Kaolin Particle Film and Water Deficit Influence Malbec Leaf and Berry Temperature, Pigments, and Photosynthesis

Abstract

The effects of kaolin particle film on traits of commercial interest in the red-skinned winegrape cultivar Malbec (Vitis vinifera L.) were evaluated over three growing seasons by measuring the surface temperatures of leaves and clusters, leaf-level assimilation, leaf and berry pigment composition, and yield of vines grown under differing severities of water deficit with and without a foliar coating of particle film. The vines were irrigated with a standard or reduced amount of water and grown under arid field conditions with high solar radiation. Particle film increased the concentration of total monomeric anthocyanins in berries each year and the ratio of anthocyanins to soluble solids at harvest in two out of three years. The particle film did not alleviate differences in anthocyanin concentration between east-and west-exposed clusters. In vines under reduced irrigation, particle film decreased the cumulative minutes that surface temperatures exceeded 30 degrees C between mid-July through harvest in east-but not west-exposed berries and in east-exposed leaves. Leaves with particle film had lower midmorning rates of assimilation, lower chlorophyll-a to chlorophyll-b ratio, and a higher ratio of chlorophylls to carotenoids than leaves without particle film. Decreased assimilation was unrelated to the magnitude of leaf reflectance of visible light. Particle film did not affect yield components or fruit maturity, indicating that net primary productivity was sufficient to ripen fruit to maturity. These results demonstrate that foliar particle film can facilitate the accumulation of anthocyanins in deficit-irrigated Malbec under warm, arid conditions with high solar radiation.

Full text

223
Am. J. Enol. Vitic. 64:2 (2013)
Heat stress, high solar radiation, and water decit limit
production of many horticultural crops in arid climates. Solar
injury and high thermal radiation can inhibit carbon assimi-
lation and reduce fruit quality. Reective foliar lms have
been used on many crops to provide thermal protection and
to enhance water use efciency (Glenn and Puterka 2005).
Kaolin is an inert mineral with reective properties in the vis-
ible light region of the electromagnetic spectrum. Its natural
optical properties have been altered through processing to
reduce potential interference with carbon assimilation for its
use as a foliar reectant on plants.
Water decit is commonly imposed on red-skinned wine-
grape (Vitis vinifera L.) during berry development to control
canopy vigor and to enhance berry composition for red wine
production (Chaves et al. 2010). Light transmission into the
vine canopy is increased when vines are maintained under
sustained water decit and a greater surface area of leaves
and clusters in the canopy are directly exposed to incident
solar radiation (Shellie 2006). An increased incidence of heat
stress and or solar injury has been observed in arid regions
with high solar radiation when vines are maintained under a
water decit, particularly on western-exposed fruit in north-
south oriented rows and south-exposed fruit on east-west ori-
ented rows (Spayd et al. 2002).
Stomatal closure is a primary response of the leaf to water
decit and its mechanism of control varies among cultivars of
winegrape (Lovisolo et al. 2010). Transpiration is the princi-
pal avenue of heat transfer in leaves, and water-decit-related
stomatal closure has been shown to increase canopy tempera-
ture and decrease net photosynthesis (Glenn et al. 2010). The
berry is dependent on convective heat transfer since it has few
functional stomata. The inherently different mechanisms of
stomatal control among cultivars of V. vinifera would likely
inuence the effectiveness of particle lm in alleviating heat
stress. For example, particle lm reduced the canopy tempera-
ture and stomatal conductance of the cultivars Cabernet Sau-
vignon, Merlot, and Viognier under well-watered conditions,
but cultivar response differed when the vines were under a
water decit (Shellie and Glenn 2008, Glenn et al. 2010).
Many studies in eld and controlled environments have
shown that color development in red-skinned grapes is sensi-
tive to temperature and light exposure (Bergqvist et al. 2001,
Spayd et al. 2002, Yamane et al. 2006, Sadras and Moran
1Research Horticulturist, Horticu ltural Crops Research Unit, U.S. Department
of Agriculture, Agricultural Research Serv ice, 29603 U of I Lane, Parma, ID
83660; and 2Research Agricultural Engineer, Nor thwest Irrigation and Soils
Research Laboratory, U.S. Department of Agricultu re, Agricultural Research
Service, 3793 North 3600 East Kimberly, ID 83341.
*Corresponding author (email: K rista.Shellie@ars.usda.gov; fax (208) 722-
8166 )
Acknowledgments: This work was conducted under ARS project no. 5358-
21000-034- 00D entitled Production Systems to Promote Yield and Quality of
Grapes in the Pacic Northwest. The authors thank Alan Muir, Monte Shields,
and Cheryl Franklin-Miller for their techn ical assistance and the University of
Idaho Parma Research and Extension Center for the use of their eld resources
and materials.
