Water Deficit Affects Plant and Soil Water Status, Plant Growth,

and Ginsenoside Contents in American Ginseng

Jinwook Lee1,2*

and Kenneth W. Mudge1

1Department of Horticulture, Cornell University, Ithaca, NY 14853, U.S.A.

2USDA-ARS, Tree Fruit Research Laboratory, 1104 N. Western Ave., Wenatchee, WA 98801, U.S.A.

*Corresponding author: jl425@cornell.edu, Jinwook.Lee@ars.usda.gov

Received July 4, 2013 / Revised September 4, 2013 / Accepted November 27, 2013

Korean Society for Horticultural Science and Springer 2013

Abstract. American ginseng (Panax quinquefolius L.) produces pharmacologically active secondary compounds known

as ginsenosides which have been shown to be influenced by both genetic and environmental factors. In a greenhouse

experiment, effects of water deficit on ginseng plant growth, predawn leaf water potential ( Leaf), soil water potential

( Soil), leaf abscisic acid (ABA) concentration, and root ginsenoside contents as well as photosynthesis-related

physiological responses were studied. Three-year-old seedlings, grown in 200 mL volume of plastic pots, were well

watered for 45 days prior to the initiation of water deficit treatments. Plants in the water deficit treatments were irrigated

every 10 or 20 days for the mild and severe water deficit treatments, respectively, while the control plants were watered

every 4 days. The experiment was terminated after 15, 6, and 3 dry down cycles (60 days) for the control, mild,

and severe water deficit treatments, respectively. As water deficit progressed, both Soil and Leaf decreased, but foliar

ABA concentration increased. Other physiological responses to water deficit, including transpiration rate, stomatal

conductance, and CO2 assimilation rate, were decreased. Water deficit decreased root growth, but unaffected shoot

growth. Foliar chlorophyll content was also decreased in the water deficit treatments. The contents of individual

ginsenosides Re, Rb1, Rc and Rd, and total ginsenosides were increased in the storage roots of water deficit-treated

plants as compared with well-watered controls. Rootlet fresh weight before transplanting (RFWBT) as a covariate had

a significant effect on the contents of ginsenoside Rb1, Rc, and Rb2. Overall, the results indicate that water deficit

could contribute not only to reducing plant performance but also increasing the levels of ABA and certain ginsenoisdes.

Additional key words: abscisic acid (ABA), drought stress, evapotranspiration, leaf water potential, Panax

quinquefolium L., soil water potential

Hort. Environ. Biotechnol. 54(6):475-483. 2013.

DOI 10.1007/s13580-013-0090-2

ISSN (print) : 2211-3452

ISSN (online) : 2211-3460

Research Report

Introduction

American ginseng (Panax quinquefolius L.), belonging to

Araliaceae family, has been widely produced in North

America for use in both the West and in Asia for medicinal

purposes which are associated with the pharmaceutically

active secondary constituents known as ginsenosides (Attele

et al., 1999). The compositions and contents of individual

ginsenosides are influenced by both genetic (population)

and environmental (location) factors (Lim et al., 2005).

Assinewe et al. (2003) also reported population difference in

ginsenoside accumulation among ten geographically isolated

wild populations. The compositions and contents of gin-

senosides were also affected by numerous environmental

factors, including understory light levels (Fournier et al.,

2003), soil mineral nutrients (Konsler et al., 1990; Lee and

Mudge, 2013; Li and Mazza, 1999), plant growth regulators

(Barbara et al., 2006), elevated temperatures (Jochum et al.,

2007), and water stress (Lim et al., 2006).

Intensive field production of ginseng involves using an

artificial shade and irrigation (Li, 1995). Woods cultivation

is an alternative production system involving natural forest

shade of deciduous hardwood tree species (Beyfuss, 1999).

Unlike field cultivation, irrigation is not practiced and ginseng

is in competition with trees for soil moisture. Therefore,

water deficit stress may have a significant impact on ginseng

growth and ginsenoside accumulation. Li and Berard (1998)

demonstrated that reduced soil moisture levels decreased

root fresh weight (FW) and dry weight (DW) and root

diameter. Under the condition of water deficit, the emergence

of shoots and subsequent root fresh weight of Asian ginseng

(Panax ginseng C.A. Meyer) were decreased (Mork et al.,

Jinwook Lee and Kenneth W. Mudge476

1981). Moreover, reduced soil moisture managed by elevating

ginseng beds in Asian ginseng adversely affected net photo-

synthetic activity and transpiration rate (Lee et al., 1982).

