Indagine sugli effetti provocati da un eccesso di radiazione UV-B su foglie di Populus Alba L. mediante miscrospettrofluorimetria e microimaging di fluorescenza

.Foglie di Populus Alba L. (pioppo bianco) sottoposte a trattamento UV-B (280 nm < ? < 315 nm) sono state analizzate mediante tecniche di microscopia a trasmissione, di microspettrofluorimetria e di microimaging di fluorescenza e confrontate con analoghe foglie di controllo prelevate da piante mantenute a livelli standard di irraggiamento. I campioni fogliari impiegati per l\u27esperimento sono stati prelevati a partire dal quindicesimo giorno di accrescimento da piante fatte sviluppare in vivaio. Il trattamento UV (12 h al giorno) realizzato in camera di crescita si ? protratto per un massimo di 7 giorni a partire dal quindicesimo giorno di accrescimento. La radiazione UV-B applicata aveva una densit? di energia pari a 0.15 Wm-2 stimata con uno spettroradiometro a scansione SUV 100 (Biospherical Instruments, San Diego, CA). La strumentazione impiegata per le misure consisteva in un microscopio invertito a epifluorescenza (Diaphoto, Nikon, Japan) equipaggiato con una lampada a mercurio e filtri interferenziali di 10 nm (Andover Corporation, Salem, NH), dotato di ruota portafiltri e CCD per l\u27acquisizione delle immagini di fluorescenza. L\u27analisi dei dati ottenuti durante il periodo di trattamento si articola in tre punti principali: 1)studio delle modificazioni cellulari 2)analisi delle caratteristiche di fluorescenza 3)analisi dei valori di intensit? di fluorescenza a tempi crescenti di trattamento

In situ assessment of quality-related compounds in fruits by using fluorescence sensors

Fruit quality compounds, such as antioxidant phenolics and chlorophyll, were assessed in situ by using a fluorescence method applied by a portable sensor. Indices of anthocyanins (ANTH) and flavonols (FLAV) localized on the fruit surface were obtained based on their screening of chlorophyll fluorescence excitation. The chlorophyll content was estimated by the far red to red chlorophyll fluorescence ratio (CHL index), due to the partial reabsorption of red fluorescence by chlorophyll itself. In kiwifruits, the CHL index was found to be well linearly correlated to the chlorophyll content determined by wet chemistry on the same fruit samples. Full sunlight exposed kiwifruits possessed a higher content of chlorophyll than shaded kiwifruits. This is an important parameter to know for assessing fruit quality and storability. Based on the estimation of the red-pigmented anthocyanins, we defined a new rapid method to determine the maturity level of olives after harvest, giving the proportion of red and green olives, important for the quality of the olive oil produced. In plums, ANTH and FLAV were found to be linearly correlated to the actual content of compounds measured by HPLC analysis of skin extracts. These indices can be, therefore, used to predict the phenolic antioxidant potential of plums and to define their maturity stage

In vivo real-time recording of UV-induced changes in the autofluorescence of a melanin-containing fungus using a micro-spectrofluorimeter and a low-cost webcam.

An optical epifluorescence microscope, coupled to a CCD camera, a standard webcam and a microspectrofluorimeter, are used to record in vivo real-time changes in the autofluorescence of spores and hyphae in Aspergillus niger, a fungus containing melanin, while exposed to UV irradiation. The results point out major changes in both signal intensity and the spectral shape of the autofluorescence signal after only few minutes of exposure, and can contribute to the interpretation of data obtained with other fluorescence techniques, including those, such as GPF labeling, in which endogenous fluorophores constitute a major disturbance

Radiação solar e susceptibilidade da videira à Plasmopara Viticola

A radiação solar exerce papel importante no desenvolvimento de algumas doenças fúngicas, devido à sua ação direta sobre os microorganismos e também devido ao seu efeito indireto sobre a produção de compostos específicos nas plantas. Este experimento examinou o efeito de dois ambientes de luz (100% e 35% da intensidade máxima) sobre o conteúdo de polifenóis nas folhas da videira e quantificou sua relação com a resistência ao míldio (Plasmopara viticola). As concentrações de polifenóis na epiderme das folhas foram quantificadas de forma não destrutiva, durante a estação de crescimento de 2006, usando o equipamento portátil Dualex, baseado na fluorescência da clorofila. O delineamento experimental consistiu de seis parcelas de 30 videiras e as medidas foram feitas nas 12 plantas centrais. As folhas foram inoculadas com uma suspensão de esporângios com 50.000 esporos de P. viticola por mL e a intensidade da doença foi avaliada depois do aparecimento dos primeiros sintomas. As folhas das plantas mantidas à plena luz solar apresentaram alta concentração de polifenóis e severidade da doença significativamente menor do que as folhas das plantas mantidas sob a tela de sombreamento. Estes resultados indicam uma relação inversa entre os polifenóis produzidos pelas folhas da videira e a severidade do míldio.Solar radiation plays an important role in the development of some fungal diseases due to its direct action on the microorganisms and also its indirect effect on the production of specific plant compounds. This experiment examined the effect of two light environments (100% and 35% of full strength) on the polyphenolic content of grapevine leaves and quantified their relation to resistance to downy mildew (Plasmopara viticola). Leaf epidermal polyphenolic contents were non-destructively measured during the growing season 2006 using the Dualex chlorophyll fluorescence-based portable leaf-clip. The experimental design consisted of six parcels of 30 vines and measurements were performed on the 12 central vines. The leaves were inoculated with a sporangia suspension containing 50,000 sporangia of P. viticola per mL and the disease severity was assessed after the appearance of symptoms. Leaves maintained at 100% sun had high polyphenolic content and significantly lower disease severity compared to leaves under shading nets. These results indicate an inverse relationship between produced polyphenolics and downy mildew severity

UV radiation promotes flavonoid biosynthesis, while negatively affecting the biosynthesis and de-epoxidation of xanthophylls: consequence for photoprotection?