Manuscript submit ted Sept 2012, revised Dec 2012, accepted Dec 2012
Copyright © 2013 by the American Society for Enolog y and Vit iculture. All
rights reserved.
doi: 10.5344/ajev.2012.12115
Kaolin Particle Film and Water Decit Inuence
Malbec Leaf and Berry Temperature, Pigments,
and Photosynthesis
Krista C. Shellie1* and Bradley A. King2
Abstract: The effects of kaolin par ticle lm on traits of commercial interest in the red-skinned winegrape cultivar
Malbec (Vitis vinifera L.) were evaluated over three growing seasons by measuring the surface temperatures of
leaves and clusters, leaf-level assimilation, leaf and ber ry pigment composition, and yield of vines grown under
differing severities of water decit with and without a foliar coating of particle lm. The vines were irrigated with
a standard or reduced amount of water and grown under arid eld conditions with high solar radiation. Particle lm
increased the concentration of total monomeric anthocyanins in berries each year and the ratio of anthocyanins
to soluble solids at harvest in two out of three years. The particle lm did not alleviate differences in anthocyanin
concentration bet ween east- and west-exposed clusters. In vines under reduced ir rigation, particle lm decreased
the cumulative minutes that surface temperatures exceeded 30°C between mid-July th rough harvest in east- but not
west-exposed berries and in east-exposed leaves. Leaves with particle lm had lower midmor ning rates of assimila-
tion, lower chlorophyll-a to chlorophyll-b ratio, and a higher ratio of chlorophylls to carotenoids than leaves without
particle lm. Decreased assimilation was unrelated to the magnitude of leaf reectance of visible light. Par ticle lm
did not affect yield components or fruit maturity, indicating that net primary productivity was sufcient to ripen
fruit to maturity. These results demonstrate that foliar particle lm can facilitate the accumulation of anthocyanins
in decit-irrigated Malbec under warm, arid conditions with high solar radiation.
Key words: grape, par ticle lm, heat stress, radiation stress, solar injury

224 – Shellie and King
Am. J. Enol. Vitic. 64:2 (2013)
2012). Low light conditions inhibited berry color develop-
ment (Bergqvist et al. 2001) and temperatures above 35°C
compromised the accumulation of anthocyanins in the ber ry
skin (Spayd et al. 2002).
Malbec is a red-skinned winegrape cultivar that is widely
grown in warm, arid regions with high solar radiation. Its
response to particle lm under differing soil-moisture condi-
tions has not been evaluated. The objective of this study was
to relate the decrease in leaf and surface temperature pro-
vided by the particle lm to changes of commercial interest
in the vine and berry. We hypothesized that the cooler berry
and leaf surface temperature of vines with foliar reectant
would increase berry anthocyanin content at fruit maturity
and increase water use efciency by decreasing stomatal con-
ductance and that response to particle lm would be simi-
lar but less effective under increasing water stress. In this
study, we evaluated the interactive effects of particle lm
and water decit on leaf and berry surface temperature, light
reectance, gas exchange characteristics, berry composition,
and yield of Malbec vines under eld conditions over three
growing seasons.
Materials and Methods
This eld trial was conducted in an experimental vineyard
at the University of Idaho Parma Research and Extension
Center in Parma, ID (lat: 43´78°N; long: 116´94°W; 750 m
asl) over three growing seasons (2009 to 2011). The soil at the
site was a ne sandy loam (Turbyll series) with an available
water-holding capacity of 0.14 cm/cm soil, pH 7.9, and 0.9%
organic matter. Vines of Malbec (clone 6, Foundation Plant
Services, University of California, Davis), were planted in
1997 as eight-vine panels in four replicate blocks with each
block containing three rows of 56 vines. Rows were oriented
north-south with 2 × 2.7 m vine by row spacing. The own-
rooted vines were double-trunked and each trunk was trained
to form a north- or south-facing arm of a bilateral cordon.
Cordons were spur-pruned to 16 buds per meter of cordon and
shoots were positioned vertically. Vineyard management re-
ected local commercial production practices including weed
removal and periodic application of pesticides. The eld ex-
perimental design was a split-plot with irrigation treatments
(standard or reduced) applied to main plots and particle lm
treatments (with or without) applied to subplots within four
replicate blocks.