Lim et al. (2006) demonstrated that the moderate water

stress increased the contents of certain individual and total

ginsenosides, but did not affect plant growth of American

ginseng.

Water deficit effects on gas exchange and abscisic acid

(ABA) accumulation have been well documented for many

horticultural and agronomic crops (Clemente and Marler,

1996; Delfine et al., 2002; Ennahli and Earl, 2005; Wang et

al., 2004). When available water is limited, ABA concen-

tration is elevated causing stomatal closure (Alves and

Setter, 2000; Wang et al., 2004). Photosynthesis and tran-

spiration are reduced by water deficit in cassava (Manihot

esculenta Crantz) (Alves and Setter, 2000) and sweet potato

(Ipomoea batatas Lam.) (Haimeirong and Kubota, 2003)

which have storage root systems similar to ginseng. Fur-

thermore, reduced soil moisture causes reduced quantum

yield of PSII in sweet potato (Haimeirong and Kubota, 2003)

and correspondingly decreased sink capacity. During the

growing season, the elevated temperatures decreased net

photosynthetic rate and stomatal conductance of American

ginseng plants cultivated in a greenhouse (Jochum et al.,

2007). However, there are no such reports of the effect of

water deficit on CO2 assimilation and ABA accumulation in

American ginseng. Therefore, the objectives of this experiment

were to test the hypothesis that water deficit treatment would

reduce American ginseng growth, decrease photosynthetic

activity, while increasing ABA concentration, and thereby

influence the compositions and contents of individual and

total ginsenosides. This information will be useful to under-

standing the physiological responses of American ginseng

to water deficit.

Materials and Methods

Three-year-old American ginseng (Panax quinquefolius

L.) rootlets were grown on a bed under the natural shade of

deciduous trees at a local ginseng forest farm in upstate New

York, U.S.A., harvested in November 2004, then transported

and stored at 4°C for 12 weeks in Ithaca, New York, U.S.A.

A greenhouse potting mixture, consisting of 1: 2: 1; soil:

peat : perlite by volume, was fully air-dried for 10 days in a

greenhouse. Four hundred grams of the air-dried potting

mixture was added to 200 mL volume of plastic pots (13 cm

top diameter, 8.8 cm bottom diameter, and 11.5 cm depth)

in which ginseng rootlets were planted. Fresh weight of

each rootlet was recorded and then transplanted into the

plastic pots containing the greenhouse potting mixture. The

experiment was laid out in a completely randomized design

with 60 replications (individual pots) per treatment. All

plants were well watered every other day for the first 45

days before initiation of water deficit treatments. The water

deficit treatments consisted of 4, 10, and 20 days of dry

down interval for the control, mild, and severe water deficit

treatments, respectively. Experimental irrigation was repeated

for 15, 6, and 3 dry down cycles for the control, mild water

deficit, and severe water deficit treatments, respectively,

over a 60 days period. The potted rootlets were maintained

under 70% shade with a polypropylene shade cloth in a

greenhouse at 20 ± 2°C with a below-bench evaporative

cooling system. Lighting from 60 W incandescent bulbs was

progressively adjusted to approximate natural growing

season photoperiod.

Ginseng plants were harvested after 105 days of greenhouse

cultivation, approximating the length of the normal growing

season in the field. After measuring shoot growth charac-

teristics, including prong number, leaflet number, and sym-

podium height, plants were dug to harvest roots for the

evaluation of root growth characteristics and ginsenoside

contents. After that, shoot FW, leaf area, root length, root

diameter, and root FW were measured. Before transplanting

to 200 mL plastic pots at the beginning of the water deficit

experiment, rootlets were weighed for rootlet fresh weight

before transplanting (RFWBT), total root length (the sum of

storage root length and the longest fibrous root length), and

root diameter were measured. The same root growth parameters

were measured after roots were harvested at the end of the

water deficit experiment. The percentage change in each

root growth (RG) parameter based on root fresh weight was

calculated using the following formula:

Root Growth Rate (%) =(RGAH - RGBT)

× 100RGBT

where the AH and BT stand for after harvesting (end of

experiment) and before transplanting (beginning), respectively.

