Research: UV Radiation, Sunlight

Allen, D., S Nogues and N Baker (1998). “Review article. Ozone depletion and increased UV-B radiation: is there a real threat to photosynthesis?” Journal of Experimental Botany 49(328): 1775- 1788.

This critical review of recent literature questions earlier predictions that photosynthetic productivity of higher plants is vulnerable to increased ultraviolet-B (UV-B) radiation as a result of stratospheric ozone (O3) depletion. Direct UV-B-induced inhibition of photosynthetic competence is observed only at high UV-B irradiances and primarily involves the loss of soluble Calvin cycle enzymes and adaxial stomatal closure in amphistomatous plants. However, even under these extreme UV-B exposures, acclimation (e.g. induction of UV-B absorbing flavonoids) can protect the photosynthetic processes. In plants irradiated with UV-B throughout development a reduction in productivity is usually associated with a reduced ability to intercept light (i.e. smaller leaf area) and not an inhibition of photosynthetic competence. Finally, a review of field experiments utilizing realistic UV-B enhancement is made to evaluate whether the mechanisms involved in UV-Binduced depressions of photosynthesis are likely to impact on the photosynthetic productivity of crops and natural vegetation in the future. Predictions of plant responses to O3 depletion are suspect from square-wave irradiance experiments due to the increased sensitivity of plants to UV-B at relatively low photosynthetically-active photon flux densities (PPFD) and ultraviolet-A (UV-A) irradiances. Realistic modulated UV-B irradiances in the field do not appear to have any significant effects on photosynthetic competence or light-interception. It is concluded that O3 depletion and the concurrent rise in UV-B irradiance is not a direct threat to photosynthetic productivity of crops and natural vegetation.Key words: Biomass, development, ozone depletion, photosynthesis, ultraviolet-B.

 

Bonomelli, A., L. Mercier, J. Franchel, F. Baillieul, E. Benizri, and Marie-Claude Mauro (2004). “Response of Grapevine Defenses to UV—C Exposure.” Am. J. Enol. Vitic 55(1): 51-59.

The defense potential of a tolerant American Vitis rupestris cultivar (Rupestris du Lot) and a susceptible European Vitis vinifera cultivar (Chardonnay) in response to UV-C irradiation was investigated. The expression of eight defense-related genes coding for enzymes of the phenylpropanoid pathway (phenylalanine ammonia lyase and stilbene synthase), the octadecanoid pathway (lipoxygenase), and pathogenesis-related proteins (class I and III chitinases, ß-1,3- glucanase, class 6 pathogenesis-related protein, and class 10 pathogenesis-related protein) was followed by real-time reverse transcription polymerase chain reaction (RT-PCR). Phenolic compound accumulation was monitored by microscopic observation. Accumulation of resveratrol, a major grapevine phytoalexin, was evaluated by HPLC, and chitinase and ß-1,3-glucanase enzyme activities were measured. Both grapevine species responded to UV-C treatment by enhancement of defense mechanisms. Intensity of some defense responses was correlated with tolerance to diseases, as previously described for stilbene accumulation: the tolerant species responded more intensely to UV-C exposure than the susceptible one. UV-C irradiation is a practical and reproducible method for inducing grapevine defense responses and can be useful in determining the defense potential of grapevine cultivars.

 

Chalmers, Y. (2005). “Leaf and Fruit Responses of ‘Riesling’ Grapevines to UV-Radiation in the Field.” International Society for Horticultural Science.

The effects of UV-radiation on grapevine leaf and fruit physiology under field conditions were investigated. Selected portions of the light spectrum (within the UV wavelengths) were attenuated with polyester and di- and tri- acetate films. The entire canopy or parts thereof were covered wit these films during berry development. Berry skin pigment composition was determined using a non-destructive spectrophotoetric technique. There was a strong UV-induced shift towards the formation of red and brown pigment components without affecting the sugar levels. Chlorophyll degradation in the leaves and berry skins occurred more rapidly in the high UV-radiation treatments. Exposure to UV-B radiation increased both the concentration of total bound glycosidic secondary metabolites and phenolics. There were some noticeable effects on the aromatic expression in the resulting wines.

 

Crippen, D. D. J. a. J. C. M. (1986). “The Effects of Sun Exposure on the Compositional Development of Cabernet Sauvignon Berries.” Am. J. Enol. Vitic 37(4): 235-242.

