Sunlight nd Temperture Effects on Merlot Berries 171 Seprtion of Sunlight nd Temperture Effects on the Composition of Vitis vinifer cv. Merlot Berries S.E. Spyd, 1 * J.M. Trr, 2 D.L. Mee, 1 nd J.C. Ferguson 2 Anthocynin nd phenolic profiles of berry skins from Vitis vinifer cv. Merlot in the Ykim Vlley of Wshington were influenced by sun exposure nd temperture in 1999 nd 2000. Growing degree dys (bse 10 C) ccumulted between verison nd hrvest were lower in 2000 thn in 1999. Totl skin monomeric nthocynin (TSMA) concentrtions were higher in 2000 thn in 1999 in ny given tretment. Berry temperture ws incresed s much s 13 C bove mbient nd shded cluster tempertures when clusters were exposed to sunlight, regrdless of spect for north-south oriented rows. However, mximum fruit tempertures were higher for clusters on the west side of the cnopy becuse mbient tempertures were higher fter 1200 hr. Tempertures of west-exposed clusters t times exceeded 40 C. Est-exposed clusters hd higher TSMA concentrtions thn west-exposed or shded clusters. To seprte light nd temperture effects, west-exposed clusters were cooled to the temperture of shded clusters nd shded clusters were heted to the temperture of west-exposed clusters. Exposure to sunlight incresed TSMA concentrtions regrdless of temperture in both yers. In 1999 nd 2000, cooling sun-exposed clusters incresed TSMA concentrtions. Heting shded clusters decresed TSMA concentrtions in 1999, but hd no effect during the cooler ripening period of 2000. Ultrviolet (UV) light brriers did not influence either cluster temperture or TSMA concentrtions. Decresed TSMA concentrtions in berry skins from westexposed clusters were due to temperture nd not to UV rdition. Exposure to solr rdition incresed concentrtions of the 3-glycosides of quercetin, kempferol, nd myricetin. In 2000, sun-exposed clusters, regrdless of spect, hd lmost 10 times greter concentrtions of totl flvonols thn shded clusters. UV-light brriers significntly reduced individul nd totl flvonol concentrtions, while temperture hd little to no effect on their concentrtions. Key words: Cnopy mngement, light, microclimte, UV, color, het stress, photoregultion, soluble solids, cidity, ph 1 Extension Food Scientist/Food Scientist, nd former Reserch Technologist III, respectively; Deprtment of Food Science nd Humn Nutrition, Irrigted Agriculture Reserch nd Extension Center, Wshington Stte University, 24106 N. Bunn Rod, Prosser, WA 99350; 2 Reserch Horticulturist nd Electronics Technicin, respectively; Horticulturl Crops Reserch Unit, USDA- ARS, 24106 N. Bunn Rod, Prosser, WA 99350. *Corresponding uthor [Emil: spyds@wsu.edu; fx (509) 786-9370] Acknowledgments: The uthors thnk the Wshington Wine Advisory Committee for prtil support of this study. Mnuscript submitted December 2001; revised April 2002 Copyright 2002 by the Americn Society for Enology nd Viticulture. All rights reserved. Cnopy mngement hs received considerble reserch ttention during the pst severl decdes [5,18,26,27,28]. The intent of this reserch ws to develop viticulturl prctices tht provided dequte exposure of fruit to sunlight while providing dequte, but not excessive, lef re to ripen the fruit nd improve fruit composition t hrvest. These prctices included trellis systems nd lef, shoot, or prtil shoot removl (hedging). Cool climtes, where fruit mturtion my be limited, were to gret extent the impetus for much of this reserch. However, viticulturl prctices developed for climtes with limited solr rdition re t times dopted in other regions with little considertion for the effects of excessive exposure of fruit to solr rdition. To chieve mximum color development in wrm regions, prolonged exposure of clusters to sunlight should be voided [1]. With the dvent of viticulturl prctices tht resulted in much more open cnopies (for exmple, deficit irrigtion, lef removl, nd reduced use of nitrogen fertilizer) in estern Wshington, incresed sunburning of fruit ws observed, prticulrly on the west side of north-south oriented rows nd on the south side of est-west oriented rows. The reltionship between sunlight exposure nd temperture of grpe clusters is importnt to berry composition nd metbolism. Millr [22] showed tht berry tempertures prlleled the diurnl solr rdition curve. Differences in temperture between mbient ir nd exposed fruit incresed s solr rdition incresed nd wind speed decresed, s one might expect from het trnsfer principles. Smrt nd Sinclir [29], who pursued n energy blnce pproch, indicted tht solr rdition nd wind velocity were the two most importnt determinnts of fruit temperture: during the dy shortwve rdition ws the primry source of fruit wrming nd convection ws the primry source of het trnsfer wy from the cluster. Fruit size, lbedo, wind direction, nd net long-wve rdition were less importnt. They reported tht shded grpe berries typiclly were 2.4 C bove mbient, while hot-spot tempertures on tight nd loose clusters were up to 12.4 nd 11.1 C bove mbient, respectively. Elsewhere, sunlit leves nd clusters were 5 to 10 C higher thn shded leves nd fruit [16]. In nother study, shded clusters were cooler thn sun-exposed clusters during the dy, but were wrmer thn sun-exposed clusters t 171
172 Spyd et l. night [6], suggesting greter net rdition loss by the exposed berries t night. For red-fruited cultivrs, shding of clusters decresed color nd nthocynin concentrtions [9,30], decresed soluble solids [9,24], nd incresed titrtble cidity [9,24]. Exposure to sunlight incresed totl phenol concentrtion in Pinot noir skin disks, but did not ffect nthocynin concentrtions [23]. Concentrtions of quercetin glycosides were 10-fold greter in skin disks from sun-exposed berries thn from shded berries. The response of berry growth nd physiology to light vries during fruit development [7]. The effects of temperture on grpe berry composition hve been studied extensively, primrily in growth chmbers, glsshouses, nd phytotrons to compre constnt dy nd/or night tempertures [3,7,15,16,17,21]. In one phytotron study, cool dy temperture (15 C) during ripening improved color development in Crdinl, Pinot noir, nd Toky berries, while hot dy temperture (35 C) significntly reduced or completely inhibited formtion of nthocynins [17]. A cool night temperture (10 or 15 C) did not reverse the effect of hot dy temperture on berry color. Grpes from vines held t wrm dy (25 C) nd cool night (15 C) tempertures developed less color thn those from vines held t cool dy nd night tempertures (both 15 C). The higher nthocynin content t the cooler tempertures ws not relted to juice soluble solids concentrtions, which tended to be greter t the higher dy tempertures. In glsshouse, berry color development for Cbernet Suvignon ws greter when dy temperture ws constnt 20 C thn constnt 30 C, both with constnt night temperture of 15 C [3]. Soluble solids did not differ. At the higher dy temperture, berries hd higher proline