Research Article
Effects of water availability and pest pressures on tea
(Camellia sinensis) growth and functional quality
Selena Ahmed1,2*, Colin M. Orians2, Timothy S. Griffin3, Sarabeth Buckley4, Uchenna Unachukwu5,
Anne Elise Stratton2, John Richard Stepp6, Albert Robbat Jr.7, Sean Cash3 and Edward J. Kennelly5,8
1 Sustainable Food and Bioenergy Systems Program, Department of Health and Human Development, Montana State University,
Bozeman, MT 59715, USA
2 Department of Biology, Tufts University, Medford, MA 02155, USA
3 Friedman School of Nutrition Science and Policy, Tufts University, Boston, MA 02111, USA
4 Department of Earth Sciences, Boston University, Boston, MA 02215, USA
5 Department of Biochemistry, The Graduate Center of the City University of New York, New York, NY 10016, USA
6 Department of Anthropology, University of Gainesville, Gainesville, FL 32611, USA
7 Department of Chemistry, Tufts University, Medford, MA 02155, USA
8 Department of Biological Sciences, Lehman College, Bronx, NY 10468, USA
Received: 3 September 2013; Accepted: 16 November 2013; Published: 2 December 2013
Citation: Ahmed S, Orians CM, Griffin TS, Buckley S, Unachukwu U, Stratton AE, Stepp JR, Robbat AJr., Cash S, Kennelly EJ. 2014. Effects of
water availability and pest pressures on tea (Camellia sinensis) growth and functional quality.AoB PLANTS 6: plt054; doi:10.1093/aobpla/
plt054
Abstract. Extreme shifts in water availability linked to global climate change are impacting crops worldwide. The
present study examines the direct and interactive effects of water availability and pest pressures on tea (Camellia
sinensis; Theaceae) growth and functional quality. Manipulative greenhouse experiments were used to measure
the effects of variable water availability and pest pressures simulated by jasmonic acid (JA) on tea leaf growth and
secondary metabolites that determine tea quality. Water treatments were simulated to replicate ideal tea growing
conditions and extreme precipitation events in tropical southwestern China, a major centre of tea production. Results
show that higher water availability and JA significantly increased the growth of new leaves while their interactive
effect was not significant. The effect of water availability and JA on tea quality varied with individual secondary
metabolites. Higher water availability significantly increased total methylxanthine concentrations of tea leaves but
there was no significant effect of JA treatments or the interaction of water and JA. Water availability, JA treatments
or their interactive effects had no effect on the concentrations of epigallocatechin 3-gallate. In contrast, increased
water availability resulted in significantly lower concentrations of epicatechin 3-gallate but the effect of JA and the
interactive effects of water and JAwere not significant. Lastly, higher water availability resulted in significantly higher
total phenolic concentrations but there was no significant impact of JA and their interaction. These findings point to
the fascinating dynamics of climate change effects on tea plants with offsetting interactions between precipitation
and pest pressures within agro-ecosystems, and the need for future climate studies to examine interactive biotic and
abiotic effects.
Keywords: Camellia sinensis; catechins; climate change; herbivory;methylxanthines; precipitation; tea; total phenolic
concentrations.
* Corresponding author’s e-mail address: selena.ahmed@montana.edu
Published by Oxford University Press on behalf of the Annals of Botany Company.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/
licenses/by/3.0/), which permits unrestricted reuse, distribution, and reproduction in anymedium, provided the original work is properly cited.
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Introduction
Crops around the world are being impacted by extreme
shifts in water availability linked to global climate change.
For example, droughts and floods are reducing the yields
of many crops (Porter and Semenov 2005; Lobell et al.
2011) as well as altering their quality (Coley 1998;
Jamieson et al. 2012). In fact, precipitation is the most
important climatic determinant, along with temperature,
for plant growth and survival (Boisvenue and Running
2006). Future climatic projections show strong precipita-
tion heterogeneity depending on geographic location, in-
cluding an increase in the number of heavy precipitation
events as well as longer and more intense droughts
(Orlowsky and Seneviratne 2012; Seneviratne et al.
2012). Crop performance is further impacted by indirect
climatic influences via alterations in ecological interac-
tions such as pest pressures (Berggren et al. 2009;
Brenes-Arguedas et al. 2009; Schepp 2009). Although
the magnitude and direction of future climatic-induced
alterations to water availability remain uncertain, it is
recognized that these changes will be notable and
often exceed plant adaptive capacity (IPCC 2007).
