Search

The implementation of a conservation program since the early 1980s resulted in a reduction in phosphorus concentrations in Lake Geneva. However, in the 1990s, phytoplankton biomass increased again, almost reaching the high values recorded during the period of greatest P loading. The structural changes in the phytoplankton of Lake Geneva over the past 25 yr have been analyzed using a recently developed statistical method based on hierarchical clustering and Bayesian probabilities. This method has been used to identify phytoplankton assemblages and to map annual and interannual successional patterns simultaneously. Characteristic species were identified for each cluster after calculation of their relative species fidelity and specificity indices. Six distinct phytoplankton assemblages were identified, and although the way species are organized into communities remains unclear, the seasonal patterns of succession are consistent with the C-S-R adaptive strategies and are characteristic of temperate lakes. This pattern broadly recurred over the years, but was markedly influenced by both human activity and regional climatic changes: The warmer winters and springs recorded in Europe since 1988 led to an earlier clear-water phase. In the 1990s, the earlier and deeper depletion of dissolved inorganic phosphorus led to colonization in the summer by large species tolerant of low light levels and that could develop deeper in the water column, where phosphorus was still abundant. Their size made them less vulnerable to grazing losses, which favors their accumulation and lead to an unexpected high biomass in recent years.

The temperate anemone Anthopleura elegantissima hosts two phylogenetically different symbiotic microalgae, a dinoflagellate Symbiodinium (zooxanthellac, ZX) and a chlorophyte (zoochlorellae, ZC), throughout certain regions of its latitudinal range. Because of the broad intertidal and geographic range of this anemone, we examined the role of irradiance to ascertain which specific symbiotic parameters are affected and whether light intensity governs the observed distributions of natural populations of ZX and ZC. Irradiance appears to be a key factor in regulating both the photophysiology and metabolism of this alga-cnidarian association. Regardless of light intensity, algal densities remained stable for anemones harboring ZX or ZC, whereas the mitotic indices of ZX and ZC both varied directly with light intensity. The chlorophyll content of ZX remained fairly constant regardless of irradiance; in contrast, ZC chlorophyll content was inversely proportional to light intensity. Regardless of irradiance, the carotenoid content of both symbionts was constant; however, ZX carotenoid levels were higher than those of ZC. Net photosynthesis was directly related to light intensity for both algal symbionts and ZX photosynthetic rates were consistently higher than those of ZC. Similarly, the potential carbon contribution of ZX and ZC to animal respiration (CZAR) displayed a direct relationship with light intensity, peaking at 800 [micro]mol*[m.sup.-2]*[s.sup.-1], then subsequently declined. Lower ZX growth rates, coupled with higher photosynthetic rates and higher CZAR estimates, compared to ZC, suggest that the ZX should be the dominant symbiont as light intensity increases; this may explain the high densities of anemones in the field containing ZX where the levels of irradiance are naturally high. These results support the interpretation that irradiance is a significant environmental parameter that dictates the microhabitat and latitudinal distribution of the two symbiotic algal taxa. This is the second in a series of papers examining the physical parameters that influence the distribution of ZX- and ZC-bearing A. elegantissima.

We examined the role of irradiance in the regulation of photosynthetic performance in a dense (1700 shoots [m.sup.-2]) population of the seagrass Thalassia testudinum Banks ex Konig exposed to high irradiance and low nutrient availability, located in the Mexican Caribbean. The results indicate that leaf self-shading strongly modifies the light environment within the seagrass canopy. An individual leaf section experiences, during leaf elongation, a photon flux density gradient that changes by three orders of magnitude. This variation leads to site-specific photosynthetic performance, not predictable from descriptions of the optical characteristics of the water column above the canopy. Reductions in pigment content and leaf absorptance towards the apical regions of the second youngest leaf were accompanied with permanent reductions in the quantum yield of photosystem II ([F.sub.v]/[F.sub.m]) as a consequence of an accumulation of inactive reaction centers ('chronic photoinhibition'). These changes were strongly associated with the number of hours that a particular leaf section is exposed to supersaturating irradiance, but are not indicative of photoinhibition sensu stricto, as we did not find any significant difference in the photosynthetic response of basal and apical leaf sections to increasing irradiance. Apical leaf sections experienced a fivefold midday reduction in [F.sub.v]/[F.sub.m] compared with the small but significant reduction shown by basal sections. It is highly probable that incomplete diurnal recovery of the light-dependent midday [F.sub.v]/[F.sub.m] reduction ('dynamic photoinhibition') causes the observed age-dependent [F.sub.v]/[F.sub.m] loss experienced by T. testudinum leaves. Comparison of the estimates of integrated daily production from physiological data indicate a dramatic overestimation of daily production by the values obtained using only optical characteristics of the water column and excluding light attenuation within the canopy.