nd mlte concentrtions. Seprting the effects of temperture nd sunlight on grpe berry composition is difficult becuse mny of the biochemicl pthwys re both light nd temperture sensitive. In phytotron study using continer-grown vines, colortion of Pinot noir grpes ws lwys less under low [5.38 x 10 3 to 2.15 x 10 4 Lx(500 to 2000 ft-c)] thn high [2.69 x 10 4 to 5.38 x 10 4 Lx (2500 to 5000 ft-c)] light conditions t either low (20 C) or high (30 C) temperture [15]. With constnt dytime temperture of 30 C, fruit tempertures were between 33 nd 35 C. Spectrophotometric mesurements indicted slight reduction in nthocynin concentrtion in Pinot noir berries grown t the higher temperture. Crdinl berry color ws more sensitive to high temperture (less color) but less sensitive to light intensity thn Pinot noir. Dytime fruit tempertures of 32 to 36 C nerly inhibited nthocynin synthesis in Crdinl. The objectives of this study were to exmine how the composition of Merlot grpes ws ffected by sunlight exposure nd to seprte, in situ, the effects of temperture from solr rdition on the nthocynin nd phenol composition of Merlot grpes. Mterils nd Methods The study ws conducted during 1999 nd 2000 t the Irrigted Agriculture Reserch nd Extension Center (IAREC) in Prosser, Wshington (lt. 46.30 N, long. 119.75 W) within 1.2-h vineyrd plnted in 1983. The experimentl plot ws plnted to Vitis vinifer L. cv. Merlot, comprising three rows of 13 vines ech, oriented N-S. Vines were double-trunked, trined to bilterl cordon t 1.2 m, nd spur-pruned. Ech row ws treted s replicte (three replictes). Ech cordon ws treted independently of its mte in terms of sunlight exposure on the clusters. Clusters of given cordon were either shded or sun-exposed by positioning shoots to the side of the cnopy tht ws to be shded. Shoots were brought over wind wire (1.5 m) nd tied to ctch wire (1.2 m) prllel to the cordon nd wind wires. Becuse one lyer of V. vinifer leves will bsorb 80 to 90% of incident solr rdition [27], this nturl shding technique ws expected to llow predominntly only diffuse light to strike the shded clusters. In 1999, berry smples were collected rndomly twice fter verison from clusters tht were (1) exposed to direct sunlight on the est side of the cnopy, (2) exposed to direct sunlight on the west side of the cnopy, (3) shded from sunlight on the est side of the cnopy, nd (4) shded from sunlight on the west side of the cnopy. Becuse no differences were found in the 1999 prehrvest smples from shded clusters, fruit from the two shded tretments ws pooled for nlysis t hrvest in 1999 nd both before nd t hrvest in 2000. Only one prehrvest smple ws obtined in 2000 becuse frost (-2.2 C) on 23 September curtiled the experiment. In 2000, n dditionl fruit exposure tretment ws dded to determine the influence of ultrviolet rdition (UV). Acrylic sheets (0.9 m x 1.2 m x 3.75 mm thick) tht either bsorbed (98% below 400 nm; Acrylite OP-2, Cyro Industries, Mt. Arlington, NJ) or trnsmitted UV (Acrylite OP-1, Cyro Industries) were instlled t 45 ngle, 0.5 to 0.8 m in front of west-fcing, sun-exposed fruit. The sheets extended from just bove the cnopy to just below the fruiting zone. Cluster tempertures were recorded for four clusters per cordon (n=8 per screening mteril). A temperture-stbilized UV-B sensor (280 to 320 nm; model CUV-B1, Kipp nd Zonen, Delft, The Netherlnds) ws used to determine the ctul trnsmittnce of the screening mterils. In situ temperture control study. All clusters used were on the west side of the cnopy of three djcent vines. Four clusters were monitored in 1999 nd 2000 in ech of six tretments: (1) sun-exposed (sun control); (2) shded by shoots (shde control); (3) sun-exposed nd chilled to the temperture of shded clusters (sun-cooled); (4) shded nd heted to the temperture of sun-exposed clusters (shde-heted); (5) sun-exposed with mbient ir blown on the cluster t sme rte s chilled ir (sun-blower); nd (6) shded with mbient ir blown on the cluster t sme rte s heted ir (shde-blower). The sun-blower nd shde-blower tretments served s controls for the effects of forced convection. The system used for heting nd cooling the clusters is described elsewhere [31]. Briefly, control clusters were used s thermostts to determine the temperture to which the treted clusters were to be heted or cooled. Shded clusters set the temperture for sun-exposed, cooled clusters, while sun-exposed clusters set the temperture for shded, heted clusters. The temperture of the treted clusters provided feedbck to the system to control delivery of
Sunlight nd Temperture Effects on Merlot Berries 173 heted or chilled ir. Tempertures were controlled from round bunch closure to hrvest. This period ws from 13 Aug to 12 Oct 1999 nd from 28 July to 24 Sept 2000. Becuse of the limited size of the experimentl plot nd the smll number of clusters involved, fruit ws smpled only when clusters were hrvested. In 1999, clusters were divided long the verticl xis into exterior nd interior fces. Berries from ll clusters within tretment were pooled nd then divided into three repetitions for lbortory nlysis. In 2000, ech cluster ws nlyzed seprtely. Interior nd exterior fce berries were not segregted. Micrometeorologicl mesurements. Severl berries on individul clusters were used to estimte verge cluster temperture nd the difference between exterior nd interior fces of the cluster. A four-junction, fine-wire (36 Americn Wire Guge [AWG]) thermocouple (type T [copper-constntn]) wired in prllel ws used s unit for ech mesurement. Individul junctions (2 mm long) were mnully inserted just beneth the berry skin t pproximtely the equtor of the sphere. Berries were selected from ner the cluster shoulder nd midwy long its verticl xis. Before verison, some berries developed necrosis round the thermocouple insertion hole. These junctions were moved to nerby berries on the sme fce of the cluster. After verison, no necrosis ws observed t the thermocouple entry points. Ambient ir tempertures inside the cnopy nd t 2 m bove the cnopy were mesured by shielded, spirted, fine-wire thermocouples (36 AWG; type T). Globl irrdince ws mesured by pyrnometer (model 8-48, Eppley Lbortories, Newport, RI). Irrdince t the fruiting zone ws mesured prllel to shded nd sun-exposed cordons by 1-m long tube solrimeters (model TSL, Delt-T Devices, Cmbridge, UK). All signls were scnned t 10-sec intervls nd verged every 12 min by dtlogger (CR-10X, Cmpbell Scientific, Logn, UT) tht lso controlled multiplexers designed specificlly for thermocouples (AM25T, Cmpbell Scientific, Logn, UT). Dt were collected continuously for 60 dys in 1999 nd 58 dys in 2000, pproximtely from bunch closure to hrvest. Wind speed t 2 m ws mesured by 3-cup nemometer (Wind Sentry, R.M. Young, Trverse City, MI) t the Public Agriculture Wether System sttion t the IAREC fcility. Signls were recorded every 10 sec nd verged every 15 min. Lbortory nlyses. Fifty to 