Given present and future water availability scenarios,
research is needed to understand crop responses to
both direct and indirect effects of climate change for fu-
ture food security. While previous research has documen-
ted the impact of extreme precipitation events on crop
yields (Ewert et al. 2005; Porter and Semenov 2005;
Nelson et al. 2009; Schlenker and Lobell 2010; Lobell
et al. 2011), less is known about the direct and interactive
effects of water availability and pest pressures on crop
quality. Crop quality is largely determined by nutrient
and secondary metabolite profiles via their effects on
functional and sensory characteristics for human consu-
mers. Secondary metabolites serve as defence com-
pounds in plants that vary in concentration with a
range of environmental, genetic andmanagement condi-
tions, including water availability and pest pressures
(Herms and Mattson 1992; Glynn et al. 2007; Gutbrodt
et al. 2011, 2012; Tharayil et al. 2011; Atkinson and
Urwin 2012; Kruidhof et al. 2012; Ahmed et al. 2013).
Changes induced by both water availability and pest pres-
sures aremediated via signalling pathways (Atkinson and
Urwin 2012) that can cause an increase or decrease in the
concentrations of secondary metabolites (Gutbrodt et al.
2011; Kruidhof et al. 2012).
The present study examines the direct and interactive
effects of water availability and pest pressures on the
functional quality of tea (Camellia sinensis; Theaceae).
Tea plants, the source of the world’s most widely con-
sumed beverage after water, are geographically located
in high-risk regions for climate change. Our preliminary
work has suggested that tea functional quality drops sig-
nificantly with extreme precipitation events that accom-
pany the annual onset of the East Asian monsoon and
thatmonsoon patterns are shifting. Tea functional quality
is largely determined by polyphenolic catechin and
methylxanthine secondary metabolites that are
responsible for its antioxidant, anti-inflammatory, cardio-
protective and stimulant properties for human con-
sumers (Lin et al. 2003). Catechins and methylxanthines
are found in the highest concentrations in young expand-
ing leaves, those harvested for commercial tea, and
human consumers are able to perceive changes in the
concentrations of these metabolites by their bitterness,
astringency and sweet aftertaste (Ahmed et al. 2010).
Since the concentrations of these compounds are pre-
dicted to increase following herbivory, increasing pest
pressures during the rainy season (Coley 1998) could off-
set the effects of heavy rainfall.
In this study, manipulative greenhouse experiments
were used to measure the effects of variable water avail-
ability and pest pressures on secondary metabolites that
determine tea quality. Water treatments were simulated
to replicate ideal tea growing conditions and extreme
precipitation events in tropical southwestern China, a
major centre of tea production located in a high-risk re-
gion for climate change (Maplecroft 2011). Pest pressures
were experimentally simulated here through the applica-
tion of the plant hormone jasmonic acid (JA) to young tea
leaves (McDowell and Dangl 2000; Kruidhof et al. 2012). It
is well known that an increase in water availability can
cause an increase in growth and a decline in secondary
metabolites (Brenes-Arguedas et al. 2006); whether
simulated pest pressures would counter this response
is unknown. We hypothesized that increased water avail-
ability would indeed lead to lower concentrations of tea
secondarymetabolites, but that simulated pest pressures
would offset these direct effects of water availability.
Methods
Plant material
Tea plants (C. sinensis; Theaceae) of 2 years of age were
purchased from Logee’s Greenhouse (Danielson, CT, USA).
Plants were transplanted into 6-inch plastic pots (total
volume 1800 mL) with four drainage holes at the base
of each pot. A total of 1300 mL of soil mix that comprised
50 % pearlite and 50 %peatmosswas added to each pot.
The soil mixture was selected to facilitate quick drainage.
Plants were fertilized (Osmocote& Plus 15-9-12, Marys-
ville, OH, USA) 1 week prior to the experimental period.
A total of 120 tea plants were included in the experiment.
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Greenhouse set-up
Tea plants were maintained and treated at the green-
house facility of the Weld Hill Research Building at the
Arnold Arboretum, Harvard University (Jamaica Plain,
MA, USA). One greenhouse roomwas used for the present
experiment. Temperature, humidity and shade conditions
were selected to reflect ideal tea growing conditions.
The temperature was maintained at a range of 20–22 8C
with a humidity range of 60–70 % and steady air circula-
tion. Shade was set at 50 % over-storey density. Plants
were randomly assigned to each water availability and
pest pressure treatment and were labelled with treat-
ment identifiers. Tea plants were moved on a weekly
basis to eliminate any possible location effects within
the greenhouse.