Particle lm treatment. The particle lm (Surround WP;
Engelhard Corp., Iselin, NJ) was applied just after fruit set,
at manufacturer recommended dosage (60 g/L in 950 L/ha
aqueous suspension), in a series of three weekly applications
using a backpack sprayer as described by Shellie and Glenn
(2008). Only the rst application contained a nonionic sur-
factant (R-II; Wilbur-Ellis Agribusiness, Kennewick, WA)
at a rate of 1.3 mL/L. The foliage was sprayed until runoff
at which point the leaf surface had an even, white appear-
ance. The particle lm was applied to the entire canopy of
two vines per subplot in the rst two years of the study and
to two cluster-bearing shoots on either side of the canopy of
two vines in each subplot in the last year of the study. Vines
and shoots without particle lm served as untreated controls.
In years 1 and 2, the vines received subsequent applications
of particle lm when the white coating on the leaf surface
appeared faded or there was ~10% new growth. In year 3,
subsequent applications of particle lm were made biweekly
throughout the growing season and the reectance spectra
(200 to 700 nm at 2 nm intervals) of leaves with and without
particle lm (n = 20) under each level of irrigation were mea-
sured after each lm application (Unisys, PP Systems, Haver-
ville, MA) following a previous method (Glenn et al. 2002).
The reectance of leaves with particle lm was expressed as
the percent increase of leaves without particle lm by divid-
ing the difference in reectance by the reectance of leaves
without particle lm and multiplying by 100 and graphically
displayed (SigmaPlot 11.2; Systat Software, San Jose, CA).
Reectance of photosynthetically active radiation (PAR) was
expressed as a ratio of summed reectance counts at 430 and
660 nm of leaves with particle lm to leaves without particle
lm for each irrigation treatment level.
Irrigation treatment. Each plot had two aboveground
drip lines (16 mm i.d.; Bowsmith, Exeter, CA). One line had
embedded emitters (1.9 L/hr ow rate) at 1 m spacing (two
emitters per vine). The other line contained no emitters in
reduced irrigated plots and manually inserted emitters (3.8
L/hr ow rate) at 1 m spacing in standard irrigated plots.
Both drip lines were used during irrigation events to simul-
taneously deliver three-fold more water to standard relative
to reduced irrigated plots. The amount of water supplied to
standard irrigated plots was intended to impose a sustained,
mild water decit throughout berry development by supply-
ing ~70% of estimated crop evapotranspiration (ETc), which
is a standard industry practice in the region (Keller et al.
2008). Vines under reduced irrigation were provided 23%
of ETc. Irrigation volumes were calculated weekly using the
1982 Kimberly–Penman equation (Jensen et al. 1990) with
well-watered alfalfa as a reference crop and an on-site devel-
oped variable crop coefcient similar to that used by Keller
et al. (2008). Values for reference evapotranspiration (ETr)
were obtained from a weather station located 3 km from the
trial site (www.usbr.gov/pn/agrimet/wxdata.html). The vol-
ume of water delivered per block was measured using a ow
meter. Vine water status was monitored weekly throughout
berry development on the day preceding an irrigation event
by measuring the midday leaf water potential (Ψmd) of two,
fully expanded, exposed leaves per treatment plot using a
pressure chamber (model 610; PMS Instruments, Corvallis,
OR) as described by Shellie (2006). Effects of irrigation and
particle lm on Ψmd were determined by year and phenologi-
cal stage using a mixed model with irrigation and particle
lm as xed effects (SAS, ver. 8.02; SAS Institute, Cary,
NC). Differences between treatment means (p ≤ 0.05) were
detected using Tukey–Kramer adjusted t test. Cumulative
growing degree days (GDD) were calculated for each year of
the study using simple average daily temperature above 10°C
with no upper temperature limit with data obtained from the
same weather station used for ETr, annual precipitation, and
solar radiation.

Inuence of Particle Film and Water Decit on Temperature – 225
Am. J. Enol. Vitic. 64:2 (2013)
Berry and leaf surface temperature. The surface tem-
perature of east- and west-exposed berries was monitored
throughout development in the second year of the study and
the surface temperature of east-exposed leaves was moni-
tored in the last year of the study. Berry and leaf surface
temperatures were measured on two vines per treatment plot
in two eld blocks using infrared sensors (SI-121 Infrared
Radiometer; Apogee Instr uments, Logan, UT). Temperatures
were measured at 1-min intervals and recorded as a 15-min
average. Air temperature was measured in plots at a height of
2.5 m (HMP35C; Campbell Scientic, Logan, UT). Data from
individual sensors were averaged over replicate measurements
and cumulative minutes above 30°C were displayed graphi-
cally by treatment levels (SigmaPlot 11.2).