100 berries from ech tretment were counted, weighed, nd used for fresh berry nlyses. Twenty berries were subsmpled from ech tretment nd frozen t -35 C for lter nthocynin nd phenol nlyses. Rohpect D5-L (Scott Lbortories, Sn Rfel, CA) ws dded to the equivlent of 1 ml of enzyme/kg of fresh berries. Berries were pureed in lbortory blender t high speed for 1 min. The homogente ws filtered through fluted filter pper (no. 588, Schleicher nd Schuell, Keene, NH). The filtrte ws used for determintion of percent soluble solids, ph, titrtble cidity (TA), nd totl color t 520 nm (TC520). Percent soluble solids ws mesured using temperture-compensting Abbé refrctometer (Model 10450, Americn Opticl Corp., Bufflo, NY). The ph ws mesured with ph meter (model 455, Corning Inc., Kennebunk, ME) stndrdized to ph 7.0 nd 4.0. Titrtble cidity ws determined by titrting 5 ml of juice diluted with 100 ml of boiling distilled wter to ph 8.2 with 0.1 N NOH nd ws expressed s g trtric cid/l. For TC520, 5 ml-liquot of juice ws diluted to volume of 25 ml with cidified ethnol (ph 1.0). Absorbnce ws mesured t 520 nm using spectrophotometer (DU 600, Beckmn, Irvine, CA). TC520 ws clculted by multiplying bsorbnce t 520 nm by the dilution fctor of five nd expressed s bsorbnce units per ml of juice. Ten frozen berries per smple were removed from the freezer the dy of extrction nd llowed to thw slightly to fcilitte removl of the skins. Whole skins were peeled from berries. Loose pulp ws removed from the bck of the skins by blotting with Kim-Wipe (Kimberly-Clrk Corportion, Roswell, GA). Using n 8-mm dimeter cork borer, two skin disks were removed from ech berry for totl of 20 disks per smple, representing bout 10 cm 2 of skin surfce. Disks were plced in 10-mL test tube to which were dded 2 ml of 100% ethnol contining 0.2% HCl nd homogenized (model PRO250, PRO Scientific Inc., Monroe, CT). The homogenizer ws rinsed with n dditionl 2 ml of cidified ethnol tht ws dded to the 10-mL tube contining the homogenized grpe skin. Smples were plced in the refrigertor overnight (c. 16 hr). The following morning smples were centrifuged t 1200 x g for 15 min. The superntnt ws trnsferred to 10-mL volumetric flsk. Smple pellets were extrcted two more times by mixing the pellet with 2 ml of cidified ethnol, holding for 2 hr under refrigertion, centrifuging, nd trnsferring the superntnt to the 10-mL volumetric flsk. Three milliliters of ultrpure wter (18 MΩ) were dded to ech volumetric flsk. The extrct ws tken to 10.0 ml with cidified ethnol. A more exhustive extrction performed (7 x 1 ml) on four of the smples indicted tht 97% of the nthocynins nd flvonols were extrcted using the triple extrction described bove (dt not presented). Smples were stored under nitrogen hedspce t -5 C. At the time of nlysis, extrcts were thwed t room temperture (c. 20 C) nd diluted 1:1 with ultrpure wter. All HPLC hrdwre ws from Dynmx (Rinin, Oklnd, CA) nd ws controlled by proprietry softwre (Dynmx 1.9). The system consisted of three pumps (model SD-200), n utosmpler (model AI-1A), photodiode rry detector (PDA; model PDA-1), nd fluorescence detector (model FL-2). Column temperture ws mintined t 35 C for ll seprtions. The method of Lmuel-Rventos nd Wterhouse [20] ws used for the 1999 grpe skin extrcts. The column ws Wters (Milford, MA) Novpk C18 (3.9 x 150 mm) with 4 µm prticle size nd gurd column of the sme pcking. In 2000 elunt A ws omitted becuse flvonoids nd nthocynins were the only phenols identified from the 1999 skin extrcts (Tble 1). Additionlly, the elunt rmp for B nd C ws djusted nd column length ws incresed to 250 mm to provide improved pek seprtion. Concentrtions of monomeric nthocynins nd totl monomeric nthocynins were expressed s µg mlvidin 3-glucoside/cm 2 skin. Experimentl design nd sttisticl nlyses. For the cluster loction study, the design ws rndomized complete block with rows s replictes for ll berry smples (3 replictes x 3
174 Spyd et l. Tble 1 Grdients for seprtion of nthocynins nd flvonols from grpe berry skin extrcts. 1999 2000 Proportion of Proportion of Time intervl elunt A in elunt B Time intervl elunt A in elunt B b (min) (%) (min) (%) 0 to 10 18 to 20 0 to 2 100 10 to 30 20 to 40 2 to 10 100 to 94 30 to 32 40 to 80 10 to 40 94 to 88 32 to 33 held t 80 40 to 60 88 to 75 33 to 36 80 to 18 60 to 64 75 to 10 64 to 69 held t 10 69 to 70 10 to 100 Eluent A ws 20% ultrpure wter nd 80% cetonitrile (v/v) contining 0.25 ml 85% phosphoric cid/l. Eluent B ws 85% phosphoric cid diluted to 1.0 L with ultrpure wter nd djusted to ph 1.5 s required. b Eluent A ws ultrpure wter contining 0.25 ml 85% phosphoric cid/l, djusted to ph 2.6 s required. Eluent B ws 20% ultrpure wter nd 80% cetonitrile (v/v) contining 0.25 ml 85% phosphoric cid/l. cluster loctions). Prehrvest berry smples tken on more thn one dte were treted s split-plot in time where pproprite. Dt were subjected to nlysis of vrince using the generl liner model, F-tests, orthogonl polynomil regression, stepwise multiple regression, nd Duncn s new multiple rnge test (p = 0.05) using SAS (Cry, NC). Results At the IAREC, growing degree dy (GDD) ccumultions from 1 April to 31 Oct (bse temperture 10 C) were 1247 in 1999 nd 1384 in 2000. The verge GDD for the period 1955 to 2000 is 1389. The pttern of GDD ccumultion differed between yers. In 1999, GDD ccumultion ws slow from April through July, the third lowest during the period 1955 to 1999. During the sme period in 2000, GDD ccumultion ws the twelfth highest between 1955 nd 2000. Conversely, between 1 Aug nd hrvest, the trend ws reversed between the two yers, with 2000 cooler thn 1999 (Figure 1). Tempertures for Figure 1 Growing degree dy ccumultion (bse 10 C) t WSU, Prosser from DOY 213 to 278, 1999 nd 2000. this period were wrmer thn verge in 1999 nd lower thn verge in 2000. In situ temperture control study. Fruit temperture ccumultion ws greter from bunch closure to hrvest in 2000 thn in 1999 (Tble 2). Between initition of verison for est-exposed clusters, which we will refer to s verison in the reminder of the text, nd hrvest there were 54 dys in 1999 nd 33 dys in 2000. Absolute temperture ccumultion by the fruit ws greter in 1999 thn 2000 becuse of the longer period. However, on verge, more growing degrees dys were ccumulted per dy in 2000. Generlly, temperture ccumultions by heted nd cooled clusters reflected the temperture regimens we were trying to chieve. Temperture ccumultions of cooled, sunlit clusters were within 3 GDD of shded clusters in both growing sesons. Shde-heted clusters were within 14 GDD of sunlit control clusters for both yers nd mesurement periods. In both yers, temperture ccumultions for the shde-blower nd sun-blower fruit were intermedite to their control nd temperture-mnipulted counterprts. During the 1999 ripening period, minimum berry tempertures rnged from -1.2 to +0.4 C nd occurred before dwn on either 29 Sept or 3 Oct. In 2000, frost