Water availability treatments
Water availability treatments involved altering the soil
moisture content of tea plants to simulate conditions
that exist during the spring harvest in tropical south-
western China and extreme precipitation events of
drought and heavymonsoon rains (Dou et al. 2007), here-
after termed moderate water, low water and high water,
respectively. A total of 120 tea plants were treated under
each of the three water availability treatments (40 tea
plants per treatment) on the basis of field capacity of
the experimental soil mixture (32 %) as well as soil mois-
ture of field conditions at the reference location in south-
western China during mean and extreme precipitation
levels. The moderate-water treatment was maintained
at 12–16 % soil moisture content with drainage, the low-
water treatment was maintained at 4–8 % soil moisture
content with drainage and the high-water treatment was
maintained at 28–32 % soil moisture content with no
drainage. Water treatments were applied for 6 weeks
before experimental harvest to quantify leaf secondary
metabolites.
Simulated pest pressure treatments with JA
The application of JA to tea leaves was used to simulate
pest pressure on the basis of previous studies that have
shown JA application to produce induced resistance,
marked by an upregulation of secondary metabolic activ-
ity that simulates plant response by actual herbivory
leaves (McDowell and Dangl 2000; Kruidhof et al. 2012).
Using standard methods (Babst et al. 2005), half of the
plants randomly assigned to each of the three water
availability treatments were designated as having the
presence of pest pressure and treated with a solution of
0.125 % JA and 0.0625 % Triton X-100 surfactant (both
purchased from Sigma-Aldrich Co. LLC, St Louis, MO,
USA) in distilled water prior to the experimental period
and then 2 days prior to the harvest period. Triton was
added to the solution to improve the penetration of the
JA through the waxy cuticles of tea leaves. Jasmonic
acid was applied to the upper and lower surface of the
newest leaf on each branch of tea plants designated
with the presence of pest pressure. The plants designated
with the absence of pest pressure were treated with a so-
lution of 0.0625 % Triton surfactant in distilled water.
Plant growth
Growth was measured by quantifying the number of new
leaves and the height of tea plants during the experimen-
tal period.
Sample collection
A sub-sample of 40 tea plants equally representing each
of thewater availability and pest pressure treatmentswas
harvested by clipping three new leaves at their base using
sharp shearing scissors. Samples were stored on ice and
transferred to a lyophilizer (VirTis, SP Scientific) for a dry-
ing period of 48 h. Dry weights were recorded upon
removal from the lyophilizer.
Sample extraction
Leaf material was finely ground using a ball mill (Kleco
pulverizer). Twenty milligrams of pulverized leaf material
from each samplewere extracted in 1.5 mLof 80 % aque-
ous HPLC-grademethanol (Fisher Scientific). The resulting
mixture was vortexed for 30 s (Genie 2) and sonicated for
30 min at 20 8C (Quantrex 280, L&R Ultrasonics). Samples
were centrifuged following sonication for 15 min at
15 000 rpm (Marathin Micro A, Fisher Scientific) and the
supernatant was transferred to high-performance liquid
chromatography (HPLC) vials for analyses of tea quality.
Chemical analyses of tea functional quality
Tea quality was measured using HPLC to determine the
concentration of eight antioxidant polyphenol com-
pounds and three methylxanthine compounds linked to
tea functional quality, including its health claims and
stimulant properties. Individual methylxanthine com-
pounds were aggregated into a measure of total methyl-
xanthine concentrations (TMCs). In addition, total phenolic
concentrations (TPCs) of tea leaves weremeasured. High-
performance liquid chromatography was performed as
previously described to measure antioxidant polyphenol
and methylxanthine secondary metabolites (Unachukwu
et al. 2010). The polyphenols measured include catechin
(C), catechin gallate (CG), epicatechin 3-gallate (ECG), epi-
gallocatechin (EGC), epigallocatechin 3-gallate (EGCG),
gallic acid (GA) and gallocatechin 3-gallate (GCG; Chro-
maDex). The methylxanthines measured include caffeine,
theobromine and theophylline (ChromaDex). A Waters
2695 (Milford, MA, USA) module equipped with a 996
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photodiode array detector and a 4 mm, 250 × 4.6 mm ID,
C-18 Synergi Fusion, reversed-phase column (Phenom-
enex, Torrance, CA, USA) was used for the HPLC analysis.