The harvested ginseng root samples were placed on a forced-

air food dehydrator (American Harvest Forced Air Food

Dehydrator FD 50/30, NESCO®, Milwaukee, Wisconsin,

U.S.A.) at 35°C for 7 days before measuring root DW, and

subsequent analysis of root ginsenoside contents. Leaf area

was measured with a leaf area meter (LI-3100, LI-COR, Inc.,

Lincoln, Nebraska, U.S.A.) and then shoot tissues were oven

(1321F SHEL LAB Forced Air Ovens, Sheldon Manufacturing,

Inc., Cornelius, OR, U.S.A.) dried at 70°C for 3 days for the

measurement of shoot DW. All plants from each treatment

were 24 plants (n = 24).

During the water deficit experiment, the volumetric soil

moisture content ( ) was recorded daily using a Theta probe®

Hort. Environ. Biotechnol. 54(6):475-483. 2013. 477

(Delta-T Devices Ltd., Cambridge, U.K.). Soil water potential

( Soil) was calculated from using the regression equation

between and Soil (n = 24) determined psychrometrically

as described by Reaves (2003). Predawn leaf water potential

( Leaf) was measured on the largest (central) leaflet of a

compound leaf with a pressure bomb (Soil Moisture Equip-

ment Co., Santa Barbara, CA, U.S.A.) on five individual

plants per treatment (n = 5). Daily evapotranspiration was

calculated by subtracting pot weight day by day from initial

pot weight (n = 24).

At the end of the water deficit experiment, leaf gas

exchange was measured on the biggest leaflet located in the

middle of a compound leaf chosen for sampling on 10 plants

per treatment (n = 10) using a portable steady state gas-

exchange system (CIRAS-I, PP Systems, Herts, U.K.) at

ambient CO2 (360 mol·mol-1

). The gas exchange measure-

ments were taken in random order to compensate for any

effects caused by sampling time from 1000 to 1100 HR.

Leaf temperature within the cuvette was controlled at 20 ±

0.5°C and photosynthetic photon flux density (PPFD) was

maintained at 550 ± 50 mol·m-2

·s-1

. After the measurement

of gas exchange, leaf chlorophyll was extracted with 80%

(v/v) acetone from 10 plants per treatment (n = 10), and

absorbance was measured at 663 nm and 645 nm. The

contents of chlorophyll a, b and a + b were calculated as

described by Arnon (1949).

For ABA analysis, at the end of the water deficit ex-

periment, a 1 cm diameter leaf disc was taken by a cork

borer, placed into 250 L ice-chilled solution of 80% (v/v)

ethanol, and then stored at -20°C freezer until ABA analysis.

The ABA analysis was performed by using enzyme-linked

immuno-sorbent assay (ELISA) as described by Alves and

Setter (2000) with the slight modification that ABA extracts

were finally incubated in 200 L of 0.9 M diethanolamine

(DEA) buffer with 0.2 g para-nitrophenylphosphate (PNPP)

for 150 min at room temperature before measurement.

The analysis of root ginsenoside contents followed Lee

and Mudge (2013). One hundred milligrams dried ground

ginseng root tissue which was screened with a 60 mesh was

extracted in 30 mL of 70% (v/v) MeOH. The MeOH extract

was vacuum-evaporated at 38°C with a rotary evaporator

(Buchi 011, BUCHI Analytical Inc., New Castle, DE, U.S.A.),

redissolved in 5 mL of 100% MeOH and dried with a rotary

evaporator (Buchi 011, BUCHI Analytical Inc., New Castle,

DE., U.S.A.). The residue was redissolved in 500 L of

16% acetonitrile before injection of 15 L into the HPLC.

The HPLC system for ginsenoside analysis was a Waters

2690 Separations Module HPLC with Waters 996 Photodiode

Array Detector at 203 nm. Empower Pro software (Build

1154, Waters Co., Milford, MA, U.S.A.) was used for the

solvent gradient and peak identification and integration. The

reversed phase C18 column (Varian HPLC Columns, Varian

Inc., Lake Forest, CA, U.S.A.) was used with a guard column

(Reversed Phase ChromSep Guard Column SS, Varian Inc.,

Lake Forest, CA, U.S.A.). A gradient of the eluents (A)

0.14% phosphate buffer and (B) 100% acetonitrile was used

as follows: 0-20 min, 84-82% A, 16-18% B; 20-60 min,

82-60% A, 18-40% B. The flow rate was 1.15 mL·min-1

. As

an internal standard, m-cresol (Sigma Chemical Co., St. Louis,

MO, U.S.A.) was added into each sample to confirm the

injection volume and retention time per injection. Individual

ginsenosides from the extracts were identified and quantified

by retention time and peak areas as compared with those of

authentic ginsenoside standards Rg1, Re, Rb1, Rc, Rb2, and

Rd (Indofine Chemical Co., Hillsborough, NJ, U.S.A.).