occurred on the night of 23 to 24 Sept. Air temperture ws below 0 C for 3.8 hr with the minimum ir temperture reching -2.4 C. Minimum berry tempertures rnged from -2.1 to -3.6 C nd were below 0 C for 3.4 to 4.0 hr. Ambient globl irrdince ccumulted from verison to hrvest ws 1,007 MJ/m 2 in 1999 nd 643 MJ/m 2 in 2000. The difference in ccumulted irrdince ws due to the difference in the length of time between verison nd hrvest between the two yers. Solr rdition exposure t the fruiting zone of exposed clusters ws bout 60% of mbient, wheres bout 10% of mbient levels of solr rdition were incident on shded clusters (Tble 2). Between 19 Aug nd 21 Sept, corresponding to the verison to hrvest period in 2000, cumultive solr rdition exposure ws similr in both yers (dt not shown). Neither temperture nor exposure to sunlight ffected berry mss within either yer, but berry mss ws greter in 2000 (Tble 3). Although there were some differences in soluble solids mong the six temperture-sunlight tretments, there were no consistent ptterns. Whether bsed on juice concentrtion or per berry (dt not shown), TA of sun-control berries ws higher in 1999 thn in 2000, while it ws similr in concentrtion between the two yers for shde-control berries. In both yers, sun-cooled fruit hd the highest men concentrtion of soluble solids, but this tretment did not differ from the other two sunlit tretments. Also in both yers, shde-heted nd suncontrol berries hd the lowest nd shde-control berries hd the highest TA. Titrtble cidity did not differ mong ny of the sunlit tretments in either yer. Titrtble cidity of shdeblower fruit ws lower thn shde-control fruit nd higher thn shde-heted fruit; it ws similr to tht of sun-blower nd suncooled fruit. Fruit ph ws inversely relted to TA. In 1999, sun-cooled clusters hd the highest nd shdeheted clusters hd the lowest TC520 of the six in situ temper-
Sunlight nd Temperture Effects on Merlot Berries 175 Tble 2 Temperture ccumultion by clusters, expressed s growing degree dys, s clculted from ctul fruit tempertures using bse temperture of 10 C. Cumultive exposure to solr rdition determined from tube solrimeters plced in the fruiting zone. 1999 2000 Growing degree dys Growing degree dys ( C) ( C) Bunch Solr Bunch Solr closure to Verison rdition closure to Verison rdition Tretments hrvest to hrvest b (MJ/m 2 ) hrvest to hrvest b (MJ/m 2 ) Sun Control 495 434 549 586 289 360 Blower 467 406 565 272 Cooled 442 385 519 252 Shde Control 439 382 129 521 250 69 Blower 443 385 551 266 Heted 505 443 602 297 1999 = 13 Aug to 12 Oct; 2000 = 9 Aug to 25 Sept. b 1999 = 20 Aug to 12 Oct; 2000 = 23 Aug to 25 Sept. ture control tretments (Tble 3). TC520 ws lower nd differences in TC520 mong tretments were not s gret in 2000 s in 1999. Lower TC520 in 2000 my hve resulted from higher berry mss. Trends indicted tht shde-control, shde-heted, nd sun-control clusters hd the lest TC520, while sunlit-cooled clusters hd the most TC520. In 1999, cluster fce hd no effect on berry composition, whether or not the cluster ws shded or sunlit. Becuse TC520 did not differ in 1999, the following procedures were followed: (1) in 1999, berries from the exterior nd interior cluster fces were pooled for individul nthocynin determintions nd (2) individul nthocynins were not determined for sun- nd shde-blower tretments; nd (3) in 2000 no differentition in cluster fce ws mde. Although TC520 of juice from whole berry mcerte ws greter in 1999, totl nthocynin concentrtions in skin extrcts were bout 50% higher in 2000 (Tble 4), suggesting the dilution of TC520 in the whole berry extrcts due to lrger berry mss (Tble 3). Totl monomeric skin nthocynins (TSMA) were ffected by sunlight nd temperture in both yers, but not to the sme degree (Tble 4). Of the four tretments in 1999 nd six tretments in 2000, sun-cooled clusters tended to hve the highest TSMA concentrtions. In 1999 shde-heted clusters hd the lowest TSMA concentrtions of the four tretments. In 2000, the three shde-cluster tretments tended to hve the lowest TSMA concentrtions. However, shde-blower clusters did not differ from sun-control clusters. We exmined the effects of temperture on TSMA concentrtion by compring the difference in concentrtion between tretments within ech of the light conditions. In 1999, for sunexposed clusters, nthocynin concentrtion ws 87 µg/cm 2 skin higher in cooled clusters thn in the control clusters (Tble 4). For shded clusters, TSMA concentrtion ws 92 µg/cm 2 skin higher in nonheted, control clusters thn in heted clusters. Therefore, under both light conditions, differences in TSMA concentrtions between the control nd the temperture-modified clusters were bout 90 µg/cm 2 skin. This vlue represents the influence of temperture on TSMA concentrtion. Similrly, we compred the effects of light on TSMA concentrtion by compring the difference in concentrtion between tretments within ech of the temperture regimes. For the high temperture clusters, TSMA concentrtion ws 120 µg/cm 2 higher in light-exposed clusters thn in shdedheted clusters. For the cool temperture clusters, TSMA concentrtion ws 115 µg/cm 2 higher in sun-cooled clusters thn in shde-control clusters. Therefore, under both temperture conditions, differences in TSMA concentrtion between sunlit nd shded clusters of the sme temperture verged 117 µg/cm 2 of skin, representing the influence of light on TSMA concentrtion. In 2000 sun-exposed clusters, TSMA concentrtion ws 102 µg/cm 2 skin higher for cooled clusters thn the control clusters. For shded clusters, heting clusters hd no effect on TSMA concentrtions. Agin, we compred the effects of light on TSMA concentrtion by compring the difference in concentrtion between tretments within ech of the temperture regimes. For the high temperture clusters, Tble 3 Effect of sun exposure nd temperture on Merlot berry composition t hrvest, 1999 to 2000. Berry Soluble Totl mss solids TA color (g/berry) (%) (%) ph (AU/mL) b 1999 Tretment c Sun Control 1.00 d 23.2c 0.60c 3.59bc 16.2b Blower 1.08 24.1b 0.64bc 3.61b 17.3b Cooled 1.02 24.4 0.62bc 3.63b 21.7 Shde Control 1.13 23.8b 0.73 3.56c 16.9b Blower 1.00 23.8b 0.66b 3.60bc 17.0b Heted 1.06 23.2c 0.59c 3.68 12.5c Cluster fce e Exterior 1.03 23.7 0.63 3.62 16.8 Interior 1.06 23.8 0.65 3.60 16.9 2000 Tretment f Sun Control 1.32 22.3b 0.51cd 3.78bc 11.6b Blower 1.23 22.2b 0.59bc 3.70c 14.3b Cooled 1.15 23.0 0.59bc 3.70c 15.2 Shde Control 1.33 21.2c 0.76 3.73bc 10.7b Blower 1.28 22.3b 0.65b 3.78b 13.1b Heted 1.27 21.6bc 0.46d 3.89 10.9b Expressed s trtric cid. b Absorbnce t 520 nm of n cidified ethnol extrct, ph 1.0. c Mens pooled cross three repetitions nd two cluster fces. d Men seprtion within columns within tretment, cluster fce, nd yers by Duncn s new multiple rnge test (p = 0.05). Mens followed by the sme letter do not differ. e Mens pooled cross three repetitions nd six heting/cooling tretments. f Mens pooled cross four repetitions.