The effects of sunlight on Cabernet Sauvignon fruit clusters were studied in a Napa Valley, California, commercial vineyard. Clusters were chosen from sun-exposed locations and from locations shaded by the grapevine canopy. Selected exposed and shaded clusters on one vine were monitored for air temperature and light flux. Berry samples were collected weekly from anthesis and were analyzed for tartrate, malate, glucose, and fructose by HPLC and for potassium by emission spectroscopy. Berry juice was also analyzed for pH, titratable acidity, and soluble solids content. Data were presented both on a concentration basis (mg/g fresh weight) and on a per berry basis (mg/berry). Sun berries were significantly higher in concentrations of tartrate, malate, glucose, and fructose as shown by analysis of variance. No significant differences were found when expressed on a per berry basis, however. Potassium expressed either as concentration or per berry, pH, titratable acidity, and soluble solids showed no significant differences between sun and shade berries. Berries from the canopy shade were significantly heavier than berries exposed to the sun. The observed differences in concentration were attributed to a higher water content in the berries from shaded clusters.

 

Failla, O., L. Mariani, L. Brancadoro, R. Minelli, A. Scienza, G. Murada, and S. Mancini (2004). “Spatial Distribution of Solar Radiation and Its Effects on Vine Phenology and Grape Ripening in an Alpine Environment.” Am. J. Enol. Vitic 55(2): 128-138.

Climate, soil, and vineyard performance were characterized in the northern Italian alpine valley of Valtellina to develop an ecophysiological model for zoning viticultural aptitude of the district. Based on a representative sample of 54 small, steep-sloped terraced vineyards planted with the late-ripening red cv. Nebbiolo, the model included three-year (1998 to 2000) data sets for phenology, maturity curves, yield, vigor, and grape assays, with appropriate indices to manage these sets. Soils were characterized by pedological description and climate by annual values of potential photosynthetically active radiation (PPAR) and estimated thermal fields expressed as growing degree days (GDD) using base 10°C. PPAR ranged from 2700 to 3200 MJm-2year-1 and GDD ranged from 1100 to 1800. Vineyards showed a 12-day range in phenological timing, with early sites having the highest technological maturity and medium sites having the highest phenolic maturity. Elevation and PPAR were the main environmental factors affecting vine budbreak and bloom date; veraison was also affected by crop load and its interaction with PPAR availability. Technological maturity was affected by elevation; phenolic maturity by crop load, PPAR, and its interaction with crop load and elevation. The highest phenolic maturity was recorded in lowcropping vineyards at low elevation and PPAR.

 

Jansen, M. A. K., V. Gaba, and B.M. Greenberg (1998). “Higher plants and UV-B radiation: balancing damage, repair and acclimation.” Trends in Plant Science 3(4): 131-135.

Although UV-B is a minor component of sunlight, it has a disproportionately damaging effect on higher plants. Ultraviolet-sensitive targets include DNA, proteins and membranes, and these must be protected for normal growth and development. DNA repair and secondary metabolite accumulation during exposure to UV-B have been characterized in considerable detail, but little is known about the recovery of photosynthesis, induction of free-radical scavenging and morphogenic changes. A future challenge is to elucidate how UV-B-exposed plants balance damage, repair, acclimation and adaptation responses in a photobiologically dynamic environment.

 

Keller, M. a. N. T.-M. (2004). DOES UV RADIATION AFFECT WINEGRAPE COMPOSITION? ISHS Acta Horticulturae 640: XXVI International Horticultural Congress: Viticulture – Living with Limitations.