Prior to the experimental run, the HPLC method was vali-
dated with respect to accuracy, precision, sensitivity and
selectivity. For each sample, 5 mL were injected using a
mobile phase of 0.05 % (v/v) trifluoroacetic acid in dis-
tilled water (Solvent A) and 0.05 % (v/v) trifluoroacetic
acid in acetonitrile (Solvent B). The solvent gradient was
set at a flow rate of 1 mL min21 as follows: 12–21 % Solv-
ent B from 0 to 25 min; 21–25 % Solvent B from 25 to
30 min. The column and autosampler temperatures
were maintained at 38 and 4 8C, respectively. At the
end of each run, the columnwas flushedwith 100 % Solv-
ent B for 10 min and was re-equilibrated for 5 min to
starting conditions. Spectra were recorded from 254 to
400 nm and relevant peaks were detected at 280 nm on
the basis of characteristic absorbance spectra and reten-
tion time. Analyte concentrations were determined using
peak areas and the linearity determined by plotting signal
versus concentration standard curve equations with the
limit of detection and the limit of quantification in the
ranges of 0.05–1 and 0.1–5 g mL21, respectively.
Total phenolic concentration was determined spectro-
photometrically using Folin–Ciocalteau reagent as previ-
ously described (Unachukwu et al. 2010). Samples were
analysed in triplicate. Absorbance values were measured
at 765 nm using a Benchmark Plus microplate spectrom-
eter (Bio-Rad) and results expressed as gallic acid equiva-
lents (GAE) inmg g21 dry plantmaterial. The concentration
of polyphenols in tea samples was derived from a standard
curve of GA concentration versus absorbance between
31.25 and 500 g mL21.
Statistical analysis
A fitmodel using a standard least squares means person-
ality function and analysis of variance was performed
using JMP 10.0 (SAS Institute Inc.) to determine how
leaf growth and secondary metabolite concentrations
vary among the precipitation and JA treatments. Data
were analysed for the overall effect of water availability,
JA treatment and their interactive effects. In addition, a
multiple comparison using the least squares means
Tukey’s HSD method was applied to look at the difference
between the three water availability treatments.
Results
Plant growth
Both higher water availability (P, 0.001) and JA (P, 0.001)
significantly increased the growth of new leaves while
their interactive effect was not significant (P ¼ 0.94;
Fig. 1). Overall, high-water plants had significantly more
leaves thanmoderate-water plants (P, 0.0001) and low-
water plants (P, 0.0001). The moderate-water plants
and low-water plants did not differ significantly in the
growth of new leaves (P ¼ 0.24). Tea plants under the JA
treatments had a significantly greater number of new
leaves compared with plants that were not treated with
JA (P ¼ 0.0003). Higher water availability (P ¼ 0.001) but
not JA (P ¼ 0.54) or their interaction (P ¼ 0.90) resulted
in significantly increased plant height (Fig. 2). The high–
water-availability plants had significantly greater leaf
growth than the low-water plants (P ¼ 0.001) but did not
differ significantly from the moderate-water-availability
plants (0.059). While the low-water plants differed signifi-
cantly in leaf growth from the high-water plants, they did
not differ from the moderate-water plants (P ¼ 0.22).
Chemical analyses of tea functional quality
Higher water availability (P, 0.001) significantly in-
creased TMCs of tea plants but there was no significant
effect of JA treatments (P ¼ 0.53) or the interaction be-
tween water and JA (P ¼ 0.06; Fig. 3). High-water plants
(P, 0.0217) and moderate-water plants (P, 0.0009)
had significantly higher concentrations of TMC compared
with low-water plants but did not differ significantly
from each other (P ¼ 0.41). For the concentrations of
EGCG, there was no significant effect for water availability
Figure 1. Effects of water availability and JA on leaf growth. Higher
water availability (P, 0.001) and JA (P, 0.001) significantly in-
creased the growth of new leaves while their interactive effect was
not significant (P ¼ 0.94). Values are means+1 standard error.
