Physiological performance of a foliose macrolichen Umbilicaria antarctica as affected by supplemental UV-B treatment

2015 ◽  
Vol 5 (2) ◽  
pp. 222-229 ◽  
Author(s):  
Mariana Gonzalez Medina ◽  
Roxana Avalos-Chacon
Keyword(s):  
Chlorophyll Fluorescence ◽  
High Resistance ◽  
Photosynthetically Active Radiation ◽  
High Intensity ◽  
Photosynthetic Efficiency ◽  
Photosynthetic Apparatus ◽  
Ps Ii ◽  
Fluorescence Kinetics ◽  
Active Radiation ◽  
High Doses

To date, a limited knowledge is available about Umbilicaria antarctica responses when it is exposed high doses of UV-B radiation. It is well established that resistance of Antarctic lichens to natural UV-B levels including increased doses during ozone hole period is high, thanks to numerous photoprotective mechanism. Capacity of the photoprotective processes, however, is not well known This study attempts to determine changes on the photosynthetic efficiency and on the synthesis of UV-B absorbing compounds of U. antarctica when exposed to low photosynthetically active radiation and extremely high intensity of UV-B light: 3.0 W m-2, of UV-B for 3 hours, 6 hours and 7 days. During the experiment, chlorophyll fluorescence was measured to evaluate changes in photosynthetic apparatus of intrathalline alga. After 7 d exposition, amount of UV-B absorbing compounds was evaluated in U. antarctica. Heavy UV-B stress let to an increase in chlorophyll fluorescence kinetics (OJIPs), however, majority of parameters related to functioning of PS II remained unchanged indicating high resistance of U. antarctica to UV-B stress. Potential (FV/FM) and actual (ФPSII) yields of PS II were not affected by the UV-B treatment as well. In majority of cases, heavy UV-B treatment led to a decrease in the amount of UV-B absorbing compounds extracted from treated thalli.

scholarly journals Chlorophyll Fluorescence Kinetics May Be Useful to Identify Early Drought and Irrigation Effects on Photosynthetic Apparatus in Field-Grown Wheat

Agronomy ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1275
Author(s):  
Lenka Botyanszka ◽  
Marek Zivcak ◽  
Erik Chovancek ◽  
Oksana Sytar ◽  
Viliam Barek ◽  
...  
Keyword(s):  
Chlorophyll Fluorescence ◽  
Water Deficit ◽  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Photosynthetic Apparatus ◽  
Optical Methods ◽  
Accurate Information ◽  
Ojip Transient ◽  
Fluorescence Kinetics ◽  
Non Invasive

To assess the reliability and sensitivity of non-invasive optical methods to detect the early effects of water deficit in the field, we analyzed the time-series of non-invasive measurements obtained in a dry season in a representative collection of wheat genotypes grown in small-plot field trials, in non-irrigated and irrigated variants. Despite a progressive water deficit and significant yield loss, the measurements indicated very minor changes in chlorophyll content or canopy cover. This corresponded well to the insignificant differences in spectral reflectance normalized difference vegetation index (NDVI) values. On the other hand, we identified the significant and rapid response of fast fluorescence kinetics data following the onset of irrigation. Analysis of parameters showed the main effects of drought were associated with changes in the amplitude of the I–P phase of the OJIP transient, indicating changes at the level of photosystem I and beyond. Statistical analyses identified the integrative parameter performance index PItot as the most sensitive parameter, which well-reflects the differences in responses of the genotypes to water deficit. Our results suggest that focusing on photosynthetic functions detected by the rapid chlorophyll fluorescence records can provide more accurate information on the drought stress level, compared to the structural data obtained by absorbance or reflectance measurements.

Initial Investigations of a Shallow-Layer Algal Production System

1979 ◽  
Author(s):  
L. P. Raymond
Keyword(s):  
Photosynthetically Active Radiation ◽  
Phaeodactylum Tricornutum ◽  
Photosynthetic Efficiency ◽  
Culture Media ◽  
Marine Diatom ◽  
Foam Fractionation ◽  
Total Solar Radiation ◽  
Full Potential ◽  
Active Radiation ◽  
Bio Engineering

A system for the intensive cultivation of the marine diatom Phaeodactylum tricornutum is described and evaluated. Unique features of the system include: (a) the incorporation of solar heat collection device which transmits only photosynthetically active radiation (PAR) to the growing culture; (b) the formulation of a new seawater enrichment medium that promotes physiological responses not previously observed in culture; and (c) the use of a foam fractionation device which separates microalgae, from the culture media, adds CO2-enriched air, and/or simultaneously recirculates the growing culture in shallow layers through an interconnecting series of hemicylindrical channels. The outdoor system demonstrated that very high ash-free dry weight yields of Phaeodactylum tricornutum are produced, a result of high photosynthetic efficiency. Actual yield over an eight-day period was equivalent to 39.57 ash-free dry tons/acre-year. Observed photosynthetic efficiency, based on photosynthetically active radiation incident upon the external surface of the system, is 13.1 percent, nearly three times the limit previously considered economically practical. The data indicate that greater yields may be expected using this system at locations receiveing higher insolation. A conservative projection is that 80 ash-free dry tons/acre-year will be realized in land regions receiveing 3 × 1010 Btu/acre-year total solar radiation. It is concluded that this system clearly warrants further investigation to determine its capacity to produce large and economical quantities of algal biomass for use as potential petroleum-fuel substitutes. The development of a comprehensive and systematic bio-engineering program is recommended to upgrade and evaluate the system to its full potential.