Ultraviolet (UV) radiation is known to influence plant growth, development, morphology, and physiology, but its effects on the fruit composition of grapevines are unknown. Potted ‘Cabernet Sauvignon’ and ‘Chardonnay’ grapevines were grown in Australia under either ambient or reduced (2% of ambient) UV during two conescutive seasons. UV reduction was achieved using diacetate films suspended above the plants. In addition, two nitrogen treatments were applied at bloom in the first season and two water regimes were imposed from fruit set to leaf fall in the second season. Ambient UV reduced early-season shoot growth but stimulated lateral shoot growth later in the season and enhanced root growth. UV had no clear effect on leaf chlorophyll and gas exchange but reduced leaf water content and increased carotenoid and flavonoid concentrations. Flower calyptra contained high concentrations of flavonols, but this UV protection was temporarily lost during cap fall (anthesis), making the flowers vulnerable to UV. The combination of ambient UV and low nitrogen stress resulted in reduced fruit set. Nevertheless, UV failed to influence yield and fruit sugar content. Ambient UV increased the flavonol content in ripening post-veraison berries, but had no effect on anthocyanins and hydroxy-cinnamic acids. The impact of UV on fruit amino acids varied with individual compounds, but was insignificant for the predominant amino acids proline and arginine. Hence, of the fruit composition parameters examined, only flavonols were notably affected by UV radiation. Compared with ‘Chardonnay’, vegetative growth of ‘Cabernet Sauvignon’ was more tolerant, but reproductive growth was more sensitive to UV. In general, low nitrogen stress enhanced the UV effect, but low water stress reduced it.

 

Kliewer, M. W. (1977). “Influence of Temperature, Solar Radiation and Nitrogen on Coloration and Composition of Emperor Grapes.” Am. J. Enol. Vitic 28: 96-103.

Fruit coloration was investigated in Emperor vines grown in pots in sunlit phytotron, lathhouse, and field conditions under various temperature and light regimes in combination with different levels of nitrogen.

At day/night temperatures of 37/32°C no anthocyanins were formed in fruits under either high light (HL; 66.5% sunlight) or low light (LL; 9.5% sunlight), whereas at field temperatures (FT; mean daily temperature 20.3°C), considerable anthocyanins formed under HL (100% sun) or LL (8.9% sun). At 37/32°C, soluble solids in fruits did not increase above 12.9° Brix, whereas at FT, 21° Brix was obtained under HL. The inhibition of anthocyanin formation and sugar accumulation in berries at 37/32°C and HL could not be reversed by transferring vines to temperature favorable for anthocyanin synthesis (FT), whereas when vines at 37/32°C and LL were transferred to FT at HL there was rapid accumulation of sugars but only slight formation of anthocyanin. Anthocyanin in berries decreased 59% in 20 days when the vines were transferred from FT-HL to 37/32°C-HL. Anthocyanin and soluble solids were significantly greater (P<0.01) in fruits ripened under FT-HL than under FT-LL. Anthocyanin and soluble solids were significantly less (P<0.05) in berries that received 15% sunlight than 54 or 100% sunlight. Anthocyanin formation did not occur in the complete absence of light, whereas °Brix did not differ significantly between 15%, 3%, and 0% sunlight.

Fruit color and soluble solids were significantly less (P<0.05) and arginine and total free amino acids greater with high levels of nitrogen fertilization than with low levels. The reduced fruit coloration at high nitrogen fertility conditions was attributed mainly to reduction in carbohydrate accumulation and an increase in nitrogenous substances stored in fruits.

 

Kolb, C. A., J. Kopecký, M. Riederer and E E. Pfündel “UV screening by phenolics in berries of grapevine (Vitis vinifera).” Functional Plant Biology 30(12): 1177-1186.

The role of phenolics in UV-screening was investigated in berries of a white grape cultivar (Vitis vinifera L. cv. Bacchus). Fluorescence microscopy revealed accumulation of phenolics in the skin of berries and, by high performance liquid chromatography and mass spectrometry, flavonols and hydroxycinnamic acids were identified as the main groups of UV-absorbing phenolics. Relationships between natural radiation and the synthesis of phenolics were studied in plants that were cultivated in the absence of UV radiation in a greenhouse before outdoor exposure to three different light regimes: the entire solar spectrum, the solar spectrum minus UV-B radiation and only visible radiation. During six days of exposure, flavonol synthesis was significantly stimulated by natural UV, in particular UV-B, but concentrations of hydroxycinnamic acids decreased under all conditions. Direct comparison of fluorimetrically-determined skin absorbance with absorbance of extracted flavonols or hydroxycinnamic acids suggested that acclimation of UV screening depends almost exclusively on flavonol synthesis. While increased flavonol levels resulted in efficient UV-A shielding, UV-B shielding was incomplete, probably due to decreased levels of the UV-B-absorbing hydroxycinnamic acids during exposure.

 

Kolb, C. A., M.A. Kaser, J. Kopecky, G. Zotz, M. Riederer, and E.E. Pfundel (2001). “Effects of natural intensities of visible and ultraviolet radiation on epidermal ultraviolet screening and photosynthesis in grape leaves.” Plant Physiology 127(3): 863-875.