In this paper the results of investigations into atmospheric aerosol optical depth (AOD) over the Atlantic Ocean are discussed. The data were collected during five shipboard expeditions that took place between 1989 and 1996. Measurements were taken by a 0.37-4-[micro]m multiwavelength sun photometer, specially designed for working conditions on board a ship. The analysis focuses on the spatial variability of atmospheric transparency and the spectral behavior of AOD in different oceanic areas. The genetic zoning of aerosol turbidity takes into account the influence of two factors: the type of continental aerosol and the character of airmass transport that dominates in a given latitudinal zone. The area selection by the genetic zoning method is further confirmed by the results of the 'sign' classification based on the spatial distributions of AOD and the Angstrom parameter. Statistical characteristics for different areas of the Atlantic are given. The mean values of AOD (0.55 [micro]m) range from 0.08 to 0.38 and the mean Angstrom parameters from 0.3 to 1.1. The spectral dependencies of AOD in the extended wavelength range (0.37-4 [micro]m) are represented as the sum of two components related to the contribution of fine and coarse aerosols. It is noted that the largest spatial inhomogeneities of integral atmospheric transparency are caused by the aerosol component, and in most areas the coarse aerosol is a principal contributor to the extinction of radiation.

This paper describes details, validation, and sensitivity analysis of a new atmosphere-soil-vegetation model. The model consists of one-dimensional multilayer submodels for atmosphere, soil, and vegetation and radiation schemes for the transmission of solar and longwave radiations in canopy. The atmosphere submodel solves prognostic equations for horizontal wind components, potential temperature, specific humidity, fog water, and turbulence statistics by using a second-order closure model. The soil submodel calculates the transport of heat, liquid water, and water vapor. The vegetation submodel evaluates the heat and water budget on leaf surface and the downward liquid water flux. The model performance was tested by using measured data of the Cooperative Atmosphere-Surface Exchange Study (CASES). Calculated ground surface fluxes were mainly compared with observations at a winter wheat field, concerning the diurnal variation and change in 32 days of the first CASES field program in 1997, CASES-97. The measured surface fluxes did not satisfy the energy balance, so sensible and latent heat fluxes obtained by the eddy correlation method were corrected. By using options of the solar radiation scheme, which addresses the effect of the direct solar radiation component, calculated albedo agreed well with the observations. Some sensitivity analyses were also done for model settings, Model calculations of surface fluxes and surface temperature were in good agreement with measurements as a whole.

As issues of environment and energy draw keen interest around the globe due to such problems as global warming and the energy crisis, LED with high optical efficiency is brought to the fore as the next generation lighting. In addition, as the national income level gets higher and life expectancy is extended, interest in the enhancement of life quality is increasing. Accordingly, the trend of lightings is changing frommere adjustment of light intensity to systemlighting in order to enhance the quality of one's life as well as reduce energy consumption.Thus, this study aims to design LED context lighting systemthat automatically recognizes the location and acts of a user in residential areas and creates an appropriate lighting environment.The proposed system designed in this study includes three types of processing: first, the creation of a lighting environment index suitable for the user's surroundings and lighting control scenarios and second, it measures and analyzes the optical characteristics that change depending on the dimming control of lighting and applies them to the index. Lastly, it adopts PIR, piezoelectric, and power sensor to grasp the location and acts of the user and create a lighting environment suitable for the current context. [ABSTRACT FROM AUTHOR]

