 1:1.7 and 2.8:1 in control, red and blue treatments, respectively. Composition, especially T:C ratio, is an important factor in the quality of this essential oil because of its influence in biological activity.

Athletic Field Paint Color Differentially Alters Light Spectral Quality and Bermudagrass Photosynthesis

ABSTRACTPainting of athletic fields is widespread throughout the world and can often cause declines in turfgrass health. Visible light and photosynthesis share the same wavelengths (400–700 nm), and it was hypothesized that alterations in visible light to produce specific colors would lead to reductions in photosynthetically active radiation (PAR) and total canopy photosynthesis (TCP). Lab experiments using a spectroradiometer and LICOR 1800‐12 integrating sphere examined the impacts of 10 colors of athletic field paint on PAR as well as wavelengths within PAR. These colors were then applied weekly for 5 wk to ‘Tifway’ bermudagrass [Cynodon dactylon (L.) Pers. × Cynodon transvaalensis Burtt Davy], and TCP was measured using a gas exchange system 24 h after each application. Spectroradiometry analyses revealed the significant effects of paint color (P ≤ 0.001) on reflection, transmission, and absorption of PAR. Lighter colors including white, yellow, orange, and red reflected 47 to 92% of PAR while darker colors including green, black, and dark blue absorbed 87 to 95% of PAR. Accompanying gas exchange measurements revealed that TCP was most negatively correlated with absorption of PAR (r = −0.959, P ≤ 0.001) and that darker colors negatively impact TCP more than lighter colors. The results clearly indicate that damage to turfgrasses with long‐term painting will be difficult to avoid, and this is particularly true with darker colors of paint.

Isoprenoid emissions, photosynthesis and mesophyll diffusion conductance in response to blue light

The effects of blue light (BL) on leaf gas exchange of Populus×canadensis, a strong isoprene emitter, and Quercus ilex and Citrus reticulata, two monoterpene emitters with respectively small and large storage pools for monoterpenes, were studied. Leaves were initially exposed to a saturating photosynthetic photon flux density (PPFD) of white light (WL), which was then progressively reduced to perform WL-response curves. Leaves acclimated to saturating WL were then quickly exposed to equivalent BL levels to perform BL-response curves. Blue light did not significantly affect photosynthetic parameters in the light-limited portion of the PPFD-response curves in both P.×canadensis and Q. ilex. Whereas photosynthesis (A), stomatal conductance (gs), and mesophyll conductance (gm) were significantly decreased at high PPFDs of BL. A was similarly inhibited by BL in C. reticulata, but there was no significant effect of light quality on gs. Overall these results show that the negative effect of BL on photosynthesis is widespread in tree species with different leaf characteristics, and that this involves coordinated reductions in gs and gm. BL negatively affected isoprene emission and, to a lesser extent monoterpene emissions, in concert with photosynthetic inhibition. Interesting, both isoprene and monoterpene emissions were shown to be inversely dependent upon intercellular [CO2]. These results indicate that a change in light spectral quality, which can vary during the day, between days and within seasons, can alter photosynthesis and isoprenoid emissions, depending on the PPFD intensity. Such effects should be strongly considered in photosynthesis and volatile isoprenoid emission models.

Production of volatiles by the red seaweed Gelidium arbuscula (Rhodophyta): emission of ethylene and dimethyl sulfide.