Grape (Vitis vinifera cv Silvaner) vine plants were cultivated under shaded conditions in the absence of ultraviolet (UV) radiation in a greenhouse, and subsequently placed outdoors under three different light regimes for 7 d. Different light regimes were produced by filters transmitting natural radiation, or screening out the UV-B (280-315 nm), or screening out the UV-A (315-400 nm) and the UV-B spectral range. During exposure, synthesis of UV-screening phenolics in leaves was quantified using HPLC: All treatments increased concentrations of hydroxycinnamic acids but the rise was highest, reaching 230% of the initial value, when UV radiation was absent. In contrast, UV-B radiation specifically increased flavonoid concentrations resulting in more than a 10-fold increase. Transmittance in the UV of all extracted phenolics was lower than epidermal UV transmittance determined fluorimetrically, and the two parameters were curvilinearly related. It is suggested that curvilinearity results from different absorption properties of the homogeneously dissolved phenolics in extracts and of the non-homogeneous distribution of phenolics in the epidermis. UV-B-dependent inhibition of maximum photochemical yield of photosystem II (PSII), measured as variable fluorescence of dark-adapted leaves, recovered in parallel to the buildup of epidermal screening for UV-B radiation, suggesting that PSII is protected against UV-B damage by epidermal screening. However, UV-B inhibition of CO(2) assimilation rates was not diminished by efficient UV-B screening. We propose that protection of UV-B inactivation of PSII is observed because preceding damage is efficiently repaired while those factors determining UV-B inhibition of CO(2) assimilation recover more slowly.

 

Kolb, C. A. a. E. E. P. (2005). “Origins of non-linear and dissimilar relationships between epiderman UV absorbance and UV absorbance of extracted phenoloics in leaves of grapevine and barley.” Plant, Cell and Environment 28(5): 580 – 590.

A recent review of climate patterns in Sourthern Germany has suggested significant increases in Ultraviolet (UV) radiation due to decreases in cloud coverage and in cloud frequency which compound the effects of stratospheric ozone depletion. Whether such UV radiation increases result in UV damage of higher plant leaves depends partly on the capacity of UVabsorbing hydroxycinnamic acids and flavonoids located in the plant epidermis to screen out UV radiaiton. Epiderman UV screening is most often assessed from UV absorbance of whole-leaf extracts but in the present work, this method is critically examined. In grapevine (Vitis vinifera L.), hydroxycinnamic acid as well as mono-hydroxylated and orthodihydroxylated flavonoid concentrations increased in parallel with flurometrically detected adaxial epidermal UV absorbance but only the latter class of flavonoid was associated with epidermal UV absorbance in barley (Hordeum vulgare L). For both species, curvilinear relationships between epidermal and total phenolic UV absorbance were established: initial slopes of the curves differed markedly between species. Modelling suggested that curvilinearity arises from UV-transparent epidermal areas located between vacuoles which are particularly UV-absorbind due to high levels of phenolics. The species-dependent differences were related to allocation of high amounts of phenolics in the mesophyll and abazial epidermis in barley but not in grapevine. Both factors, optical heterogeneity and variable distribution of phenolics, severely restrict the use of phenolic absorbance to estimate true epidermal screening.

 

Lafontaine, M., H.R. Schultz, C. Lopes, B. Bálo, and G. Varadi (2005). Leaf and fruit Responses of ‘Riesling’ Grapevines to UV-Radiation in the Field. International Society for Horticultural Science.