Phytoplankton often face the dilemma of living in contrasting gradients of two essential resources: light that is supplied from above and nutrients that are often supplied from below. In poorly mixed water columns, algae can be heterogeneously distributed, with thin layers of biomass found on the surface, at depth, or on the sediment surface. Here, we show that these patterns can result from intraspecific competition for light and nutrients. First, we present numerical solutions of a reaction-diffusion-taxis model of phytoplankton, nutrients, and light. We argue that motile phytoplankton can form a thin layer under poorly mixed conditions. We then analyze a related game theoretical model that treats the depth of a thin layer of phytoplankton as the strategy. The evolutionarily stable strategy is the depth at which the phytoplankton are equally limited by both resources, as long as the layer is restricted to the water column. The layer becomes shallower with an increase in the nutrient supply and deeper with an increase in the light supply. For low nutrient levels, low background attenuation, and shallow water columns, a benthic layer occurs; for intermediate nutrient levels in deep water columns, a deep chlorophyll maximum occurs; and for high nutrient levels, a surface scum occurs. These general patterns are in agreement with field observations. Thus, this model can explain many patterns of algal distribution found in poorly mixed aquatic ecosystems.

Effects of nutrient treatments on photoacclimation of the hermatypic coral Stylophora pistillata (Esper) were studied. Studies on photoacclimation of colonies from different light regimes in the field were evaluated and used to design laboratory experiments. Coral colonies were collected in the Gulf of Eilat (Israel) from January to March 1993. Exterior branches of colonies from different depths (1 to 40 m) displayed different trends in production characteristics at reduced and very low levels of illumination. From 24 [+ or -] 3% to 12 [+ or -] 2% of incident surface photosynthetic active radiation (PA[R.sub.o]), zooxanthella population density and chlorophyll a+c per [10.sup.6] zooxanthellae increased, a trend seen in the range of light levels optimal for coral growth (90 to 30% PA[R.sub.o]). The [P.sub.max] of C[O.sub.2] per [10.sup.6] zooxanthellae decreased, while [P.sub.max] of C[O.sub.2] per [10.sup.3] polyps increased, indicating an increase in zooxanthella population density at low light levels. Proliferous zooxanthella frequency (PZF, a measure of zooxanthella division) declined significantly at light levels < 18 [+ or -] 3% PA[R.sub.o]. At the lowest levels of illumination (

Selection differences in alternative competitive environments have been studied with attention to germination timing and shade-avoidance responses. Velvetleaf, Abutilon theophrasti, was raised in three types of environments where competition for light varied. The study showed that timing of stem elongation strongly affects competitive success. Environments differing in competition timing for light select for elongation in different life-history states. This selection is dependent on the timing of emergence.

Net oxygen productivity in cultures of Monoraphidium minutum, Cryptomonas sp. and Planktothrix agardhii exposed to fluctuating and constant light conditions was measured in a laboratory incubator. The fluctuating light climate simulated a linear up and down movement in a 2 m water column at 4 different ratios of euphotic depth to mixing depth. In addition, cultures were kept at a constant light climate simulating static incubation at 0, 0.5, 1 and 2 m depth and at the depth of the mean irradiance, respectively. Integral productivity in the simulated water column was lowest when algae were incubated at constant light in different depths, highest when the algae were incubated at constant mean photon flux density (PFD) and intermediate under fluctuating light. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Several studies sustained the possibility that a photochemical reflectance index (PRI) directly obtained from satellite data can be used as a proxy for ecosystem light use efficiency (LUE) in diagnostic models of gross primary productivity. This modelling approach would avoid the complications that are involved in using meteorological data as constraints for a fixed maximum LUE. However, no unifying model predicting LUE across climate zones and time based on MODIS PRI has been published to date. In this study, we evaluate the effectiveness with which MODIS-based PRI can be used to estimate ecosystem light use efficiency at study sites of different plant functional types and vegetation densities. Our objective is to examine if known limitations such as dependence on viewing and illumination geometry can be overcome and a single PRI-based model of LUE (i.e. based on the same reference band) can be applied under a wide range of conditions. Furthermore, we were interested in the effect of using different faPAR (fraction of absorbed photosynthetically active radiation) products on the in-situ LUE used as ground truth and thus on the whole evaluation exercise. We found that estimating LUE at site-level based on PRI reduces uncertainty compared to the approaches relying on a maximum LUE reduced by minimum temperature and vapour pressure deficit. Despite the advantages of using PRI to estimate LUE at site-level, we could not establish an universally applicable light use efficiency model based on MODIS PRI. Models that were optimised for a pool of data from several sites did not perform well. [ABSTRACT FROM AUTHOR]