Berry composition and leaf physiology. The concentra-
tion of total monomeric anthocyanins in whole berries was
measured spectrophotometrically following the method of
Iland et al. (2004). Anthocyanins and juice soluble solids (SS)
were measured at harvest each season and on three sampling
dates between veraison and harvest in year 2 of the study. In
the last year of the study, berry composition at harvest was
independently analyzed by cluster aspect (east- or west-expo-
sure). Vines were harvested when a composite juice sample
from 10 clusters had ~24% SS and ~6 g/L titratable acidity
(TA). Exposed clusters collected just before harvest from ei-
ther side of the vine canopy were used for analysis of berry
anthocyanins and juice SS, pH, and TA. Yield per vine was
recorded at harvest. Berries used for anthocyanin analysis
were sampled from the top and bottom sections of east- and
west-exposed clusters and stored in a freezer at -80°C until
analysis. Juice SS, pH, and TA were determined at harvest
after crushed clusters were left on their skins overnight at
21°C, as described by Shellie (2006). Berry composition and
yield data were analyzed by year and, when appropriate, by
phenological stage or cluster-exposure aspect using a mixed
model analysis of variance with irrigation, particle lm, and
aspect as xed effects (SAS, ver. 8.02). Differences between
treatment means ( p ≤ 0.05) of signicant main effects were
detected using Tukey–Kramer adjusted t test.
The contents of chlorophyll-a (chl-a) and chlorophyll-b
(chl-b) and carotenoids in leaves on primary shoots located
between nodes 7 and 12 were measured on three sampling
dates during berry ripening in the first year of the study.
Preliminary extractions were performed to ensure that the
particle lm residue did not interfere with pigment quantica-
tion. Leaf samples were rinsed and pigments extracted from
six leaf discs (1 cm2) per treatment plot following the method
of Steele et al. (2009). Absorption spectra of the supernatant
were recorded at 468, 652, and 665 nm (Beckman DU 520
UV/Vis Spectrophotometer; Beckman, Fullerton, CA), and
chl-a, chl-b, and carotenoid contents were quantied using
published absorption coefcients (Lichtenthaler 1987). Pig-
ment content was expressed as a function of leaf area.
The transpiration (E), photosynthesis (ACO2), and stomatal
conductance (gs) of an east-exposed leaf in each subplot (n
= 4) was measured at midmorning (10:00 to 12:00 MDT) at
biweekly intervals between weeks 29 and 35 using a CIRAS-2
Photosynthesis System (PP Systems, Amesbury, MA) in the
last year of the study. Cuvette flow was 400 mL/min and
contained 388 mg/L CO2. An LED light source provided 1200
μmol m2/s inside the cuvette. Intrinsic water use efciency
(WUE) was calculated as the ratio of ACO2 to gs. Assimilation
of leaves with particle lm was expressed as a ratio of leaves
without particle lm for each irrigation treatment level. The
relationship between leaf reectance and ACO2 was analyzed
by regression of the PAR and assimilation ratios using Sigma-
Plot 11.2. Leaf pigments and gas exchange data were analyzed
by sample date using a mixed model analysis of variance
with irrigation and particle lm as xed effects (SAS, ver.
8.02). Differences between treatment means ( p ≤ 0.05) were
detected using Tukey–Kramer adjusted t test.
Results
Growing season environmental conditions. Accumu-
lated GDD was highest in year 1, lowest in year 3, and on
the low end of average in year 2 (Table 1). Growing season
precipitation was similar to the site average in year 1 and 2
and higher than average in the year 3. There were fewer than
average number of days with maximum temperatures that
exceeded 35°C in all years even though daily average total
direct solar radiation was similar each year to the 15-yr site
average. Seasonal ETr was similar to the site average in the
rst and third years, but lower than average in the second
year. The amount of water delivered to plots under standard
irrigation supplied 34, 27, and 32% of growing season ETr in
the rst, second, and third years, respectively. Plots under
reduced irrigation received 33% the amount of standard ir-
rigated plots in each study year.
Table 1 Weather parameters 1 Apr through 31 Oct collected from Bureau of Reclamation Agrimet Parma, Idaho, weather station
and irrigation amount applied under standard and reduced treatments. Accumulated growing degree days were calculated from daily
maximum and minimum temperature with no upper limit and a base temperature of 10°C.