Grapevine plants (Vitis vinifera L. cv. Silvaner) were cultivated under shaded conditions in the absence of UV radiation in a greenhouse, and subsequently placed outdoors under filters transmitting natural radiation, or screening out the UV-B (280 to 315 nm), or screening out the UVA (315 to 400 nm) and the UV-B spectral range. All conditions decreased maximum chlorophyll fluorescence (FM) and increased minimum chlorophyll fluorescence (F0) from dark-adapted leaves; however, with increasing UV, FM quenching was stimulated but increases in F0 were reduced. The FV/FM ratio (where FV=FM−F0) was clearly reduced by visible radiation (VIS): UV-B caused a moderate extra-reduction in FV/FM. Exposure of leaves (V. vinifera L. cv. Bacchus) to UV or VIS lamps quenched the FM to similar extents; further, UV-B doses comparable to the field, quenched F0. A model was developed to describe how natural radiation intensities affect PS II and thereby change leaf fluorescence. Fitting theory to experiment was successful when the same FM yield for UV- and VIS-inactivated PS II was assumed, and for lower F0 yields of UVthan for VIS-inactivated PS II. It is deduced, that natural UV can produce inactivated PS II exhibiting relatively high FV/FM. The presence of UV-inactivated PS II is difficult to detect by measuring FV/FM in leaves. Hence, relative concentrations of intact PS II during outdoor exposure were derived from FM. These concentrations, but not FV/FM, correlated reasonably well with CO2 gas exchange measurements. Consequently, PS II inhibition by natural UV could be a main factor for UV inhibition of photosynthesis. Abbreviations: F0 and FM – minimum and maximum chlorophyll fluorescence from dark-adapted leaves; PS I and PS II – Photosystem I and II; TUV−A and TUV−B – epidermal transmittance for UV-A and UV-B radiation; VIS – visible radiation; UVA and UV-B – radiation in the range of 315 to 400 nm and 280 to 315 nm; V, VA and VAB – outside exposure to VIS, VIS+UV-B and VIS+UV-A+UV-B.

 

Lenk, S., L. Chaerle, E. E. Pfündel, G. Langsdorf, D. Hagenbeek, H.K. Lichtenthaler, D. Van Der Straeten and C.Buschmann (2007). “Multispectral fluorescence and reflectance imaging at the leaf level and its possible applications.” Journal of Experimental Botany 58(4): 807-814.

Images taken at different spectral bands are increasingly used for characterizing plants and their health status. In contrast to conventional point measurements, imaging detects the distribution and quantity of signals and thus improves the interpretation of fluorescence and reflectance signatures. In multispectral fluorescence and reflectance set-ups, images are separately acquired for the fluorescence in the blue, green, red, and far red, as well as for the reflectance in the green and in the near infrared regions. In addition, ‘reference’ colour images are taken with an RGB (red, green, blue) camera. Examples of imaging for the detection of photosynthetic activity, UV screening caused by UV-absorbing substances, fruit quality, leaf tissue structure, and disease symptoms are introduced. Subsequently, the different instrumentations used for multispectral fluorescence and reflectance imaging of leaves and fruits are discussed. Various types of irradiation and excitation light sources, detectors, and components for image acquisition and image processing are outlined. The acquired images (or image sequences) can be analysed either directly for each spectral range (wherein they were captured) or after calculating ratios of the different spectral bands. This analysis can be carried out for different regions of interest selected manually or (semi)-automatically. Fluorescence and reflectance imaging in different spectral bands represents a promising tool for non-destructive plant monitoring and a ‘road’ to a broad range of identification tasks.

 

Núñez-Olivera, E. J. M.-A., Rafael Tomás, Saúl Otero, and María Arróniz-Crespo (2006). “Physiological Effects of Solar Ultraviolet-B Exclusion on Two Cultivars of Vitis vinifera L. from La Rioja, Spain.” Am. J. Enol. Vitic 57: 441-448.

The response of two cultivars of Vitis vinifera (Tempranillo and Viura) typical of La Rioja to current levels of ultraviolet-B (UV-B) radiation was evaluated. Plants were exposed to near ambient radiation (PAR + UV-A + UV-B) or near ambient radiation 95% depleted in UV-B. At the end of the 16-day exposure, diurnal variations in photosynthetic pigment composition, soil-plantanalysis- development (SPAD) values, variables of chlorophyll fluorescence, methanol-extractable UV-absorbing compounds (MEUVAC), and sclerophylly were analyzed. The responses of the two cultivars to the reduction of solar UV-B were somewhat different. The only significant response of Viura was a decrease in MEUVAC. This response was also found in Tempranillo, together with a reduced action of the xanthophyll cycle and an increase in the concentrations of chlorophyll and carotenoids and in SPAD values. Thus, solar UV-B seems to cause slight damage in Tempranillo grapevines. This damage as compared to the almost unaltered Viura grapevines could be related to the lower capacity of Tempranillo to produce MEUVAC under solar UV-B. Given that the exclusion of solar UV-B causes only modest physiological effects, at least in the short term, both cultivars seem to be adapted to the high solar radiation typical of the Mediterranean climate, and their photosynthetic performance (derived from chlorophyll fluorescence variables) does not appear to be at risk from current levels of UV-B.