This study was intended to analyze the metabolic pathway of Rumex obtusifolius L. (Broad-leaved dock), destructive weeds worldwide, in relation to major environmental factors (light and temperature). It was found that R. obtusifolius can be classified as plants in accumulating major organic acids such as oxalate in leaves and citrate in stems (Miyagi et al., Metabolomics 6:146-155 ). The organ specific accumulation of certain metabolites was dissected by metabolomics approach in relation to metabolic pathway. Light or dark experiments showed that in the case of the oxalate accumulation, the major or the most dominated pathway was found to be the citrate-isocitrate-oxalate shunt. Furthermore, under the dark and/or low temperature (5°C) leaves showed sustainable growth with normal accumulation of TCA metabolites. Unlike leaves, there was a different pattern of metabolite accumulation in stems. Other metabolites such as amino acids also showed the organ specific alterations under the different ambient environments. [ABSTRACT FROM AUTHOR]

Eight light-intensity treatments (natural light, continuous darkness, and 15, 30, 60, 125, 250 and 500 lx under LD 12:12 cycle) were used to investigate the effects of light intensity on the daily activity of 30.27±3.08 g sea cucumber Apostichopus japonicus (Selenka). Cyclic nocturnal activity patterns of behaviour were observed at different light intensities in the range of 15-500 lx under LD 12:12 cycle. And an ongoing nocturnal cycle persisted in DD cycle for up to 8 days, but longer feeding time and less marked rhythm occurred at continuous darkness. Under poor light conditions ( I<5.18 lx), the daily activity rhythm of A. japonicus was governed by an innate biological clock and the effect of light intensity was not significant among different treatments. And more individuals tended to retreat to shelters (from 56.04% to 91.83%) with the increase of light intensity within the weak light condition (from 5.18 to 278 lx). However, the daily behaviours of A. japonicus were influenced under strong light conditions (>278 lx). Less than 8.17% individuals kept actively feeding and the proportion was not decreased with the increase of light intensity. [ABSTRACT FROM AUTHOR]

Several Heliconius L. butterflies species form nocturnal aggregations in sites with a particular architecture. Roosts are usually formed under relatively dense vegetation mats where dry vines or branches provide a perch for the night. These sites may last for months. To understand the importance of factors related to the expression of Heliconius roosting, data on light, temperature, relative humidity, wind, and use of wing color cues were recorded at H. erato and H. sara roost sites in Costa Rica and Panama in 2008 and 2009. The results show that roost sites offer reduced light conditions at dusk, provide a drier environment compared with its vicinity, and offer protection from wind and rain. Moreover, individuals use wing color recognition under reduced light conditions at dusk to successfully assemble aggregations. These findings provide key information for future experiments to study the use of landmarks, hygrosensitivity, and dim-light eye adaptations in Heliconius navigation to find roost sites. [ABSTRACT FROM AUTHOR]