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(P ¼ 0.37), JA treatments (P ¼ 0.95) or their interactive ef-
fects (P ¼ 0.68; Fig. 4). Neither the low-water (P ¼ 0.28)
nor the high-water (P ¼ 0.49) treatments were signifi-
cantly different from the moderate-water plants for
EGCG concentrations. Additionally, there was no signifi-
cant difference in EGCG concentrations between high-
and low-water plants (P ¼ 0.8891). In contrast, for ECG
concentrations (Fig. 5), increased water availability (P ¼
0.02) resulted in significantly lower ECG but the effect of
JA (P ¼ 0.982) and the interactive effects of water and
JA were not significant (P ¼ 0.138). The high-water-
availability treatments had significantly greater ECG con-
centrations compared with the low-water treatments
(P ¼ 0.0117) but did not differ significantly from the
moderate-water treatments (P ¼ 0.29). While the high-
and low-water treatments differed significantly in their
ECG concentrations, the moderate-water treatment did
not differ significantly from either (P ¼ 0.29). For TPC,
higher water availability resulted in significantly higher
TPC (P, 0.0001) but there was no significant impact of
JA (P ¼ 0.89) and their interaction (0.09; Fig. 6). High-
water treatments had significantly greater TPC com-
pared with moderate-water treatments (P ¼ 0010) and
low-water treatments (P, 0.0001). Moderate-water
treatments had significantly higher TPC compared with
low-water treatments (P ¼ 0.0107).
Figure 3. Effects of water availability and JA on TMC. Higher water
availability (P, 0.001) significantly increased the TMCs of tea plants
but there was no significant effect of JA treatments (P ¼ 0.53) or the
interaction between water and JA (P ¼ 0.06). Values are means+1
standard error.
Figure 2. Effects of water availability and JA on plant height. Higher
water availability (P ¼ 0.001) but not JA (P ¼ 0.54) or their inter-
action (P ¼ 0.90) resulted in significantly increased plant height.
Values are means+1 standard error.
Figure 4. Effects of water availability and JA on the concentration of
EGCG. Higher water availability (P ¼ 0.37), JA treatments (P ¼ 0.95)
and their interactive effects had no significant effect on concentra-
tions of EGCG. Values are means+1 standard error.
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Discussion
This study supports the view that an increase in water
availability results in a significant increase in growth of
potted tea plants on the basis of both plant height and
new leaves while the effects on secondary metabolites
vary depending on chemical class. Higher water availabil-
ity increased TMCs, decreased ECG levels and decreased
TPCs of tea leaves. Epigallocatechin 3-gallate was the
only tea functional quality parameter measured that
was not significantly impacted by water availability treat-
ments. Surprisingly, pest pressures as simulated by JA
increased plant growth on the basis of new leaves, indi-
cating that potted tea plants in a greenhouse setting
may respond to pest pressures by prioritizing new leaf
growth. Unexpectedly, JA had no significant effect on sec-
ondary metabolite chemistry. However, the interactive ef-
fects of water availability and simulated pest pressures
show a trend to offset the direct effects of water availabil-
ity on TMC and TPC. These findings point to the fascinating
dynamics of climate change effects on tea plants with off-
setting interactions within agro-ecosystems and the need
for future climate studies to examine climate variables and
pest pressures as well as their interactive effects.
In general, our findings concur with previous studies
which found that altered water availability is a key driver
of plant performance (Gulati and Ravindranath 1996;
Dou et al. 2007) and significantly impacts both growth
and secondary metabolite concentrations of tea plants
(Gulati and Ravindranath 1996; Yao et al. 2005; Schepp
2009; Honow et al. 2010; CIAT 2011). Given the slow-
growing nature of woody tea plants, the less notable
effect of the treatments on plant height compared with
leaves is expected. The reduced growth of plants under
drought treatment in this study concurs with the widely
accepted recognition that lower soil moisture content
reduces photosynthesis, growth and survivability of
plants (Kozlowski et al. 1991; Condit 1998). Shrubs with
shallow roots, such as clonal tea shrubs, are particularly
susceptible to drought effects and show severe water
stress during the dry season (Tobin et al. 1997). Plants
may respond to drought by closing their stomata to re-
duce water loss at the cost of eventually facing carbon
starvation, or may keep their stomates open and face
the risk of hydraulic failure (Zeppel et al. 2011).
The variability of the response of specific secondary
metabolite concentrations to water variability empha-
sizes the complex changes in tea functional quality with
forecasted climate change and concurs with studies
showing idiosyncratic responses of individual compounds
to environmental stress (Glynn et al. 2007). Caffeine is the
primary secondary metabolite responsible for tea’s
stimulant properties and contributes to its bitter taste.
Epicatechin 3-gallate and EGCG are prominent poly-
phenolic catechins in tea that contribute to tea’s bitter
Figure 5. Effects of water availability and JA on the concentration of
ECG. Higher water availability (P ¼ 0.02) resulted in significantly
lower ECG but the effect of JA (P ¼ 0.982) and their interactive
effects were not significant (P ¼ 0.138). Values are means+1
standard error.