 

Pfündel, E. E. (2003). “Action of UV and visible radiation on chlorophyll fluorescence from darkadapted grape leaves (Vitis vinifera L.).” Photosynthesis Research 75(1): 29-39.

Grapevine plants (Vitis vinifera L. cv. Silvaner) were cultivated under shaded conditions in the absence of UV radiation in a greenhouse, and subsequently placed outdoors under filters transmitting natural radiation, or screening out the UV-B (280 to 315 nm), or screening out the UVA (315 to 400 nm) and the UV-B spectral range. All conditions decreased maximum chlorophyll fluorescence (FM) and increased minimum chlorophyll fluorescence (F0) from dark-adapted leaves; however, with increasing UV, FM quenching was stimulated but increases in F0 were reduced. The FV/FM ratio (where FV=FM-F0) was clearly reduced by visible radiation (VIS): UVB caused a moderate extra-reduction in FV/FM. Exposure of leaves (V. vinifera L. cv. Bacchus) to UV or VIS lamps quenched the FM to similar extents; further, UV-B doses comparable to the field, quenched F0. A model was developed to describe how natural radiation intensities affect PS II and thereby change leaf fluorescence. Fitting theory to experiment was successful when the same FM yield for UV- and VIS-inactivated PS II was assumed, and for lower F0 yields of UV- than for VIS-inactivated PS II. It is deduced, that natural UV can produce inactivated PS II exhibiting relatively high FV/FM. The presence of UV-inactivated PS II is difficult to detect by measuring FV/FM in leaves. Hence, relative concentrations of intact PS II during outdoor exposure were derived from FM. These concentrations, but not FV/FM, correlated reasonably well with CO2 gas exchange measurements. Consequently, PS II inhibition by natural UV could be a main factor for UV inhibition of photosynthesis.

 

Price, S. F., P.J. Breen, M. Valladao, and B.T. Watson (1995). “Cluster Sun Exposure and Quercetin in Pinot noir Grapes and Wine.” Am. J. Enol. Vitic 46(2): 187-194.

Anthocyanin and flavonol content of disks of sun-exposed Pinot noir (Vitis vinifera L.) berry skin were compared to disks from shaded berries from the same clusters. Anthocyanin content was not affected by sun exposure, but quercetin glycoside concentration of sun-exposed disks was 1.46 μg mm-2 for the sun-exposed disks compared to 0.14 μg mm-2 for the shaded. Wines were made from Pinot noir clusters from a single vineyard block from three different sun exposure levels: shaded, moderately exposed and highly exposed. The concentration of quercetin glycosides in wine was 4.5, 14.8, and 33.7 mg L-1 in the shaded, moderate and highly exposed treatments, respectively. The level of quercetin aglycone also increased with sun exposure. Cluster sun exposure appears to be the primary factor determining quercetin levels in grapes and wine. Wines from highly and moderately exposed cluster positions had higher total anthocyanin levels than those from shaded clusters, but wines from highly exposed clusters had 40% greater polymeric anthocyanins than the other two treatments. Caftaric acid, catechin, and epicatechin concentrations in wine were inversely related to cluster sun exposure. The low levels of caftaric acid in wines from sun-exposed clusters appeared to be related to hydrolysis of the tartaric ester, with wines from highly sun-exposed clusters having 50% more caffeic acid than moderate and 130% more than shaded clusters. Caffeic acid was not present in fruit samples. It is possible that the increase in polymeric anthocyanins in wines from sun-exposed clusters is directly related to quercetin levels. High wine quercetin levels may increase the rate of polymerization with potential stability and quality implications.

 

Spayd, S. E., J.M. Tarara, D.L. Mee, and J.C. Ferguson (2002). “Separation of Sunlight and Temperature Effects on the Composition of Vitis vinifera cv. Merlot Berries.” Am. J. Enol. Vitic 32(4): 171-181.