Plants use light as a source of energy for photosynthesis and as a source of environmental information perceived by photoreceptars. Testing whether plants can complete their cycle if light provides energy but no information about the environment requires a plant devoid of phytochromes because all photo- synthetically active wavelengths activate phytochromes. Producing such a quintuple mutant of Arabidopsis thaliana has been challenging, but we were able to obtain it in the flowering locus T (ft), mutant background. The quintuple phytochrome mutant does not germinate in the FT background, but it germinates to some extent in the ft background. If germination problems are bypassed by the addition of gibberellins, the seedlings of the quintuple phytochrome mutant exposed to red light produce chlorophyll, indicating that phytochromes are not the sole red- light photoreceptors, but they become developmentally arrested shortly after the cotyledon stage. Blue light bypasses this block- age, rejecting the long-standing idea that the blue-light receptors cryptochromes cannot operate without phytochromes. After growth under white light, returning the quintuple phytochrome mutant to red light resulted in rapid senescence of already expanded leaves and severely impaired expansion of new leaves. We conclude that Arabidopsis development is stalled at several points in the presence of light suitable for photosynthesis but providing no photomorphogenic signal. [ABSTRACT FROM AUTHOR]

The article presents a study which investigates the stressors impact on the dynamic and morphometic seagrass Zostera noltii. It mentions that the Zostera noltii undergo a factorial mesocosm experiment wherein the seagrass was subjected to three unidirectional flow velocities using small flume tanks and contrasting light levels. The result shows that the survival rate for the single experimental plant units (EPU) were significantly low in the high velocity (HV) and medium velocity (MV) treatment. It states that the plants dynamic features were affected by the light in spite of the velocity treatment, with higher appearance rates for shoots and EPU morphometry. It adds that the light acts as the driving force for morphologic and dynamic acclimation when the stressors act at the same time.

Abstract: Germination and survival in the initial months represent a critical period for forest species. Many factors have significant influences and can produce a negative effect on regeneration. To prevent this, these factors must be known and their influence must be evaluated. The influence of light and of water availability has been studied in the most important pine species in the Iberian Peninsula, the Pinus pinaster. An experimental seed-sowing was conducted in the Cuéllar experimental site (central Spain), where four different harvest intensities were applied in 2004. Four different watering regimes were performed during two consecutives summers (2006 and 2007) and seedling development was monitored during 18 months. Main findings reveal that, regarding germination and survival in the initial months, light was more important than water availability. Higher germination and survival rates were obtained when the lowest level harvest was applied. However, in terms of biomass and growth, water availability was more influential than harvest intensity. Results improved when there was greater water availability after a few months. The main conclusion of this study is that light shows a higher impact that summer rainfall with respect to germination and survival in the early stages of Mediterranean Maritime Pine. [Copyright &y& Elsevier]

The article presents a study on forest developments using the inventory data derived from six beech reserves in Switzerland. It explores on the observation that the decrease in light is one factor for loss of invasive species in forests. Moreover, the findings intend to refine forest management systems and to develop conservation strategies.

Release of dormancy and induction of seed germination are complex traits finely regulated by hormonal signals and environmental cues such as temperature and light. The Red (R):Far-Red (FR) phytochrome photoreceptors mediate light regulation of seed germination. We investigated the possible involvement of heterotrimeric G-protein complex in the phytochrome signaling pathways of Arabidopsis thaliana seed germination. Germination rates of null mutants of the alpha (Gα) and beta (Gβ) subunits of the G-protein (At gpa1-4 and agb1-2, respectively) and the double mutant ( agb1-2/gpa1-4) are lower than the wildtype (WT) under continuous or pulsed light. The Gα and Gβ subunits play a role in seed germination under hourly pulses of R lower than 0.1 μmol m−2 s−1 whereas the Gβ subunit plays a role in higher R fluences. The germination of double mutants of G-protein subunits with phyA-211 and phyB-9 suggests that AtGPA1 seems to act as a positive regulator of phyA and probably phyB signaling pathways, while the role of AGB1 is ambiguous. The imbibition of seeds at 4°C and 35°C alters the R and FR light responsiveness of WT and G-protein mutants to a similar magnitude. Thus, Gα and Gβ subunits of the heterotrimeric G-protein complex modulate light induction of seed germination by phytochromes and are dispensable for the control of dormancy by low and high temperatures prior to irradiation. We discuss the possible indirect role of the G-protein complex on the phytochrome-regulated germination through hormonal signaling pathways. [ABSTRACT FROM AUTHOR]