176 Spyd et l. Tble 4 Influence of cluster temperture nd exposure to sunlight on nthocynin nd flvonol concentrtions in Merlot berry skins, 1999 to 2000. 1999 2000 Sun Shde Sun Shde Control Cooled Control Heted Control Blower Cooled Control Blower Heted Totl nthocynins 349.0b b 436.2 321.3b 228.9c 529.9b 597.7 631.9 414.7c 501.0b 415.2c Delphinidin 3-glucoside 60.1b 83.9 59.9b 29.8c 110.7c 132.0b 159.3 75.6d 96.2c 54.6e Cynidin 3-glucoside 17.9b 31.7 16.8b 7.50c 39.0b 47.4b 60.7 20.9c 22.6c 10.1c Petunidin 3-glucoside 39.3b 51.8 37.3b 20.6c 63.2bc 71.8b 80.8 45.4d 56.3c 38.5d Peonidin 3-glucoside 31.1b 49.3 29.8b 17.2c 45.0bc 53.2b 60.4 32.6de 35.6cd 22.0e Mlvidin 3-glucoside 96.7b 107.2 84.0b 68.1b 135.8 148.2 138.4 118.3 142.0 138.0 Delphinidin 3-glucoside cette 11.5 13.3 12.0 6.3b 18.4bc 22.0b 24.2 17.2c 20.3bc 12.5d Cynidin 3-glucoside cette 4.40 5.53 4.20 2.10b 6.65b 7.30b 8.45 4.45cd 5.52bc 2.90d Petunidin 3-glucoside cette 10.5 11.9 10.3.10b 14.7 15.8 16.3 13.5b 16.0 11.8b Peonidin 3-glucoside cette 7.57b 8.63 7.37b 5.60b 8.48 9.08 8.65 7.82 8.92 8.30 Mlvidin 3-glucoside cette 32.1 33.4 28.5 29.8 44.5bc 45.0bc 37.3c 43.6bc 51.8b 60.7 Delphinidin/cynidin 3-glucoside coumrte 6.10b 7.27 5.53b 5.13b 6.60 7.28 7.20 4.00b 4.88b 4.25b Petunidin 3-glucoside coumrte 7.00 7.00 5.33b 4.67b 7.98 8.80 7.38 5.58b 7.40 7.38 Peonidin/mlvidin 3-glucoside coumrte 25.0 25.7 20.3 25.0 28.7b 30.1b 22.8b 25.8b 33.6b 44.1 Totl flvonols c d 82.7 82.7 76.0 10.2b 22.9b 17.8b Quercetin 3-glucoside c 22.0b 31.7 7.13c 7.27c 59.9 62.8 56.6 7.50b 14.6b 12.5b Myricetin 3-glucoside c 9.12 8.50 8.15 0.01b 3.15b 1.80b Kempferol 3-glucoside c 13.7 11.4 11.3 2.68c 6.72b 4.80bc Expressed s µg mlvidin 3-glucoside chloride/cm 2 skin; bbrevited TSMA in text. b Men seprtion within yers within rows by Duncn s new multiple rnge test (p = 0.05). Mens followed by the sme letter do not differ. c Expressed s µg quercetin 3-glucoside/cm 2 skin. d Not determined in 1999. TSMA concentrtion ws 115 µg/cm 2 skin higher in exposed clusters thn in shde-heted clusters. For the cool temperture clusters, TSMA concentrtion ws 217 µg/cm 2 skin higher in sun-cooled clusters thn in shde-control clusters. In 1999, the response of individul nthocynins to light nd temperture tretments tended to follow the pttern of TSMA concentrtion with lower individul pigment concentrtions in berry skins tht were exposed to higher tempertures or were shded (Tble 4). These trends were not s cler in 2000 s in 1999, lthough sun-cooled clusters tended to hve the highest concentrtion of pigments. Using stepwise multiple regression, 92% of the vribility in totl nthocynin concentrtion in the skins ws ccounted for by petunidin 3-glucoside. Skins from sun-exposed clusters hd 3 to 4.5 times higher concentrtions of quercetin 3-glucoside thn skins from shded clusters (Tble 4). Although sunlight ws the overriding fctor influencing quercetin 3-glucoside concentrtions, cooling the sun-exposed clusters incresed quercetin 3-glucoside concentrtions by bout 40% in 1999. In 2000, quercetin 3-glucoside concentrtions were four to eight times greter in skins from sun-exposed clusters thn in those from shded clusters. Kempferol 3-glucoside ws 1.5- to 5-fold greter in skins from sun-exposed thn shded clusters. Cluster temperture did not ffect concentrtion of the three flvonols in 2000. UV brriers. Berry tempertures behind the UV blocking nd UV pssing screens were not mesurbly different from those of unscreened, west-exposed fruit (Figure 2). Thus, ny effect of the screening mterils on fruit composition ws not due to differences in fruit temperture. The crylic mteril deemed UV-bsorbing trnsmitted n verge of 4.2% of UV- B over the course of dy, wheres the UV-trnsmitting mteril only trnsmitted 56% of incident UV-B (dt not shown). Incident UV-B t the fruiting zone verged 88% of the mbient (sky) vlue. Blocking the UV wvebnd from sun-exposed clusters on the west side of the cnopy did not ffect berry mss or soluble solids (Tble 5). The effects of the two brriers on TA nd ph were not consistent, while TC520 of the cidified ethnol ex- Figure 2 Berry tempertures from clusters tht were exposed to the sun on west side of the cnopy, west-exposed but behind UV bsorbing mteril, or west-exposed but behind UV-trnsmitting mteril. Dt collected 10 dys to one week before hrvest, 2000.