Each dependent variable (plant growth characteristics, leaf

chlorophyll content, gas exchange, ABA concentration, and

root ginsenosides) was statistically analyzed using the analysis

of variance (version 8.02; SAS Institute, Cary, NC, U.S.A.).

Rootlet fresh weight before transplanting (RFWBT) was used

as a covariate to evaluate variation among treatments. Fol-

lowing analysis of variance, mean separation was performed

by Duncan’s multiple range tests at 5% level.

Results

At the end of the water deficit experiment, shoot growth

was not significantly affected by water deficit treatment

except for leaf area per plant (Table 1). Leaf area in the mild

and severe water deficit treatments was 14 and 32% less

than that in the control, respectively. However, root FW and

DW were significantly decreased by water deficit. Compared

with the control, root DW was decreased by 24 and 35% for

mild and severe water deficit treatments, respectively. Fur-

thermore, mild and severe water deficit treatments reduced

total plant DW by 23 and 37%, respectively. To account for

the effects of water deficit treatments on ginseng root

growth, root growth parameters were measured immediately

before transplanting (beginning) and after harvesting (at the

end of the water deficit experiment) (Table 2). Total root

length in the control increased by only 45% over its original

length, whereas the mild and severe water deficit treated

ginseng root length increased by 55 and 67% over their

Jinwook Lee and Kenneth W. Mudge478

Table 1. Plant growth characteristics of 4-year-old American ginseng as affected by water deficit.

Table 2. Changes in root growth parameters of 4-year-old American ginseng as affected by water deficit before transplanting and after

harvesting.

original length, respectively. On the other hand, the increase

in root diameter and root FW was significantly lower in the

mild and severe water deficit treatments than in the control.

American ginseng plants were well watered for the first

45 days immediately after transplanting followed by irrigation

intervals of 4, 10 and 20 days for the control, mild, and severe

water deficit treatments, respectively. Soil water potential

( Soil) remained at approximately 0.4 MPa in the well watered

control (4 days irrigation interval) throughout the 20 days

period shown in Fig. 1B. For the first 10 days, Soil for both

the mild (10 days irrigation interval) and severe (20 days

irrigation interval) water deficit treatments declined to

approximately 1.4 MPa. After rewatering at 10 day, Soil of

the mild water deficit treatment recovered to the same level

as the control, while that of the severe water deficit treatment

continued to decline for the next 10 days to approximately

3.6 MPa. To assess leaf moisture status, predawn leaf water

potential ( Leaf) was measured using a pressure bomb from

day 20 through day 40 after initiation of water deficit. From

an initial Leaf of approximately 0.15 MPa, the well watered

control irrigated on a 4 days interval remained at about that

level (Fig. 1A). The Leaf of the mildly water deficit treated

plants irrigated on a 10 days interval decreased to approxi-

mately 0.3 MPa after 10 days, but recovered nearly to the

level of the control after rewatering, and declined similarly

over the next 10 days. The Leaf of the severely water deficit

treated plants declined continuously during the next 20 days

without irrigation to approximately 0.5 MPa.

Daily evapotranspiration was not different for the first 4

days, but as water deficit progressed, three distinctive response

patterns were appeared depending on the corresponding

irrigation intervals (Fig. 2A). Daily evapotranspiration in well

watered control treatment was fluctuated daily. In mild water

deficit treatment, daily evapotranspiration gradually declined

during the first 6 days, but significantly decreased after the

6th day. In severe water deficit treatment, daily evapotran-

spiration showed the same trend as mild water deficit

treatment from day 0 through day 10 of the water deficit

experiment, but 10 days after irrigation, daily evapotran-

spiration rate in severe water deficit treatment remained

lower than 10 g·d-1

. Cumulative evapotranspiration did not

differ among water deficit treatments from day 0 through

day 10 of the water deficit experiment (Fig. 2B). After day

10, the increase rate of cumulative evapotranspiration for

the severe water deficit treatment declined considerably

while that of the control and mild water deficit treatments

continued to increase.