Ecological consequences of shrub encroachment are emerging as a key issue in the study of global change. In mesic grasslands, shrub encroachment can result in a fivefold increase in ecosystem leaf area index (LAI) and a concurrent reduction in understory light and herbaceous diversity. LAI and light attenuation are often higher for shrub thickets than for forest communities in the same region, yet little is known about the contribution of sunflecks in shrub-dominated systems. Our objective was to compare fine-scale spatial and temporal dynamics of understory light in shrub thickets to the light environment in typical forest communities. We used an array of quantum sensors to examine variation in diffuse and direct light and determined the relative contribution of sunflecks during midday in Morella cerifera shrub thickets, a 30-yr-old abandoned Pinus taeda plantation, and a mature, second-growth, deciduous forest. Instantaneous photosynthetic photon flux density (PPFD) was measured at 1-s intervals at five sites in each community during midday. In summer, understory light during midday in shrub thickets was ∼0.8% of above-canopy light, compared to 1.9% and 5.4% in pine and deciduous forests, respectively. During summer, PPFD was uncorrelated between sensors as close as 0.075 m in shrub thickets compared to 0.175 m and 0.900 m in pine and deciduous forests, respectively, indicating that sunflecks in shrub thickets were generally small compared to sunflecks in the two forests. Sunflecks in shrub thickets were generally short (all <30 s) and relatively low in intensity (<150 μmol photons·m-2·s-1) and contributed only 5% of understory light during midday. Sunflecks were longer (up to 6 minutes) and more intense (up to 350 μmol photons·m-2·s-1) in the two forest communities and contributed 31% and 22% of understory light during midday in pine and deciduous forest, respectively. The combination of high LAI and relatively short-stature of M. cerifera shrub thickets produces a dense canopy that reduces both diffuse light and the occurrence of sunflecks. The lack of sunflecks may limit the number of microsites with a favorable light environment and contribute to the reduction in understory cover and diversity within the shrub thickets. [ABSTRACT FROM AUTHOR]

Diel periodicity of Synechococcus populations and grazing by heterotrophic nanoflagellates (HFLAGs) in the bay of Villefranche of the NW Mediterranean are discussed based on analysis of food vacuole contents. Data show that a relationship may exist between vulnerability to predation and average Synechococcus cell size.

A model of iron-light-ammonium colimitation of phytoplankton growth and nitrate uptake is discussed. The model is optimization based with the basic postulate that, when iron is in short supply, that limitation affects ability of cells to acquire carbon and nitrogen. It is also postulated that through evolutionary history phytoplankton have developed ways to partition scarce iron between nitrogen acquisition and carbon acquisition to maximize the rate of growth. Some physiological detail was sacrificed in the model to permit use of the optimality argument.

A question of visibility related to fish and jellies and why some pelagic ecosystems support large stocks of fish while others are dominated by jellyfish is discussed. Two fjords of the same size with quite different pelagic food webs were studied. In one fjord a slightly greater influence of coastal water in the basin water causes the exponential light absorbance coefficient below 100 m to be 2-3 times as high as that in other fjords. Reduction in light flux of several orders of magnitude reduces possibility of visual foraging, but predation in jellyfish is tactile and is not influenced. The visibility regime is decisive.

Dimension effects of enclosures on ecological processes in pelagic systems are discussed based on examination of several characteristics inherent to experimental ecosystems for influence on ecological processes in five cylindrical indoor benthic-pelagic enclosures of different size and shape. It was found, among other findings, that factors that lead to the development of different plankton assemblages can be related to mesocosm geometry and that the ratio of light-receiving surface area-to-water column volume regulates gross primary productivity and the No(2ub.3)(neg) consumption rate. Area-to-folume effects may have substantial influence, but likely can be allowed for to cut down on artifacts of enclosure.