The effects of different light conditions and exogenous ethylene on the emission of volatile compounds from the alga Gelidium arbuscula Bory de Saint-Vincent were studied. Special emphasis was placed on the possibility that the emission of ethylene and dimethyl sulfide (DMS) are related through the action of dimethylsulfoniopropionate (DMSP) lyase. The conversion of DMSP to DMS and acrylate, which is catalyzed by DMSP lyase, can indirectly support the synthesis of ethylene through the transformation of acrylate to ethylene. After mimicking the desiccation of G.arbuscula thalli experienced during low tides, the volatile compounds emitted were trapped in the headspace of 2mL glass vials for 1h. Two methods based on gas chromatography/mass spectrometry revealed that the range of organic volatile compounds released was affected by abiotic factors, such as the availability and spectral quality of light, salinity, and exogenous ethylene. Amines and methyl alkyl compounds were produced after exposure to white light and darkness but not after exposure to exogenous ethylene or red light. Volatiles potentially associated with the oxidation of fatty acids, such as alkenes and low-molecular-weight oxygenated compounds, accumu-lated after exposure to exogenous ethylene and red light. Ethylene was produced in all treatments, especially after exposure to exogenous ethylene. Levels of DMS, the most abundant sulfur-compound that was emitted in all of the conditions tested, did not increase after incubation with ethylene. Thus, although DMSP lyase is active in G.arbuscula, it is unlikely to contribute to ethylene synthesis. The generation of ethylene and DMS do not appear to be coordinated in G.arbuscula.

Athletic Field Paint Impacts Light Spectral Quality and Turfgrass Photosynthesis

ABSTRACTAthletic field paints are applied to turf surfaces with little or no acute injury. However, field managers notice chronic declines in turfgrass health after repeated applications. This study examines athletic field paint impacts on spectral quality and associated turfgrass photosynthesis. Growth chamber experiments evaluated effects of red and white athletic field paint as well as one, two, three, and four repeated weekly applications on total canopy photosynthesis (TCP) of perennial ryegrass (Lolium perenne L.). Paint treatments were applied weekly for 6 wk with TCP recorded 24 h after each application using a gas exchange system. Spectroradiometry experiments evaluated reflection, absorption, and transmission of light at various wavelengths based on paint color, dilution, and thickness. Over a six week period all treatments reduced TCP based on color (P ≤ 0.0001) and dilution (P ≤ 0.0001). Red no‐dilution paint produced a 75% reduction in TCP over 6 wk while white 1:1 diluted paint only produced a 19% reduction. Spectroradiometry data suggests this is likely due to reductions in photosynthetically active radiation (PAR) with red paint absorbing 51% of incident PAR while transmitting and reflecting 6 and 43%, respectively. White paint transmitted 5% of PAR while reflecting 95%. Alterations in light spectral quality resulting from athletic field paint applications can impact PAR, which may result in reduced turfgrass health.

NITROGEN FIXATION, HYDROGEN CYCLING, AND ELECTRON TRANSPORT KINETICS IN TRICHODESMIUM ERYTHRAEUM (CYANOBACTERIA) STRAIN IMS101(1).

This study describes the relationships between dinitrogen (N2 ) fixation, dihydrogen (H2 ) production, and electron transport associated with photosynthesis and respiration in the marine cyanobacterium Trichodesmium erythraeum Ehrenb. strain IMS101. The ratio of H2 produced:N2 fixed (H2 :N2 ) was controlled by the light intensity and by the light spectral composition and was affected by the growth irradiance level. For Trichodesmium cells grown at 50 μmol photons · m(-2) · s(-1) , the rate of N2 fixation, as measured by acetylene reduction, saturated at light intensities of 200 μmol photons · m(-2) · s(-1) . In contrast, net H2 production continued to increase with light levels up to 1,000 μmol photons · m(-2) · s(-1) . The H2 :N2 ratios increased monotonically with irradiance, and the variable fluorescence measured using a fast repetition rate fluorometer (FRRF) revealed that this increase was accompanied by a progressive reduction of the plastoquinone (PQ) pool. Additions of 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (DBMIB), an inhibitor of electron transport from PQ pool to PSI, diminished both N2 fixation and net H2 production, while the H2 :N2 ratio increased with increasing level of PQ pool reduction. In the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), nitrogenase activity declined but could be prolonged by increasing the light intensity and by removing the oxygen supply. These results on the coupling of N2 fixation and H2 cycling in Trichodesmium indicate how light intensity and light spectral quality of the open ocean can influence the H2 :N2 ratio and modulate net H2 production.