Photosynthetic Utilisation of Lightflecks by Understory Plants

1988 ◽  
Vol 15 (2) ◽  
pp. 223 ◽  
Author(s):  
RW Pearcy
Keyword(s):  
Photosynthetically Active Radiation ◽  
Co2 Fixation ◽  
Photosynthetic Apparatus ◽  
Continuous Light ◽  
Stomatal Opening ◽  
Carbon Gain ◽  
Light Activation ◽  
Low Light ◽  
Active Radiation ◽  
Induction State

The light environment in forest understories is highly dynamic because the weak shade light is period- ically punctuated by lightflecks lasting from a second or less to tens of minutes. Although present for only a small fraction of the day, these lightflecks can contribute more than two-thirds of the photosynthetically active radiation. Several factots are of importance in determining the capacity of a leaf to utilise lightflecks. Following long low-light periods the induction state of the photosynthetic apparatus is limiting. During induction, 20-60 min may be required before maximum assimilation rates are reached due first to a light activation requirement. of ribulose-1,5-bisphosphate carboxylasel oxygenase and later to the light-induced stomatal opening. Continuous light is not required and induction occurring during a series of lightflecks results in higher carbon gain for later as compared to earlier lightflecks. Post-illumination CO2 fixation resulting from utilisation of metabolite pools built up during the lightfleck can significantly enhance carbon gain during short (5-20 s) lightflecks. The carbon gain of a leaf in response to a lightfleck is a consequence of the limitations imposed by induction state plus the enhancements due to post-illumination CO2 fixation. In the field, this will depend on the frequency and duration of the lightflecks and the duration of the intervening low-light periods.

scholarly journals Plant Fluorescence Measured under Two Extreme Lighting Conditions Using a Passive Spectroradiometer

2017 ◽  
Author(s):  
Trina Merrick ◽  
Ralf Bennartz ◽  
Maria Luisa S. P. Jorge ◽  
Thiago S. F. Silva ◽  
John Rausch ◽  
...  
Keyword(s):  
Chlorophyll Fluorescence ◽  
Photosynthetically Active Radiation ◽  
Light Emitting Diode ◽  
Fluorescence Yield ◽  
Spectral Measurements ◽  
Light Emitting ◽  
Active Radiation ◽  
Lighting Conditions ◽  
Margin Of Error ◽  
Absorbed Photosynthetically Active Radiation

In this study, we evaluated chlorophyll fluorescence (CF) under two extreme illumination conditions at plant scale with a passive spectroradiometer. Fluorescence (F) was estimated by reading directly from radiance spectra of a variety of plants illuminated with light-emitting diode (LED) grow lights in the laboratory. Solar-induced fluorescence (SIF) was estimated from spectral measurements of the same plants under sunlight using the Fraunhofer Line Depth (FLD) method. Chlorophyll fluorescence yield (Fyield) and solar-induced fluorescence yield (SIFyield) were calculated by normalizing F and SIF with absorbed photosynthetically active radiation (APAR). Two approaches to estimating APAR were compared: utilizing white reference spectra and reflected spectra versus white reference spectra combined with the fraction of absorbed photosynthetically active radiation (fPAR) derived from literature. Average F and SIF were different by a factor of approximately twenty-four (F = 0.110 ± 0.038 Wm−2μm−1sr−1 versus SIF = 2.60 ± 1.87 Wm−2μm−1sr−1). In contrast, the average normalized values Fyield and SIFyield were within the margin of error of one another (Fyield = 0.022 ± 0.008 μm−1sr−1 and SIFyield = 0.030 ± 0.020 μm−1sr−1). This study highlights the influence of APAR on CF and the importance of properly accounting for it when estimating yield and demonstrates the ability of two simple and portable experimental setups with a passive instrument to obtain fluorescence metrics.

Oxygen evolution rate in Antarctic filamentous alga Stigeoclonium sp. evaluated by optodes relates to chlorophyll fluorescence parameters (Short Communication)

2018 ◽  
Vol 8 (1) ◽  
pp. 143-150
Author(s):  
Peter Váczi
Keyword(s):  
Chlorophyll Fluorescence ◽  
Linear Relationship ◽  
Oxygen Evolution ◽  
Photosynthetically Active Radiation ◽  
Filamentous Alga ◽  
Evolution Rate ◽  
O2 Evolution ◽  
Effective Quantum Yield ◽  
Active Radiation ◽  
Oxygen Evolution Rate

Photosynthetic reactions of algal communities, the essential component of primary production in polar regions, are strongly dependent on environmental factors. Among them, availability and amount of light in particular parts of growing season are of major importance. In this paper, the response of the photosynthetic processes of a filamentous fresh-water alga to photosynthetically active radiation (PAR) was studied by two approaches. The simultaneous measurements of the effective quantum yield (FPSII) and oxygen evolution rate (OER) at stepwise increasing photosynthetically active radiation provided data for beneficial correlation analysis of the FPSII to OER relationship in a wide range of PAR. In this study, the culture of filamentous alga Stigeoclonium sp. was analyzed. The linear relationship between FPSII and OER was found for the low PAR (the range of 0 – 200 mmol.m-2.s-1). At high PAR levels (200 – 1000 mmol.m-2.s-1) another linear relationship with different slope was found. The approach combining the fluorometric and oxymetric method might be used for calibration of data in follow up studies and, consequently for evaluation of photosynthetic rates (O2 evolution) from chlorophyll fluorescence data.

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