Paleolimnology has provided evidence related to algal responses to pH decline and dissolved organic carbon loss in whole-lake acidification. Fossil pigment analyses and 19 year-long historical records were used for quantification of the response to optical and chemical changes after experimental acidification with three different acids. Pigments from green algae went up by a factor of 2 during acidification with sulfuric acid. Those from cryptophytes were not affected and diatoxanthin from diatoms went down. Complex interactions of pH, dissolved organic carbon (DOC) and light may help to explain the high variability found in the responses to acidification.

In the marine cyanobacterium Prochlorococcus, photophysiology has been studied for the purpose of learning about ecotypic differences among cultured isolates. The bacteria came from varying regions. The hypothesis that Prochlorococcus is made up of genetically distinct ecotypes that taken together expand the range of light intensities the genus can do well in. The isolates, all of which are low-light adapted, fell into two groups based on growth response to light intensity. One group would be unable to grow at all in the light intensities that are optimal for the other group. Physiological differences among ecotypes likely come from differing relative distributions in a given water column and fluctuations in relative abundance because of seasonal changes and stability of water column.

The fading of nine reactive dyes on cotton fabrics under light and perspiration was investigated using the ATTS standard and many factors affecting the stability of these dyes were discussed, viz. Exposure environment, chromophores of dyes, the pH value and components of the artificial perspiration. The experimental results show that reactive dyes exhibit lowest stability under simultaneous exposure to light, perspiration and oxygen in a wet state. Among all selected dyes, Cu-complex azo reactive dyes appear to be the most sensitive, whereas anthraquinone reactive dyes show the best stability. The pH value of perspiration may also greatly influence the fading of dyes by affecting the hydrolytic stability of dye–fibre bonding. Furthermore, the study on the contribution of artificial perspiration components discloses that some acidic components play major roles in the fading of the dyes and inorganic salts usually decelerate the fading extent. [ABSTRACT FROM AUTHOR]

Cherry (Prunus avium L.) saplings were grown under natural sunlight (controls) or moderate shading (up to 30%, depending on the incident light intensity and the hour of the day). Reduced light intensity increased the dry mass of each of the plant components studied. Consequently, the total dry mass of shaded plants was significantly greater than that of controls at the end of the growing season. However, the diurnal trend in the level of photosynthesis (per unit of leaf area) of shaded plants was similar to the controls in August, but lower in September. As the growing season proceeded, reduced photosynthetic rates, thinner mesophyll and larger specific leaf area in the shaded plants indicated that leaf development had adapted to shaded conditions throughout the growing season. It is suggested that increased growth of shaded plants was caused by a higher initial relative growth rate and a greater whole-plant photosynthesis. Shading consistently reduced transpiration over the season, therefore improving water use efficiency of shaded leaves. Our results suggest that a moderate reduction in light intensity can be a useful method for improving growth and saving water in hot and dry environments. [ABSTRACT FROM AUTHOR]

Presents a report on light and its role as a crucial environmental signal. How light is perceived and transduced by at least two principal groups of photoreceptors, phytocrhomes and cryptochromes; Findings that the modulation of physiological responses in plants is achieved by genetic interaction between photoreceptors; Genetic interaction between the Arabidopsis photoreceptors phyB and cry2; Conclusion that the photoreceptors interact in nuclear speckles that are formed in light-dependent fashion.

Light effects and nitrogen cycling rates in a tropical hypereutrophic lake, Lake Maracaibo in Venezuela, are discussed based on surveys of the lake made over the most recent 40 years. They give information about primary production rates. Information about standing stocks of important foodweb organisms, nutrients, salinity, dissolved oxygen, and other water-quality characteristics. It appears that internal recycling provides a major nutrient supply process.

Effects of light and ciliate density on the feeding of Stylophora pistillata, a zooxanthellate coral, on microheterotrophs, including oligotrichous ciliates and bacteria, have been studied. Topics include cultures and labeling of bacteria and ciliates, feeding experiments, and the effect of light.