Parametera2009 2010 2011 1994–2009
Accumulated GDD (°C) 1800 1689 1597 1723 ± 115
Days daily maximum temp >35°C 15 12 19 30 ± 12
Daily average total direct solar radiation (MJ m-2)20.8 21.9 21.9 22.1 ± 0.9
Precipitation (mm) 111 105 142 98.2 ± 36
Alfalfa-based ETr (mm) 1202 1158 1198 1218 ± 51
Standard irrigation (mm) 405 321 383 _
Reduced irrigation (mm) 135 107 128 _
aGDD: growing degree days; ETr: reference evapotranspiration.

226 – Shellie and King
Am. J. Enol. Vitic. 64:2 (2013)
The particle lm had no consistent inuence on Ψmd under
standard or reduced irrigation (Table 2). The Ψmd of vines
under reduced irrigation was more negative pre- and post-
veraison than in vines under standard irrigation in each year
of the study and was lowest in year 1. The average difference
in Ψmd between vines under standard and reduced irrigation
was ~0.26 MPa before veraison and ~0.40 MPa between ve-
raison and harvest.
Berry surface temperature and composition. Particle
lm reduced the cumulative number of minutes the surface
temperatures of east-exposed berries exceeded 30°C but had
no statistical effect on west-exposed berries under reduced
irrigation (Figure 1). West-facing berries under reduced ir-
rigation accumulated the most temperature minutes. East-ex-
posed berries with particle lm began accumulating less tem-
perature minutes around veraison (23 Aug) under standard
irrigation and about four weeks later (20 Sept) under reduced
irrigation. Under standard irrigation, west-exposed berries
with particle lm began accumulating fewer temperature
minutes about two weeks later than east-exposed berries.
Table 2 Midday leaf water potential between fruit set and veraison (Pre) and veraison to harvest (Post) of Malbec vines grown in Parma,
Idaho, under standard or reduced irrigation, with or without a foliar application of particle film (PF). Values are the average of weekly mea-
surements. PF was applied to the entire vine canopy in 2009 and 2010 and to east- and west-exposed shoots in 2011.
Midday leaf water potential (MPa)a
2009 2010 2011
Pre Post Pre Post Pre Post
Standard irrigation -1.04 -0.92 -0.80 -0.79 -0.80 -0.86
Reduced irrigation -1.30 -1.32 -1.07 -1.13 -0.95 -1.28
Irrigation (IRR) ** ** ** ** ** **
Particle film (PF) ns ns ns ns ne ne
IRR × PF ns ns ns ns ne ne
aWithin column treatment least square means significantly different according to Tukey-Kramer adjusted t test. ** indicates significance at p ≤
0.01 and ns indicates not significant; ne: not evaluated.
Figure 1 Cumulative minutes berry surface temperature exceeded 30°C in east- (A and B) and west- (C and D) exposed clusters of Malbec on vines
irrigated with a reduced or standard amount of water, with (+PF) or without (-PF) a foliar application of particle lm during the 2010 growing season in
Parma, Idaho. Symbols represent average of two sensors each located on a different cluster and bars indicate standard error of the mean.

Inuence of Particle Film and Water Decit on Temperature – 227
Am. J. Enol. Vitic. 64:2 (2013)
Standard measurement error was greater under reduced ir-
rigation than under standard irrigation.
Particle lm had no detectable inuence on berry maturity
indices at harvest (SS, pH, or TA), cluster number, yield per
vine, or berry fresh weight. Irrigation amount affected all of
these attributes except cluster number. Vines under reduced
irrigation had lower yield and berry fresh weight than vines
under standard irrigation. Yield per vine each sequential year
was 6.0, 4.2, and 7.4 kg under standard irrigation and 5.4, 3.0,
and 5.3 kg under reduced irrigation. Berry fresh weight each
sequential year was 1.7, 1.5, and 1.8 g under standard irriga-
tion and 1.4, 1.3, and 1.6 g under reduced irrigation. Vines
had an average of 37, 39, and 53 clusters under standard ir-
rigation and 36, 33, and 42 clusters under reduced irrigation
each sequential year. Berries under reduced irrigation had
higher SS and lower TA than berries under standard irriga-
tion. Berr y SS at harvest for each sequential year of the study
was 23.5, 23.2, and 22.9 under standard irrigation and 24.1,
24.3, and 23.8 under reduced irrigation. Berry TA was 4.5,
7.0, and 8.7 g/L under standard irrigation and 3.8, 5.4, and
7.5 g/L under reduced irrigation.
Particle lm increased berry anthocyanins at harvest by
20% in 2009 (from 1.78 to 1.98 mg/g), 10% in 2010 (from
2.51 to 2.76 mg/g), and 9% in 2011 (from 2.31 to 2.51 mg/g).
