Search results for "a fluorescence"
showing 10 items of 19 documents
In vivo photoprotection mechanisms observed from leaf spectral absorbance changes showing VIS–NIR slow-induced conformational pigment bed changes
2019
Abstract Regulated heat dissipation under excessive light comprises a complexity of mechanisms, whereby the supramolecular light-harvesting pigment–protein complex (LHC) shifts state from light harvesting towards heat dissipation, quenching the excess of photo-induced excitation energy in a non-photochemical way. Based on whole-leaf spectroscopy measuring upward and downward spectral radiance fluxes, we studied spectrally contiguous (hyperspectral) transient time series of absorbance A(λ,t) and passively induced chlorophyll fluorescence F(λ,t) dynamics of intact leaves in the visible and near-infrared wavelengths (VIS–NIR, 400–800 nm) after sudden strong natural-like illumination exposure. …
Leaf-Level Spectral Fluorescence Measurements : Comparing Methodologies for Broadleaves and Needles
2019
Successful measurements of chlorophyll fluorescence (ChlF) spectral properties (typically in the wavelength range of 650–850 nm) across plant species, environmental conditions, and stress levels are a first step towards establishing a quantitative link between solar-induced chlorophyll fluorescence (SIF), which can only be measured at discrete ChlF spectral bands, and photosynthetic functionality. Despite its importance and significance, the various methodologies for the estimation of leaf-level ChlF spectral properties have not yet been compared, especially when applied to leaves with complex morphology, such as needles. Here we present, to the best of our knowledge, a first comparison of …
Physiological Performance of a Coastal Marsh Plant Hydrocotyle vulgaris in Natural Conditions in Relation to Mineral Nutrition and Mycorrhizal Symbio…
2020
Abstract Fluctuating soil salinity and competition for light are the main factors affecting plant distribution and performance in coastal salt marshes. The aim of the present study was to assess plant performance by means of non-destructive instrumental methods in a highly heterogeneous natural habitat. More specifically, environmental factors affecting growth and physiological performance of a clonal plant Hydrocotyle vulgaris L. were investigated. Changes in soil salinity, soil mineral characteristics, leaf nutrient concentrations, morphological parameters, chlorophyll fluorescence, and mycorrhizal symbiosis were analysed in different experimental plots of naturally growing H. vulgaris pl…
Relationship Between Functional Traits, Functional Types, and Habitat in Boreonemoral Bryophytes
2020
Abstract The aim of the present study was to determine a relationship between physiological traits and functional types of bryophytes from five boreonemoral habitats with a particular emphasis on discriminative ability of these traits. Sampling of 25 species was performed four times during one season. Water content, chlorophyll a fluorescence and photosynthetic pigment concentration were measured in field and water-equilibrated samples. Principal component analysis indicated the existence of an inverse relationship between concentration of pigments and water content. Linear discriminant analysis showed that relatively high mean predicted posterior probabilities of correct classification of …
The application protocol impacts the effectiveness of biocides against lichens
2020
Abstract This work analyzed the influence of different application protocols on the efficacy of two biocides against the foliose lichen Xanthoparmelia tinctina on the sandstones of the Roman Archaeological site of Luni (Italy). The hypotheses that (a) biocide application tools (brush vs. poultice), (b) pre-treatment hydration, and (c) post-treatment washing may affect devitalization success were verified by monitoring chlorophyll a fluorescence of thalli, both in situ and in laboratory conditions. The hypothesis that (d) stone substrate may act as reservoir for later biocide release under repeated cycles of wetting and drying was also assayed. Analyses confirmed the importance of the applic…
Species- and site-specific efficacy of commercial biocides and application solvents against lichens
2017
Abstract Control of lichens on stone cultural heritage is mostly achieved by a combination of mechanical removal with biocide applications. However, there is a lack of scientific evidence on the efficacy of different biocides on different species, and on the consistency of biocide effects on heritage sites in different environmental conditions. This results in some uncertainty when conservation interventions to control lichens are routinely defined on the basis of restoration tradition or empirical evaluation, without experimental measures of how lichens respond. In this work, we quantitatively evaluated (a) the efficacy of five commercially-available biocides, applied using a brush or with…
85Rb D1 pāreju Fg=2 – Fe=3 un Fg=2 – Fe=2 lāzerinducētās fluorescences cirkulāro komponenšu atkarības no ārējā magnētiskā lauka eksperimentāli pētīju…
2019
Šī darba mērķis bija izpētīt lāzerinducētas fluorescences (LIF) signāla struktūras pie mainīga ārējā magnētiskā lauka rubīdija atomāro tvaiku šūnā. Tas tika paveikts novērojot divas pretēji cirkulāri polarizētas LIF gaismas komponentes. Šim darbam tika izvēlētas 85Rb D1 līnijas Fg=2→Fe =3 un Fg=2→Fe =2 pārejas un tika sasniegtas magnētiskā lauka vērtības līdz 3000 Gausiem. Tika pētīta lāzera stara jaudas un izvēlētās pārejas ietekme uz LIF signālu, un iegūtie eksperimentālie signāli tika salīdzināti ar Lāzeru Centrā izveidota teorētiskā modeļa datiem [1].
Modeļsistēmas izveide spilvainā ancīša (Agrimonia pilosa) pētījumiem kontrolētos apstākļos par vides faktoru ietekmi uz augu fizioloģisko stāvokli
2021
Darbā ir apkopota informācija par mitruma ietekmi uz augu fizioloģiskajiem parametriem. Darba mērķis bija izveidot spilvainā ancīša Agrimonia pilosa modeļsistēmu kontrolētos apstākļos pētījumiem par vides faktoru ietekmi uz augu fizioloģisko stāvokli. Fizioloģiskās atbildes uz mitruma ietekmi noteica ar hlorofila a fluorescences analīzes palīdzību. Darba rezultātā secināts, ka Agrimonia pilosa augšņu analīžu rezultāti kopumā atbilst vispārpieņemtajiem augiem nepieciešamajām minerālās barošanās prasībām. Eksperimenta laikā izdevās vienmērīgi nodrošināt augsnei nepieciešamo mitruma līmeni pa variantiem. Hlorofila a fluorescence parādīja, ka Agrimonia pilosa augiem vispiemērotākie ir vidēja mi…
Physiological Aspects of Nitrogen Fertilizer Impact on Latvian Origin Cannabis Sativa L .
2015
The aim of the present study was to evaluate nitrogen fertilizer impact on photosynthesis and yield of hemp, applying modern non-destructive methods. The main object of the investigation – hemp cultivar of Latvian origin ‘Pūriņi’. Laboratory and field experiments showed diverse effects of different nitrogen fertilizer doses on various parameters. Additional nitrogen fertilizer dose of 60 kg ha-1 is most effective as evaluated by chlorophyll content in hemp leaves and changes of chlorophyll a fluorescence parameters. Nitrogen fertilizer negatively affected fiber content in hemp stems, therefore while cultivating hemp only for fiber production use of nitrogen fertilizer should be reduced. Acc…
3D digitization of transparent objects by polalization techniques in IR & by triangulation in UV
2011
Two non-conventional methods for the 3D digitization of transparent objects via non-contact measurement are reported in this thesis. 3D digitization is a well acknowledged technique for opaque objects and various commercial solutions based on different measurement approaches are available in the market offering different types of resolution at different prices. Since these techniques require a diffused or lambertian surface, their application to transparent surfaces fails. Indeed, rays reflected by the transparent surface are perturbed by diverse inter-reflections induced by the refractive properties of the object. Therefore, in industrial applications like quality control, the transparent …