Anthocyanin and phenolic profiles of berry skins from Vitis vinifera cv. Merlot in the Yakima Valley of Washington were influenced by sun exposure and temperature in 1999 and 2000. Growing degree days (base 10°C) accumulated between veraison and harvest were lower in 2000 than in 1999. Total skin monomeric anthocyanin (TSMA) concentrations were higher in 2000 than in 1999 in any given treatment. Berry temperature was increased as much as 13°C above ambient and shaded cluster temperatures when clusters were exposed to sunlight, regardless of aspect for north-south oriented rows. However, maximum fruit temperatures were higher for clusters on the west side of the canopy because ambient temperatures were higher after 1200 hr. Temperatures of west-exposed clusters at times exceeded 40°C. East-exposed clusters had higher TSMA concentrations than west-exposed or shaded clusters. To separate light and temperature effects, west-exposed clusters were cooled to the temperature of shaded clusters and shaded clusters were heated to the temperature of west-exposed clusters. Exposure to sunlight increased TSMA concentrations regardless of temperature in both years. In 1999 and 2000, cooling sun-exposed clusters increased TSMA concentrations. Heating shaded clusters decreased TSMA concentrations in 1999, but had no effect during the cooler ripening period of 2000. Ultraviolet (UV) light barriers did not influence either cluster temperature or TSMA concentrations. Decreased TSMA concentrations in berry skins from west-exposed clusters were due to temperature and not to UV radiation. Exposure to solar radiation increased concentrations of the 3-glycosides of quercetin, kaempferol, and myricetin. In 2000, sun-exposed clusters, regardless of aspect, had almost 10 times greater concentrations of total flavonols than shaded clusters. UV-light barriers significantly reduced individual and total flavonol concentrations, while temperature had little to no effect on their concentrations.

 

Steel, C. C. a. M. K. (2000). “Environmental Effect on Lipids: Atmosphere and Temperature.” Biochemical Society Transactions 28: 883-885.

The carotenoid content was examined in leaf and berry tissues of grapevines (cv. Cabernet Sauvignon) grown either under ambient conditions or under polyester film to reduce UV light by 98%. Total carotenoids in leaves were less in vines grown under the UV screen. Levels of ­- carotene decreased with berry development around veraison. This effect was more pronounced in vines grown under reduced UV light. The lutein content of berries appeared to remain relatively constant with berry development, but levels were decreased under the UV screen. These observations are important for the wine industry because of the biosynthetic link between carotenoids and wine flavour and aroma compounds.

 

Zorer, R., T. Cobelli, D. Tomasi, L. Zulini, and M. Bertamini (2005). Effect of Temperature and Light Availability on Ripening of Vitis Vinifera L. CV. Pinot Noir. International Workshop on Advances in Grapevine and Wine Research, Venosa, Italy.

Air temperature is widely used to build ripening models but it is also well known that the sunlight exposure of grape clusters is important to berry composition and metabolism. Berry temperatures usually match the diurnal solar radiation curve but can be increased as much as 13 °C above ambient and shaded cluster temperatures when clusters are exposed to sunlight, regardless of aspect for north-south oriented rows. Differences in temperature between ambient air and exposed fruit increase as solar radiation increase and wind speed decrease. In the present work the ripening process in Vitis vinifera L. cv. Pinot noir was investigated by periodical sampling of 20 single clusters and °Brix, pH and total acidity determination. In parallel the light microclimate of clusters was characterized by means of hemispherical pictures taken at the cluster position in order to calculate the direct, diffuse and total radiation cumulated from veraison to the sampling date. Main microclimatic parameters (air and soil temperature, air humidity, solar global and diffuse radiation, insolation, precipitation) were acquired by an automatic meteorological station. The data have been used to apply different ripening models and the role of the single meteorological parameters in the ripening process has been investigated. The use of different combinations of base temperatures limits in degree-day calculations provided big improvement over the degree-day summation system based on the l0 °C threshold temperature value (Winkler ripening index; R2 = 0.901; p = 0.012). The most accurate fitting of the °Brix data was obtained at a optimum temperature of 18.7 °C (R2 = 0.998; p < 0.001). Among the main micrometeorological cumulated parameters the correlation with the ripening status (°Brix) was very high and significant for the mean daily soil (-10 cm) temperature (R2 = 0.889; p = 0.018), air temperature (R2 = 0.902; p = 0.014), daily insolation (R2 = 0.933; p = 0.007), diffuse (R2 = 0.911; p = 0.012), total (R2 = 0.942; p = 0.005) and direct radiation (R2 = 0.964; p = 0.002). The possibility to implement local ripening data to GIS-based models is finally discussed.