Particle lm also increased the ratio of anthocyanins to SS at
harvest by 7, 9, and 8% in each sequential year of the study
(Table 3). In 2010, particle lm increased this ratio by 31%
at veraison and 14% between veraison and harvest. In 2011,
particle lm increased the ratio of anthocyanins to SS at har-
vest in east- but not west-exposed berries.
Leaf surface temperature, reflectance, gas exchange,
and pigments. Particle lm reduced the cumulative number
of minutes the surface temperatures of east-exposed leaves
exceeded 30°C but had no statistical effect on the cumulated
temperature minutes of leaves under standard irrigation (Fig-
ure 2). Under reduced irrigation, leaves with particle lm accu-
mulated less temperature minutes than leaves without particle
lm from around mid-August (before veraison) until harvest.
Leaves with particle lm had lower intrinsic WUE than
leaves without particle lm on two out of ve sampling dates
(Table 4). The ACO2 of leaves with particle lm on 25 July,
18 Aug, and 6 Sept were 5.3, 10.0, and 10.8 µmol CO2 m2/s,
respectively, and without particle lm were 8.2, 12.1, and 12.9
µmol CO2/m2/s, respectively. Leaves with particle lm had a
lower ratio of chl-a to chl-b and a higher ratio of chlorophyll
to carotenoids than leaves without particle lm (Table 4).
Particle lm decreased leaf carotenoids under standard ir-
rigation but increased carotenoids under reduced irrigation.
Leaves with particle lm had two- to nine-fold greater re-
ectance in the UV-A (315 to 400 nm) and visible (400 to 700
nm) wavelengths (Figure 3A), and reectance increased with
Table 3 Ratio of anthocyanins to soluble solids (SS) in Malbec berries harvested at different phenological stages from east- and
west-exposed clusters on vines grown in Parma, Idaho, under standard or reduced irrigation, with (+) or without (-) a foliar application
of particle film (PF).
Anthocyanin to SS ratio (mg/g fresh wt/Brix*100)a
2009 2010 2011
Harvest Veraison Postveraison Harvest
Harvest
East West
Standard, +PF 8.05 4.02 9.34 11.28 11.02 10.61
Standard, -PF 7.57 2.79 9.15 11.04 10.42 9.60
Reduced, +PF 8.23 4.35 10.15 11.67 11.29 9.03
Reduced, -PF 7.73 3.60 8.90 9.97 10.57 8.57
Irrigation (IRR) ns *ns ns ns *
PF ns ** ** * * ns
IRR × PF ns ns *ns ns ns
Aspect (A) ne ne ne ne **
IRR × A ne ne ne ne *
PF × A ne ne ne ne ns
IRR PF × A ne ne ne ne ns
aMean values multiplied by 100. Within column treatment means are significantly different according to Tukey-Kramer adjusted t test. *, **, and
ns indicate significance at p ≤ 0.05, p ≤ 0.01, and ns not significant, respectively; ne: not evaluated.
Figure 2 Cumulative minutes east-exposed leaf surface temperature
exceeded 30°C on vines of Malbec irrigated with a reduced or standard
amount of water, with (+PF) or without (-PF) a foliar application of par-
ticle lm during the 2011 growing season in Parma, Idaho. Symbols
represent average value of four leaves from two vines and bars indicate
the standard error of the mean.

228 – Shellie and King
Am. J. Enol. Vitic. 64:2 (2013)
sequential lm applications through 18 Aug. Leaf reectance
was highest on the 18 Aug and 6 Sept where reectance at
430 and 680 nm was at least ve-fold greater on leaves with
particle lm than without particle lm. The high frequency
of assimilation ratios less than one show that particle lm
decreased leaf assimilation regardless of irrigation treatment
and sampling date (Figure 3B). PAR assimilation ratios below
one occurred with equal frequency when PAR reectance was
increased two- to 10-fold across sampling dates and irrigation
treatment levels.
Discussion
The ratio of anthocyanins to soluble solids (SS) in wine-
grape is of commercial interest because it inuences the qual-
ity potential of red wine. Warming trends in winegrape pro-
duction regions have been associated with a decreased ratio of
anthocyanins to SS in mature fruit (Sadras and Moran 2012).
Particle lm increased the ratio of anthocyanins to SS in this
study by increasing the content of anthocyanins. Unlike the
response of Viognier (Shellie and Glenn 2008), particle lm
did not affect the SS concentration of Malbec. The observed
increase in anthocyanin content implies that the amount of
light transmitted through the particle lm to the berry surface
was sufcient to meet light requirements for color develop-
ment (Bergqvist et al. 2001, Spayd et al. 2002).
