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Author Radetsky L.; Patel J. S.; Rea M. S.
Title Continuous and Intermittent Light at Night, Using Red and Blue LEDs to Suppress Basil Downy Mildew Sporulation Type Journal Article
Year 2020 Publication HortScience Abbreviated Journal
Volume 55 Issue 4 Pages 483-486
Keywords Animals; Plants
Abstract Lighting from red and blue light-emitting diodes (LEDs) is common for crop production in controlled environments. Continuous application of red or blue light at night has been shown to suppress sporulation by Peronospora belbahrii, the causal organism of basil downy mildew (DM), but the suppressing effects of intermittent applications of red and blue LEDs have not been thoroughly researched. This study examined the effects of red (λmax = 670 nm) and blue (λmax = 458 nm) LED top lighting, at two photosynthetic photon flux densities (PPFD = ≈12 and ≈60 µmol·m−2·s−1), using continuous (10-hour) nighttime and two intermittent nighttime exposures, to suppress basil DM sporulation. The two intermittent treatments consisted of one 4-hour exposure and three 1.3-hour exposures spaced 3 hours apart. Continuous nighttime treatments with blue or red LED top lighting at ≈60 µmol·m−2·s−1 were able to suppress basil DM sporulation by more than 99%. At a given nighttime dose of light that did not completely suppress sporulation, continuous lighting was more effective than intermittent lighting, and for these partially suppressing doses, red LEDs were not significantly different from blue LEDs for suppressing sporulation. The present study showed that horticultural lighting systems using red and blue LEDs to grow crops during the day can also be used at night to suppress basil DM sporulation by up to 100%.
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Call Number UP @ altintas1 @ Serial 3143
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Author Maggi, E.; Bertocci, I.; Benedetti-Cecchi, L.
Title Light pollution enhances temporal variability of photosynthetic activity in mature and developing biofilm Type Journal Article
Year 2020 Publication Hydrobiologia Abbreviated Journal Hydrobiologia
Volume 847 Issue 7 Pages 1793-1802
Keywords Plants; Ecology
Abstract Artificial light at night (ALAN) has been recently recognized as a threat for aquatic systems, but a comprehensive knowledge of its effects is still lacking. A fundamental question is whether and how ALAN might affect temporal variability of communities, thus undermining the stability of mature assemblages or influencing the colonization process. Here we investigated the role of ALAN on temporal variability of total biomass and maximum photosynthetic efficiency of marine autotrophic biofilms colonizing Mediterranean high-shore rock surfaces while controlling for density of their main grazers. Results showed stability in total biomass, but an increase in maximum photosynthetic efficiency from unlit to lit conditions, which suggested a temporal change in composition and/or abundance of different taxa within mature assemblages. The effect was weaker during the colonization process; in this case, density of grazers acted in the opposite direction of ALAN. We suggest that the addition of light at times when it would not be naturally present may affect the temporal variability of a variety of functioning in aquatic systems, depending on species-specific sensitivities to ALAN within microbial assemblages and/or indirect effects mediated by their consumers. We highlight to further investigate the role of this emergent topic in aquatic ecology.
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ISSN 0018-8158 ISBN Medium
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Call Number UP @ altintas1 @ Serial 3146
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Author Haag, C.R.; Riek, M.; Hottinger, J.W.; Pajunen, V.I.; Ebert, D.
Title Genetic diversity and genetic differentiation in Daphnia metapopulations with subpopulations of known age Type Journal Article
Year 2005 Publication Genetics Abbreviated Journal Genetics
Volume 170 Issue 4 Pages 1809-1820
Keywords Plants; Aging; Animals; Daphnia/*genetics/*physiology; *Genetic Variation; *Genetics, Population
Abstract If colonization of empty habitat patches causes genetic bottlenecks, freshly founded, young populations should be genetically less diverse than older ones that may have experienced successive rounds of immigration. This can be studied in metapopulations with subpopulations of known age. We studied allozyme variation in metapopulations of two species of water fleas (Daphnia) in the skerry archipelago of southern Finland. These populations have been monitored since 1982. Screening 49 populations of D. longispina and 77 populations of D. magna, separated by distances of 1.5-2180 m, we found that local genetic diversity increased with population age whereas pairwise differentiation among pools decreased with population age. These patterns persisted even after controlling for several potentially confounding ecological variables, indicating that extinction and recolonization dynamics decrease local genetic diversity and increase genetic differentiation in these metapopulations by causing genetic bottlenecks during colonization. We suggest that the effect of these bottlenecks may be twofold, namely decreasing genetic diversity by random sampling and leading to population-wide inbreeding. Subsequent immigration then may not only introduce new genetic material, but also lead to the production of noninbred hybrids, selection for which may cause immigrant alleles to increase in frequency, thus leading to increased genetic diversity in older populations.