Sunlight nd Temperture Effects on Merlot Berries 177 Tble 5 Effect of UV rdition on nthocynin nd flvonol concentrtions in Merlot berry skins, 2000. Tretment UV brriers Control Trnsmitting Absorbing Berry composition Berry mss (g) 1.23 1.25 1.24 Soluble solids (%) 22.9 22.2 22.0 Titrtble cidity (%) b 0.55 0.48b 0.53b ph 3.64b 3.78 3.75b Totl color c 11.8 9.6b 8.4b Skin nthocynins nd flvonols Totl nthocynins d 592.6 551.0 561.8 Delphinidin 3-glucoside d 132.4 108.3 108.3 Cynidin 3-glucoside d 54.0 33.6b 31.9b Petunidin 3-glucoside d 69.9 63.6 63.6 Peonidin 3-glucoside d 54.6 43.1b 30.6b Mlvidin 3-glucoside d 135.1 148.7 151.8 Delphinidin 3-glucoside cette d 22.2 19.8 21.3 Cynidin 3-glucoside cette d 8.98 5.6b 5.6b Petunidin 3-glucoside cette d 16.0 14.6 15.3 Peonidin 3-glucoside cette d 10.0 9.0 9.0 Mlvidin 3-glucoside cette d 43.7 50.6 49.3 Delphinidin/cynidin 3-glucoside coumrte d 7.2 5.8b 4.7b Petunidin 3-glucoside coumrte d 8.2 8.9 8.0 Peonidin/mlvidin 3-glucoside coumrte d 30.6b 39.2 36.6b Totl flvonols e 71.3 67.0 40.8b Quercetin 3-glucoside e 52.9 50.2 31.2b Myricetin 3-glucoside e 7.4 6.3 1.9b Kempferol 3-glucoside e 11.0 10.5 7.7b Men seprtion within rows by Duncn s new multiple rnge test (p = 0.05). Mens followed by the sme letter do not differ. Mens were pooled cross four repetitions. b Expressed s trtric cid. c Absorbnce t 520 nm of n cidified ethnol extrct, ph 1.0. d Expressed s µg mlvidin 3-glucoside chloride/cm 2 skin; bbrevited TSMA in text. e Expressed s µg quercetin 3-glucoside/cm 2 skin. trct ws reduced s compred to the control. However, TSMA concentrtions did not differ between the two UV pnels nd the control clusters. Some of the individul nthocynins were ffected by UV screening. Concentrtions of the 3-glucosides of quercetin, myricetin, nd kempferol were gretly reduced when UV rdition ws blocked from the clusters. Cluster loction: Fruit temperture. Of the three cluster loctions (est-exposed, west-exposed, nd shded), bsolute fruit tempertures were highest on the est side before solr noon nd on the west side fter solr noon (Figure 3). Est-exposed fruit wrmed erlier in the dy thn west-exposed fruit nd remined ner mbient shde tempertures during the fternoon. Grpe berries exposed to sunlight were wrmer thn berries shded from sunlight by the grpevine cnopy (Figure 4). The mximum dily differences in temperture ( T mx ) between est-exposed nd shded berries rnged from 3.3 to 11.7 C (between 6.0 nd 10.7 C in 2000) on dys with cler skies, nd generlly occurred between 0800 nd 1000 hr LST. This sizble rnge on dys with similr irrdince ws due to vritions in wind speed, with more effective convection wy from the exposed clusters thn from those in the reltively clm interior of the cnopy (dt not shown). Dily T mx between west-exposed nd shded berries ws 2.5 to 9.2 C (between 3.8 nd 9.7 C in 2000) on dys with cler skies. Agin, the vribility in T mx under similr irrdince ws due to differences in convection (wind speed). Generlly, T mx occurred between 1400 nd 1600 hr LST. In both yers, on dys with cler skies the exposed berries on either side of the cnopy were 4 to 13 C wrmer thn mbient ir t reference height t the time of dily T mx (dt not Figure 3 Typicl diurnl pttern of berry tempertures for fruit exposed to sunlight on the est or west sides of the cnopy, or shded from sunlight by the cnopy, on dy with cler skies. Shded tempertures re the men of clusters from both est nd west sides of the vine. Solr rdition ws mesured on-site with pyrnometer. (A) DOY 234 in 1999; (B) DOY 234 in 2000. In both yers, fruit ws pproching verison.
178 Spyd et l. Tble 6 Influence of cluster position on ccumultion of growing degree hours nd dys bsed on Merlot berry tempertures between initition of monitoring (c. bunch closure) nd hrvest nd between verison nd hrvest in 1999 nd 2000 (10 C used s bse temperture). Strt of monitoring to hrvest Verison to hrvest Cluster Degree hours Degree dys Degree hours Degree dys position ( h) ( d) ( h) ( d) 1999 13 Aug to 12 Oct 20 Aug to 12 Oct Est exposed 12,422 504 10,617 442 Est shded 10,422 434 9,089 379 West exposed 11,821 493 10,407 434 West shded 10,554 440 9,227 384 2000 9 Aug to 25 Sept 23 Aug to 25 Sept Est exposed 10,015 417 7,399 308 Est shded 8,852 369 6,507 271 West exposed 9,979 416 7,441 310 West shded 8,935 372 6,603 275 UV pss 9,913 413 7,360 307 UV block 9,739 406 7,219 301 Tble 7 Number of hours Merlot berry temperture exceeded selected temperture thresholds from bout bunch closure to hrvest, 1999 to 2000. Figure 4 Difference in fruit temperture ( T) between fruit exposed to sunlight (est-exposed or west-exposed) nd fruit shded by the cnopy on the sme side of the vine. Arrows indicte solr noon. (A) Postverison, 1999. DOY 261 to 264 hd cler skies nd mximum mid-dy irrdince of 720 to 725 W/m 2. (B) Postverison, 2000. DOY 265 ws cloudy with verge mid-dy irrdince of 250 W/m 2. DOY 266 nd 267 mid-dy irrdince ws 705 W/m 2 but verge wind speed differed between the dys. shown). Only the time of T mx differed; its mgnitude ws similr for the two sides of the cnopy. An indictor of fruit exposure to het ws constructed by clculting GDD from berry tempertures t ech cluster loction (Tble 6). In both yers, between bunch closure nd hrvest or between verison nd hrvest, there ws little difference (~2%) in the ccumultion of GDD between est- nd westexposed clusters. Shded clusters consistently ccumulted fewer GDD thn sun-exposed clusters. Clusters screened by the UV mterils ccumulted similr numbers of GDD s unscreened, west-exposed clusters. Accumulted temperture, lthough n importnt indictor, my not be s criticl to fruit physiology s the length of time the berries re subjected to specific tempertures. Threshold tempertures of 30, 35, nd 40 C were selected to determine differences in high temperture durtion mong the four cluster exposures (Tble 7). The number of hours bove 30 C ws less in 2000 thn in 1999 for ll cluster loctions. During both growing sesons, est-shded clusters experienced the lowest number