The increase in anthocyanin concentration of berries with
particle lm was most likely the result of cooler berry surface
temperatures. Real-time PCR and 13 C stable isotope tracer
were used to show reduced biosynthesis and increased deg-
radation of anthocyanins in Cabernet Sauvignon exposed to
35°C air (Mori et al. 2007). Yamane et al. (2006) determined
that the rst two weeks after veraison was the phenological
stage most sensitive to high temperature inhibition (30°C) in
the cultivar Aki Queen. The temperature we measured at the
surface of exposed berries at the canopy exterior was most
likely warmer than at the canopy interior because the particle
lm reduced the total amount of radiation transmitted into the
vine canopy. Thermal imaging of apple (Malus sylvestris) tree
Figure 3 Different shaped symbols signify sampling date after sequen-
tial lm application in 2011. Percent increase in reectance of leaves
with particle lm (A); symbols are the average value (n = 16) of leaves
sampled from eight vines and bars indicate the standard error of the
mean. Relationship between the calculated PAR and assimilation ratios
of leaves with particle lm relative to leaves without particle lm under
standard (open symbols) or reduced (closed symbols) irrigation (B);
symbols indicate sampling date.
Table 4 Leaf level, intrinsic water use efficiency (ACO2/gs), and leaf chlorophyll (Chl) and carotenoid (Crt) content in east-exposed leaves
of Malbec with (+) or without (-) a foliar coating of particle film (PF) on vines under standard or reduced irrigation measured midmorning at
sampling intervals beginning around veraison.
ACO2/gs (µmol CO2/mol H2O)aLeaf pigmentsa,b
25 July 8 Aug 18 Aug 6 Sept 19 Sept
Chl-a
(µg/cm2)
Chl-b
(µg/cm2)
Crt
(µg/cm2)
Chl-
a/b
Chl/
Crt
Standard +PF 15.3 54.1 28.8 38.5 29.9 37.94 11.90 11.46 3.22 4.37
Standard –PF 28.4 56.6 32.1 43.8 32.0 38.68 11.44 12.49 3.38 4.05
Reduced +PF 17.2 57.2 29.4 42.5 37.8 40.08 12.55 12.52 3.20 4.25
Reduced -PF 23.1 55.4 47.7 51.3 34.5 37.71 11.58 12.10 3.28 4.09
Irrigation (IRR) ns ns ns ns ns ns ns ns ns ns
PF ns ns * * ns ns ns ns * *
IRR × PF ns ns ns ns ns ns ns ** ns ns
Air (°C)c30.4 25.3 25.2 23.9 20.2
VPD (kPa)c3.5 2.4 2.8 1.9 1.4
aWithin column treatment means are significantly different according to Tukey-Kramer adjusted t test. *, **, and ns indicate significance at p ≤
0.05, p ≤ 0.01, and ns not significant, respectively; ne: not evaluated.
bPooled mean of 29 July, 18 Aug, and 1 Sept 2009 sampling dates.
cAverage air temperature and vapor pressure deficit between 10:00 and 12:00 MDT in 2011.

Inuence of Particle Film and Water Decit on Temperature – 229
Am. J. Enol. Vitic. 64:2 (2013)
canopies showed that trees with a foliar particle lm coat-
ing had a distribution of cooler temperatures throughout the
canopy (Glenn 2009). It is therefore possible that the particle
lm coating provided a cooler microclimate throughout the
vine canopy.
In this study, particle lm and reduced irrigation increased
the ratio of anthocyanins to SS at veraison, when average SS
was 16.7%. The increased ratio was of statistical signicance
at harvest only in vines with particle lm, particularly in east-
exposed clusters. Sadras and Moran (2012) investigated the
inuences of temperature, water decit, and source to sink
relationships on the accumulation rates of SS and anthocya-
nins in Shiraz and Cabernet franc and found that anthocyanin
accumulation was independent of SS accumulation until SS
reached ~11.4%, after which accumulation was linear and
parallel. They found that elevated air temperature delayed the
onset of anthocyanin accumulation without changing the lin-
ear phase accumulation rate, whereas water decit increased
the linear phase accumulation rate without changing the onset
of accumulation. The high level of SS at the time of the rst
sampling in this study prohibits speculation as to whether the
particle lm or water decit altered onset and or accumulation
rates; however, the sustained increased ratio in berries with
particle lm suggests that cooler berry surface temperature
altered the balance between rates of biosynthesis and degra-
dation during ripening. The postveraison interaction between
particle lm and irrigation amount could be explained by the
alleviation of water-decit-associated increases in berry tem-
perature by the particle lm. Water decit-induced increases
in anthocyanins at veraison were likely offset by subsequent
temperature-related changes in rates of biosynthesis, or deg-
radation. The striking difference in anthocyanin concentra-
tion between east- and west-exposed berries in vines under
reduced irrigation exemplify the trade-off between the puta-
tive benet of enhanced accumulation and the need to main-
tain water supply for evaporative cooling and protection from
extreme temperature. A similar additive effect of water decit
and exposure aspect on berry color in Merlot and Cabernet
Sauvignon has been reported (Shellie 2011). Results from this
study suggest that the particle lm coating facilitated the in-
uence of water decit to enhance berr y color.