Early Developmental Responses to Seedling Environment Modulate Later Plasticity to Light Spectral Quality

Correlations between developmentally plastic traits may constrain the joint evolution of traits. In plants, both seedling de-etiolation and shade avoidance elongation responses to crowding and foliage shade are mediated by partially overlapping developmental pathways, suggesting the possibility of pleiotropic constraints. To test for such constraints, we exposed inbred lines of Impatiens capensis to factorial combinations of leaf litter (which affects de-etiolation) and simulated foliage shade (which affects phytochrome-mediated shade avoidance). Increased elongation of hypocotyls caused by leaf litter phenotypically enhanced subsequent elongation of the first internode in response to low red∶far red (R∶FR). Trait expression was correlated across litter and shade conditions, suggesting that phenotypic effects of early plasticity on later plasticity may affect variation in elongation traits available to selection in different light environments.

Variações anatômicas de Laelia purpurata var. cárnea cultivada in vitro sob diferentes intensidades e qualidade spectral de luz

Plantas de Laelia purpurata var. cárnea propagadas in vitro e mantidas em sala de crescimento e em casa de vegetação foram submetidas a diferentes intensidades e qualidade espectral de luz, envolvidas com diferentes malhas coloridas: azul, vermelha e preta. Foi observado que a intensidade e qualidade espectral de luz interferiram de forma significativa em todos os parâmetros analisados, aos 120 dias de cultivo. Plantas cultivadas sob malha azul em sala de crescimento e casa de vegetação apresentaram maior espessamento da epiderme na face adaxial (31,73 e 35,46µm), respectivamente, diferindo estatisticamente quando comparado com os demais tratamentos. Foi observado aumento significativo no número de camadas de células do velame em raízes de plantas cultivadas em casa de vegetação, independente da malha de sombreamento, quando comparadas com as de sala de crescimento. Em secções transversais de raízes de plantas cultivadas em casa de vegetação sob malha azul, foi observada maior diferenciação dos tecidos (velame, exoderme, córtex e cilindro vascular).

Dramatic scenario of urogenital Candida albicans in presence of Lactic acid bacteria (LAB Effects of different light treatments on the natural transformation of Synechocystis sp. strain PCC 6803)

Although many factors that affect the frequency of natural transformation of the unicellular cyanobacterium Synechocystis have been extensively reported, little is known regarding the effects of changes in the spectral quality and intensity of light on its natural transformation. The frequency of natural transformation was significantly enhanced or inhibited by the treatments with low light (LL) or high light (HL) under the incubation condition of cells and DNA before plating and/or on the plates in comparison with that by the treatment with growth light (GL); the changes in the spectral quality of light did not remarkably affect the transformation efficiency of Synechocystis. Further, the lengths of the appearance time of transformants were shortened or retarded by HL or LL illumination when cells and DNA were incubated on the plates relative to that by GL illumination. Further, the transformation efficiency of Synechocystis was closely associated with the permeability of the cell membranes. Treatment with LL significantly enhances the frequency of natural transformation whereas HL illumination remarkably shortens the appearance time of Synechocystis transformants. These phenomena can be extensively applied to future studies according to the specific demands of the transformation experiments. Possible mechanisms underlying these phenomena are discussed. Key words: Appearance time of transformants, light treatments, natural transformation,Synechocystis, transformation efficiency.

Responses of the invasive Ricinus communis seedlings to competition and light

Ricinus is an invasive species. We assessed its responses to intra- and interspecific competition, and different intensities and spectral qualities of light. To evaluate resource portioning, we obtained biomass measurements of juveniles in different densities of co-specifics and another species; we also compared the proportion of juveniles to determine if there is recruitment limitation. We obtained the same information for juveniles growing in different photosynthetic photon flux densities (PPFD) and ratios of red to far-red wavelengths (R/FR). Competition and light did not limit recruitment, resulting in differences in biomass allocation only. Biomass decreased more for plants subjected to interspecific competition than to intraspecific competition, suggesting that Ricinus is both a poor intra- and interspecific competitor. Juveniles growing under reduced PPFD and R/FR differed in biomass allocation and morphology as do shade-intolerant species subjected to shading. Our results show that Ricinus presents high plasticity, which may contribute to its invasion ability.