Figure 6. Effects of water availability and JA on TPC. Higher water
availability (P, 0.0001) resulted in significantly higher TPC but
there was no significant impact of JA (P ¼ 0.89) and their interaction
(0.09). Values are means+1 standard error.
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taste as well as its sweet aftertaste, which is highly desir-
able. In addition, these compounds contribute to its anti-
oxidant and anti-inflammatory properties and other
medicinal attributes. Total phenolic concentration and
antioxidant activity further contribute to the overall func-
tional properties of tea. Consumers can discern changes
in these compounds that influence their purchasing deci-
sions (Ahmed et al. 2010). The methylxanthine caffeine is
a nitrogen-based compound, while individual poly-
phenolic catechins along with the cumulative TPC meas-
ure represent carbon-based compounds.
We expected JA treatments to result in a large increase
in these key secondary metabolites (Karban and Baldwin
1997; Kruidhof et al. 2012). Kruidhof et al. showed that
proteinase inhibitors are highly induced by a second jas-
monate,methyl jasmonate (124 % increase). Interesting-
ly, they found that proteinase inhibitors were not
expressed in glasshouse-grown plants. They suggest
that the UV filtering properties prevent expression. Al-
though they did not induce these glasshouse-grown
plantswithmethyl jasmonate, it is possible that induction
of many compounds is dependent on light quality. We
suggest that future experiments should test the effects
of jasmonates and pest pressures on tea plants grown
in the field. Furthermore, this study used JA to simulate
pest pressures that may provide an indication of what
might happen when leaf-chewing caterpillars attack the
plant. Tea is also attacked by leaf-sucking herbivores such
as leaf hoppers, which induce different signalling path-
ways and thusmay have very different effects on tea sec-
ondary chemistry and ultimately tea quality.
The significant impact of water availability on tea func-
tional quality found in this study represents a conservative
estimate of what would happen under field conditions,
as manipulative studies are likely to underestimate plant
responses to climate change for at least two reasons
(Wolkovich et al. 2012). Field plants are exposed to many
abiotic stressors (e.g. wind) that change plant chemistry
and being older plants they typically have higher concen-
trations of many secondary metabolites. In addition, the
interaction with additional climate variables, including
temperature and carbon dioxide levels, would further ex-
acerbate complexity with opposing or enhancing effects.
In summary, future studies are needed that examine the
interactive effects of multiple climatic factors with special-
ist tea pests in both controlled and field conditions.
Conclusions
This study provides some of the first evidence on the
multi-directionality of shifts in water availability, pest
pressures and their interactive effects on tea quality.
While numerous studies have documented the impact
of climate change on crop yield, this study contributes
to the knowledge gap on climate effects on crop quality
that are crucial to examine for food security. Results indi-
cate that while extreme drought and precipitation condi-
tions might decrease or increase plant growth and
functional quality, pest pressures may offset these ef-
fects. For example, drought conditions may result in a
decline of both tea growth and stimulant properties of
tea but pest pressures may offset these effects. If the
changes in tea functional quality with water availability
and herbivore pressures are indicative of broader climate
change, tea production areas face increased heterogen-
eity with forecasted prolonged and more frequent
droughts along with increased heavy precipitation events
(Orlowsky and Seneviratne 2012; Seneviratne et al. 2012).
Future research in both controlled and natural settings
across spatial and temporal scales is needed to better
understand the interplay between a range of climatic
conditions, tea plants, herbivore pressures and other
multi-trophic interactions.
Sources of Funding
Our work was funded by a Tufts Collaborates Seed Grant,
TEACRS Program at Tufts University (NIH National Insti-
tute of General Medical Sciences IRACDA-K12GM074869),
National Science Foundation Research Experiences for
Undergraduates Program (NSF DBI 1005082) and Tufts
Institute for the Environment.
Contributions by the Authors
All authors contributed to the overall study design. S.A.
and T.G. designed water availability manipulations. S.A.
and C.O. designed simulated pest pressure treatments.
S.A. conducted greenhouse manipulations, coordinated
study logistics and harvested samples. S.A., S.B. and
U.U. were involved in the chemical and statistical analysis.
A.S. helped with the experimental set-up of the pilot
study. S.A. and C.O. primarily wrote the manuscript with
contributions from all authors.
Conflicts of Interest Statement
None declared.
Acknowledgements
We thank the Arnold Arboretum at Harvard University for
greenhouse facility use and support of this project; Angus
Schaefer for assisting with plant growth measurements;
and Amanda Kowalsick, Feven Asefaha and Matt Rey-
nolds for their work on the pilot experiments that in-
formed this study.
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