Particle lm increased the reectance of solar radiation at
UV-A and visible light wavelengths, as reported elsewhere
(Glenn et al. 2002, Jifon and Syvertsen 2003). We observed
a decreased rate of ACO2 in leaves with particle lm that was
unrelated to the magnitude of reflectance by the particle
lm coating on the leaf surface, sampling date, and irriga-
tion amount. The presence of particle lm on the leaf sur-
face, even at low levels of reectance, was associated with
a decrease in ACO2. Since we observed no detectable effect
of the particle lm on gs, the decrease in intrinsic WUE of
leaves with particle lm was due to a decrease in ACO2. The
change in gs associated with particle lm in grapefruit (Citrus
paradisi L.), leaves (Jifon and Syvertsen 2003), apple (Glenn
2009), and other grape cultivars (Shellie and Glenn 2008,
Glenn et al. 2010) was not evident in Malbec under the con-
ditions of this study, suggesting that the decrease in Malbec
leaf surface temperature was due to reection of thermal ra-
diation rather than enhanced transpirational cooling. Warmer
leaf surface temperature of vines under reduced relative to
standard irrigation was also reported in eld-grown vines of
Cabernet Sauvignon (Glenn et al. 2010).
The similar yield and berry maturity indices we observed
in vines of Malbec with or without particle film suggests
that decreased ACO2 did not limit the capacity of the vine
to ripen fruit to maturity. The cooler canopy of vines with
particle lm would likely reduce the total amount of carbon
consumed in respiration, and respiration was found to have
a major inuence on total carbon balance (Escalona et al.
2012). The pigment changes we observed in Malbec leaves
with particle lm could also partially explain why decreased
ACO2 did not limit vine productivity or fruit maturity. Glenn et
al. (2003) found no change in the pigment content of mature
Empire apple leaves coated with particle lm, but Pallioti et
al. (2000) noted a similar difference in pigment composition
between sun-exposed (PPFD 1500-1600 µmol photons m2/s)
and shaded (3 to 5% of full sunlight) leaves. Shaded leaves
had increased contents of chl-a, chl-b, and carotenoids and
a lower ratio of chl-a to chl-b. Pallioti et al. (2000) reported
higher quantum yield in shaded versus sun-exposed leaves
and speculated that the pigment changes in shaded leaves en-
hanced photochemical use efciency by better utilizing low-
energy and far-red radiation (photosystem I) and increased
total light harvesting capacity.
Conclusions
The objective of this study was to relate the decrease in
leaf and berry surface temperature provided by the particle
lm to changes of commercial interest in the vine and berry.
Results supported our original hypothesis that ber ries from
vines with foliar reectant would have a greater concentration
of anthocyanins at fruit maturity. The increase in anthocyanin
to SS ratio appeared to be associated with a reduction in sur-
face temperatures and reduced transmission of radiation into
the vine canopy. The particle lm did not decrease stomatal
conductance or increase the intrinsic WUE of Malbec, as we
had expected from prior research with the cultivars Caber-
net Sauvignon, Merlot, and Viognier. Instead, we found that
particle lm decreased the intrinsic WUE of Malbec due to
a decrease in photosynthesis that was unrelated to the mag-
nitude of reectance of visible light from the leaf surface.
We observed a change in the pigment content of leaves with
particle lm that was similar to reported changes in pigment
content of shaded leaves and speculated that pigment changes
and decreased respiration due to cooler surface temperatures
partially explained why decreased photosynthesis did not ad-
versely affect yield components or fruit maturity. Response to
particle lm was similar in vines under standard and reduced
irrigation, but the decrease in berry and leaf surface tempera-
ture with particle lm was greater under reduced than under
standard irrigation. Our results suggest that that foliar particle
lm can facilitate the inuence of water decit to enhance
the berry color of Malbec under warm, arid conditions with
high solar radiation.

230 – Shellie and King
Am. J. Enol. Vitic. 64:2 (2013)
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