of hours t tempertures greter thn 30 C, while westexposed clusters hd the highest number of hours. Perhps the Threshold temperture ( C) Cluster position >30 >35 >40 1999 (1437 totl hours of monitoring from 13 Aug to 12 Oct) Est exposed 148.2 3.2 0.0 Est shded 53.2 0.0 0.0 West exposed 181.4 73.6 2.8 West shded 83.0 0.0 0.0 2000 (1094 totl hours of monitoring from 9 Aug to 25 Sept) Est exposed 114.6 7.6 0.0 Est shded 45.0 2.6 0.0 West exposed 149.6 67.4 2.6 West shded 61.0 2.6 0.0 gretest differences in fruit tempertures mong the four cluster loctions were in the number of hours bove 35 C. In both yers, west-exposed clusters were bove 35 C for more thn 65 hr between bunch closure nd hrvest, while clusters in the other three loctions were bove 35 C for no more thn 7.6 hr. Of the four loctions, only west-exposed clusters reched tempertures greter thn 40 C in either yer. Cluster loction: Prehrvest berry composition. In 1999 nd 2000, smple dte nd cluster loction influenced the composition of berries in the prehrvest smples. There were no interctions between smple dte nd cluster loction (dt not shown). Therefore, only the min effects will be presented (Tbles 8 nd 9). Berry mss decresed between smpling dtes in both 1999 nd 2000 (Tble 8). In 1999, soluble solids, ph, nd TC520 incresed, while TA did not differ between smpling dtes. In 2000, soluble solids, TA, nd TC520 were lower on 25 Sept thn on 21 Sept. The decrese in soluble solids nd
Sunlight nd Temperture Effects on Merlot Berries 179 TC520 probbly resulted from severl hours below 0 C on 23 Sept tht dmged the fruit, forcing hrvest on 25 Sept. In 1999, berries on the west side of the cnopy weighed less thn ber- Tble 8 Min effects of smple dte nd cluster position on berry mss nd composition of Merlot, 1999 nd 2000. Soluble Totl Berry mss solids TA color (g/berry) (%) (%) ph (AU/mL) b 1999 Dte 28 Sept 1.23 c 22.2b 0.74 3.43b 13.9b 7 Oct 1.19 23.6 0.72 3.61 16.8 Cluster position Est exposed 1.27 23.0b 0.71b 3.50b 18.4 Est shded 1.29 23.3 0.81b 3.49b 16.7b West exposed 1.15b 22.5b 0.59c 3.62 11.6c West shded 1.14b 22.9b 0.82 3.46b 14.7b 2000 Dte 21 Sept 1.45 23.4 0.67 3.59b 15.6 26 Sept 1.29b 22.4b 0.60b 3.65 14.3b Cluster position Est exposed 1.47 23.2 0.61b 3.61b 18.0 Shded 1.35 22.4b 0.76 3.55c 13.2b West exposed 1.30 22.7b 0.52c 3.71 13.7b Expressed s trtric cid. b Absorbnce t 520 nm of n cidified ethnol extrct, ph 1.0. c Men seprtion within columns within yer within min effect by Duncn s new multiple rnge test (p = 0.05). Mens followed by the sme letter do not differ. ries on the est side of the cnopy. Shded berries on the west side of the cnopy tended to hve lower soluble solids thn their est-side counterprts, but the mximum difference in soluble solids mong ll cluster loctions ws only 0.8%. Titrtble cidity ws highest in shded fruit, followed by est-exposed nd the lowest concentrtion in west-exposed fruit. West-exposed fruit hd the highest ph of the four cluster loctions. TC520 ws highest for est-exposed nd lowest for west-exposed clusters. In 2000, shded clusters were smpled from both sides of the cnopy for combined shded fruit smple. Cluster loction did not ffect berry mss. As in 1999, the mximum difference in soluble solids ws 0.8% mong ll cluster loctions, with est-exposed fruit hving the highest nd shded fruit hving the lowest concentrtions. Titrtble cidity reflected berry tempertures. Shded berries hd the highest TA followed by est-exposed berries. Berry ph ws inversely relted to TA. TC520 ws highest in est-exposed fruit with no difference in TC520 between shded nd west-exposed fruit. On 5 Sept 2000 on the sme vine, bsed on berry color, westexposed clusters pprently were still in the erly stges of verison, while most est-exposed clusters were fully colored. This extreme difference ws not noticed in 1999. Preverison tempertures in 2000 were wrmer thn during the sme period in 1999. Merlot berry skins were nlyzed for chnges in the distribution of individul nthocynins on ech of the two prehrvest smple dtes nd on the dy of hrvest in 1999 nd on one prehrvest smple dte in 2000 (Tble 9). In 1999 cluster loction contributed more to the vribility in concentrtion of individul monomeric nthocynins nd TSMA concentrtions Tble 9 Influence of smple dte nd cluster position on concentrtion of nthocynins nd flvonols in skins of Merlot berries, 1999 to 2000. 1999 21 Sept 2000 Smple dte Cluster loction Cluster loction 28 Sept 7 Oct 13 Oct Est Shde West Est Shde West Totl nthocynins 353.6 b 365.4 409.4 433.0 378.3b 317.2c 784.8 521.8b 545.3b Delphinidin 3-glucoside 66.0 64.4 70.2 81.8 68.6b 50.2c 183.5 115.9b 112.9b Cynidin 3-glucoside 23.4b 25.1 21.8c 29.4 24.4b 16.4c 50.3 38.5 45.7 Petunidin 3-glucoside 41.6 42.8 45.9 51.7 44.4b 34.3c 105.8 63.1b 63.1b Peonidin 3-glucoside 36.7 39.4 40.2 45.3 39.8b 31.3c 64.9 47.2 47.2 Mlvidin 3-glucoside 87.0b 93.2b 108.8 110.7 91.4b 86.9b 206.0 126.3b 134.5b Delphinidin 3-glucoside cette 11.7 12.6 13.5 13.5 14.8 9.54b 25.7 21.3 18.1 Cynidin 3-glucoside cette 4.74 4.91 5.08 5.16 5.58 4.00b 6.73 6.80 7.07 Petunidin 3-glucoside cette 10.4 23.0 12.6 11.7 24.9 9.30 19.1 14.6 13.5 Peonidin 3-glucoside cette 7.44 8.32 9.34 8.34b 9.09 7.67b 9.40 9.00 8.70 Mlvidin 3-glucoside cette 29.6b 29.8b 37.7 33.9 32.1 31.0 55.5 42.7b 40.3b Delphinidin/cynidin 3-glucoside coumrte 5.77b 6.61b 7.16 6.48 6.39 6.67 7.90 5.60 6.77 Petunidin 3-glucoside coumrte 6.50 5.44 7.44 7.67 6.17b 5.56b 11.9 6.57b 8.6b Peonidin/mlvidin 3-glucoside coumrte 22.5b 22.2b 29.6 27.2 22.9b 24.1b 38.0 26.6b 31.7b Totl flvonols c 111.1 12.7b 111.1 Quercetin 3-glucoside c 29.6 25.6b 18.4c 34.4 9.47b 32.4 76.6 8.48b 82.8 Myricetin derivtive c 22.9 4.23c 15.4b Kempferol 3-glucoside c 11.6 0.01b 12.9 Expressed s µg mlvidin 3-glucoside equivlents/cm 2 skin; bbrevited TMSA in text. b Men seprtion within rows within yers within smple dte nd cluster position by Duncn s new multiple rnge test (p = 0.05). Mens followed by the sme letter do not differ. c Expressed s µg quercetin 3-glucoside/cm 2 skin.