There is evidence that UV radiation may detrimentally affect the biosynthesis of carotenoids, particularly de-epoxided xanthophylls, while strongly promoting phenylpropanoid, particularly flavonoid biosynthesis in a range of taxa. Here we tested the hypothesis that mesophyll flavonoids might protect chloroplasts from UV-induced photo-oxidative damage, by partially compensating for the UV-induced depression of xanthophyll biosynthesis. To test this hypothesis we grew two members of the Oleaceae family, Ligustrum vulgare L. and Phillyrea latifolia L., under either partial shading or fully exposed to sunlight, in the presence or in the absence of UV radiation. The examined species, which display very similar flavonoid composition, largely differ in their ability to limit the transmission of UV and visible light through the leaf and, hence, in the accumulation of flavonoids in mesophyll cells. We conducted measurements of photosynthesis, chlorophyll a fluorescence kinetics, the concentrations of individual carotenoids and phenylpropanoids at the level of whole-leaf, as well as the content of epidermal flavonoids. We also performed multispectral fluorescence micro-imaging to unveil the intra-cellular distribution of flavonoids in mesophyll cells. UV radiation decreased the concentration of carotenoids, particularly of xanthophylls, while greatly promoting the accumulation of flavonoids in palisade parenchyma cells. These effects were much greater in L. vulgare than in P. latifolia. UV radiation significantly inhibited the de-epoxidation of xanthophyll cycle pigments, while enhancing the concentration of luteolin, and particularly of quercetin glycosides. Flavonoids accumulated in the vacuole and the chloroplasts in palisade cells proximal to the adaxial epidermis. We hypothesize that flavonoids might complement the photo-protective functions of xanthophylls in the chloroplasts of mesophyll cells exposed to the greatest doses of UV radiation. However, UV radiation might result in adaxial mesophyll cells being less effective in dissipating the excess of radiant energy, e.g., by decreasing their capacity of thermal dissipation of excess visible light in the chloroplast

The use of red species for urban “greening” in the age of climate change

The red/purple colour of some plant species is due to the presence of anthocyanins, a colourful class of flavonoids widely spread in the Plantae kingdom. Beside a doubtless aesthetic value of anthocyanin-rich species, the presence of these pigments confers them peculiar physiological and biochemical properties which make red species usually more tolerant to some environmental stresses, as occur in Mediterranean area. The ability of anthocyanins to partially absorb a proportion of light striking the mesophyll (mainly green and yellow wavebands) represents a useful feature against a condition of excessive light which not only occurs when plants are subjected to high irradiances, but also when other stressors (e.g., high temperature, low water availability) impair the photosynthetic process. The work elucidates as the presence of anthocyanins determines morpho-anatomical, biochemical and physiological effects. In particular, the roles of these pigments are described comparing the leaf ontogenesis of two genotypes of Prunus cerasifera, one with red (var. Pissardii) and one with green leaves (clone 29C). Red-leafed Prunus resulted better protected, especially during the leaf senescence. The presence of anthocyanins also promotes a delayed leaf senescence (4-week-longer leaf lifespan) which is a well-appreciated feature in the context of urban “greening”

Assessing the response of plant flavonoids to UV radiation : an overview of appropriate techniques

Flavonoids are a large group of plant secondary metabolites that are present in most plants, and are vital for plant growth, development and protection. Among the many functions of these compounds is their contribution to stress amelioration. The accurate identification and quantification of total or individual flavonoids in plants exposed to stressful conditions (e.g. ultraviolet radiation) is challenging due to their structural diversity. The present review provides the up to date knowledge and highlights trends in plant flavonoid analysis. The review covers all steps from the field to the laboratory, focussing on UV-B effects on flavonoids, and identifying critical issues concerning sample collection, pre-treatment, extraction techniques and quantitative or qualitative analysis. A well-planned sampling and sample prehandling strategy is vital when capturing organ, tissue and developmental-stage dependent changes in flavonoids, as well as the dynamic changes due to time of UV-exposure and diurnal or seasonal parameters. A range of advanced extraction and purification techniques can facilitate the quantitative transfer of flavonoids to solvents. The advantages and disadvantages of analytical methods, including chromogenic assays, liquid and thin-layer chromatography, mass spectrometry, nuclear magnetic resonance detection, and non-destructive in situ fluorescent analysis need to be consciously evaluated in the context of the specific biological question posed. Thus, no one method can be applied to every single study of flavonoid. The message of this review is that researchers will need to carefully consider the biological process that they intend to study, and select an analytical method that optimally matches their specific objectives.Peer reviewe