Address Unite d'Ecologie et d'Evolution, Departement de Biologie, Universite de Fribourg, CH-1700 Fribourg, Switzerland. christoph.haag@ed.ac.uk
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ISSN 0016-6731 ISBN Medium
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Notes (up) PMID:15937138; PMCID:PMC1449778 Approved no
Call Number LoNNe @ kagoburian @ Serial 660
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Author Bunning, E.; Moser, I.
Title Interference of moonlight with the photoperiodic measurement of time by plants, and their adaptive reaction Type Journal Article
Year 1969 Publication Proceedings of the National Academy of Sciences of the United States of America Abbreviated Journal Proc Natl Acad Sci U S A
Volume 62 Issue 4 Pages 1018-1022
Keywords Plants; Moonlight
Abstract Threshold values of photoperiodic time-measurements correspond approximately to moonlight intensities. Experiments with Glycine and Euglena reveal that this is also the threshold value for synchronization of the circadian cycle. Saturation of this reaction is reached with 10 lx in 12:12 hr light-dark cycles. Thus, moonlight might disturb time measurement.In Glycine, Arachis, and Trifolium the intensity of the light coming from the moon to the upper surface of the leaf is reduced by circadian leaf movement to values between 5 and 20 per cent (or even less than 5 per cent) of full-moon light intensity. Such a reduction eliminates the disturbing effects of moonlight. This finding indicates that leaf movements have an adaptive value of the kind that Darwin sought to identify. It also indicates that the behavior of the upper leaf epidermis as a “sense organ for light”(13) has an adaptive value.In the short-day plants Perilla ocymoides and Chenopodium amaranticolor, a specific photoperiodic phenomenon was found that counteracts the disturbing effect of moonlight. Here light intensities similar to those of moonlight, introduced during the night, promote flowering instead of inhibiting it.
Address Institute Of Biology, University Of Tubingen, Germany
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ISSN 0027-8424 ISBN Medium
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Notes (up) PMID:16591742; PMCID:PMC223607 Approved no
Call Number GFZ @ kyba @ Serial 3035
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Author Raven, J.A.; Cockell, C.S.
Title Influence on photosynthesis of starlight, moonlight, planetlight, and light pollution (reflections on photosynthetically active radiation in the universe) Type Journal Article
Year 2006 Publication Astrobiology Abbreviated Journal Astrobiology
Volume 6 Issue 4 Pages 668-675
Keywords Plants
Abstract Photosynthesis on Earth can occur in a diversity of organisms in the photosynthetically active radiation (PAR) range of 10 nmol of photons m(-2) s(-1) to 8 mmol of photons m(-2) s(-1). Similar considerations would probably apply to photosynthetic organisms on Earth-like planets (ELPs) in the continuously habitable zone of other stars. On Earth, starlight PAR is inadequate for photosynthetically supported growth. An increase in starlight even to reach the minimum theoretical levels to allow for photosynthesis would require a universe that was approximately ten million times older, or with a ten million times greater density of stars, than is the case for the present universe. Photosynthesis on an ELP using PAR reflected from a natural satellite with the same size as our Moon, but at the Roche limit, could support a low rate of photosynthesis at full Moon. Photosynthesis on an ELP-like satellite of a Jupiter-sized planet using light reflected from the planet could be almost 1% of the rate in full sunlight on Earth when the planet was full. These potential contributions to photosynthesis require that the contribution is compared with the rate of photosynthesis driven by direct radiation from the star. Light pollution on Earth only energizes photosynthesis by organisms that are very close to the light source. However, effects of light pollution on photosynthesis can be more widespread if the photosynthetic canopy is retained for more of the year, caused by effects on photoperiodism, with implications for the influence of civilizations on photosynthesis.
Address Plant Research Unit, University of Dundee at SCRI, Scottish Crop Research Institute, Invergowrie, Dundee, United Kingdom
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ISSN 1557-8070 ISBN Medium
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Notes (up) PMID:16916290 Approved no
Call Number LoNNe @ christopher.kyba @ Serial 1198
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