180 Spyd et l. in skin tissue thn did dte of smpling. There were no significnt interctions between dte of smpling nd cluster loction. Therefore, only min effect mens of dte nd cluster loction re shown. With mens pooled cross cluster loction, mlvidin 3-glucoside ws the only nonsubstituted nthocynin to increse in concentrtion during the smpling period. In 1999, TSMA concentrtion tended to increse with time. In 1999, TSMA concentrtion differed mong cluster loctions with concentrtion decresing from est-exposed to shded to west-exposed clusters (Tble 9). Est-exposed clusters hd the highest concentrtions of ech of the nonsubstituted nthocynins, while west-exposed clusters hd the lowest concentrtions. Shded clusters were intermedite to est- nd west-exposed clusters, with the exception of mlvidin 3-glucoside where shded nd west-exposed clusters hd similr skin concentrtions. In 2000, concentrtions of TSMA nd severl of the individul nthocynins were highest in the berry skins of est-exposed clusters, while shded nd west-exposed clusters did not differ. In both 1999 nd 2000, quercetin 3-glucoside concentrtion ws lowest in the skins of shded berries (Tble 9). In 2000, we tenttively identified derivtive of myricetin, bsed on retention time, nd confirmed the presence of kempferol 3- glucoside. Both of these flvonols responded to sunlight exposure in the mnner of quercetin 3-glucoside. Totl flvonol concentrtion ws lmost 10 times greter in skins of sun-exposed thn shded clusters, regrdless of spect. Combined light nd temperture effects. Forwrd selection, stepwise multiple regression ws used to develop model for fctors contributing to nthocynin ccumultion in berry skins. Men TSMA concentrtions from the in situ nd the cluster loction studies were regressed ginst their corresponding verison-to-hrvest GDD ccumultion, ccumulted solr rdition, nd hours fruit temperture exceeded 30, 35, nd 40 C. For the cluster loction study, the dy of hrvest smple in 1999 nd the prehrvest smple in 2000 were used in the regression. To be retined in the model, the contribution of vrible hd to be significnt t p 0.15. Across the two yers nd two studies, GDD between verison nd hrvest ws the first independent vrible dded to the model nd ccounted for bout 45% of the vribility in TSMA concentrtions. Accumulted solr rdition (prtil r 2 =0.306) ws the second vrible dded, giving model tht ccounted for 76% of the vribility in TSMA concentrtions (r 2 =0.758). Number of hours bove 35 nd 30 C were included in the finl model, in tht order. However, these vribles ccounted for fr less vribility thn GDD nd ccumulted solr rdition (prtil r 2 -vlues of 0.046 nd 0.076, respectively). The finl model generted ws: TSMA=869 + (-1.88*GDD) + (1.67*SR) + (-3.24*H35) + (1.67*H30) where TSMA is totl skin monomeric nthocynin concentrtion (µg/cm 2 ); GDD is growing degree dys (bse 10 C) from verison to hrvest; SR is ccumulted solr rdition (MJ/m 2 ) from verison to hrvest; H35 is hours bove 35 C; nd H30 is hours bove 30 C. The finl model ccounted for 88% (p = 0.006) of the vribility in TSMA concentrtion. Recognizing tht interreltions exist mong the four independent vribles, the model ws tested for collinerity. The condition index for the model ws 15.9. Therefore, lthough the vribles re physiclly relted, their biologicl effect on nthocynin concentrtion hd low degree of collinerity. Discussion In the present study, sunlight influenced grpe berry composition through t lest two mechnisms: temperture nd solr rdition. Visul evidence of sunburn, browning, or russeting of berry skins ws observed on clusters exposed to sunlight on the west side of north-south oriented rows. Berry tempertures exposed to sunlight on either side of the cnopy were elevted bove mbient to the sme degree. However, ctul berry tempertures were higher on sun-exposed clusters on the west side of the cnopy due to the normlly higher mbient tempertures tht occurred fter solr noon. Shded berries were t mbient temperture. Mximum berry nd mbient tempertures occurred bout 1600 hr. Vrying mgnitudes of temperture elevtion due to exposure to sunlight were reported in other studies [1,14,16,22,24,29]. With sun exposure, Smrt nd Sinclir [29] found tht the temperture of tight clusters (12.4 C) incresed bove mbient more thn loose clusters (11.1 C). They reported mximum increse over mbient of 15.7 C, while we recorded mximum increse bove mbient temperture of 12.3 C in 1999 nd 13.0 C in 2000. Merlot clusters in our study were reltively loose. For est-west oriented rows, mid-dy berry tempertures of south-exposed clusters were 3 to 4 C higher thn north-exposed clusters [1]. Sunburn hs been observed in estern Wshington on south-exposed clusters from est-west oriented rows. To support the effects of temperture nd light on phenol components, we focused in prt on some of the bsic berry mesurements (berry mss, soluble solids, TA, nd ph). Our dt regrding the effect of temperture nd light on these mesurements did not conflict with previous reports [9,14,15,18,24]. Shded nd exposed berries differed little in mss in our study even though cluster exposure tretments were imposed during stge I (pe size) of berry growth. Het stress of Np Gmy vines during Stge I nd Stge II of berry growth resulted in greter loss of berry mss thn het stress during Stge III [21]. Crippen nd Morrison [6] reported shde berries of Cbernet Suvignon were hevier nd lrger thn sun-exposed berries. Of the fruit components mesured, percent soluble solids ws perhps the lest ffected by either exposing/shding clusters from sunlight or rtificilly ltering cluster temperture. This ws in greement with Crippen nd Morrison [6], who did not differentite between est- nd west-exposed clusters. Reynolds nd coworkers [24] reported tht soluble solids of est nd west exposed clusters were higher thn prtilly nd fully shded clusters. North-exposed clusters of Cbernet Suvignon were found to hve lower soluble solids thn south-exposed clusters t given level of mid-dy PAR [1]. In generl, TA between the vrious tretments ws inversely relted to the overll temperture to which tretment ws subjected: the greter the het summtion the lower the cidity. However, preverison tem-