To evaluate the photosynthetic activity of water deficit

treated American ginseng leaves, stomatal conductance (gS)

Hort. Environ. Biotechnol. 54(6):475-483. 2013. 479

A

B

Fig. 1. Leaf water potential ( Leaf, A) of American ginseng and soil

water potential ( Soil, B) in response to water deficit treatments

by irrigating every 4 (control), 10 (mild stress), and 20 (severe

stress) days. Measurements were taken from day 20 through

day 40 of the water deficit experiment corresponding to the 6th

to 10th dry down cycle for the control, 3rd to 4th dry down cycle

for the mild water deficit treatment, and 2nd dry down cycle for

the severe water deficit treatment. Vertical bars represent

standard errors of the means (n = 5 and 24, for Leaf, and Soil,

respectively). Error bars representing standard errors are shown

only if greater than the size of the data point symbol itself.

A

B

Fig. 2. Daily (A) and cumulative (B) evapotranspiration of American

ginseng in response to water deficit treatments by irrigating every

4 (control), 10 (mild stress), and 20 (severe stress) day interval.

Measurements were taken from day 20 through day 40 of the

water deficit experiment corresponding to the 6th to10th dry down

cycle for the control, 3rd to 4th dry down cycle for the mild water

deficit treatment, and 2nd dry down cycle for the severe water

deficit treatment, respectively. Vertical bars represent standard

errors of the means (n = 24). Error bars representing standard

errors are shown only if greater than the size of the data point

symbol itself. Nonlinear regression equations for cumulative

evapotranspiration (B) are y = 6.8869 + 35.4486x - 0.3098x2

(r2

= 0.9983, P < 0.0001) for the control (solid line), y = 15.7465

+ 32.0542x - 0.2789x2 (r

2= 0.9945, P < 0.0001) for the mild

water deficit treatment (short dash line), and y = -10.7949 +

53.2929x - 2.6419x2 + 0.0473x

3 (r

2= 0.9977, P < 0.0001) for

the severe water deficit treatment (dotted line).

and CO2 assimilation were measured at the end of water

deficit experiment. The gS and CO2 assimilation decreased

as water deficit progressed (Table 3). In severe water deficit

treatment, gS and CO2 assimilation was 5.6- and 3.1-fold

lower as compared with those of controlled plants, respect-

ively. In addition, leaf chlorophyll b and total chlorophyll

content (Chl a + b), which influence photosynthetic rate,

were significantly reduced by water deficit treatments, but

chlorophyll a content was not statistically different (Table

3). The ABA concentration increased with the progression

of water deficit (Table 3), and ABA response was inversely

responded to stomatal conductance and CO2 assimilation.

Individual ginsenosides Re, Rb1, Rc, and Rd, and total

ginsenoside contents increased with the progression of water

deficit (Table 4). However, individual ginsenosides Rg1 and

Rb2 were not affected by water deficit treatments. In addition,

individual ginsenosides Re and Rb1 made up more than

60% of total ginsenoside content. The content of total

ginsenosides, which are sum of six individual ginsenosides,

was increased in the severely water deficit treatment (1.9%)

as compared with the control (1.6%). Furthermore, individual

ginsenosides Rb1, Rc, and Rb2 were statistically influenced

by the covariate, the rootlet fresh weight before transplanting

(RFWBT). However, total ginsenoside was not affected by

the RFWBT, covariate, but only by water deficit treatments.

There was no statistical interaction effect on water deficit

Jinwook Lee and Kenneth W. Mudge480

Table 3. Stomatal conductance (gs), CO2 assimilation, contents of chlorophyll a, b and a + b, and ABA concentration of 4-year-old

American ginseng leaves as affected by water deficit.

Table 4. Contents of individual ginsenoside and total ginsenoside of 4-year-old American ginseng roots as affected by water deficit.

treatment and the covariate (RFWBT).

Discussion

Water deficit, one of the major abiotic stresses, can con-

tribute to changing the fundamental metabolism of higher

plants to cope with adverse environment. In a higher plant,

the secondary metabolism is up-regulated by water deficit

rather than the primary metabolism for the plant growth and

development, and/or maintenance. Therefore, the reduction

of plant growth and development, and horticultural and

agricultural crops yield caused by water deficit has been

well documented. Water deficit effects on American ginseng

have not previously been studied in detail. However, Lim et

al. (2006) reported that the moderate water stress did not

affect ginseng growth, but affected the compositions and

contents of certain individual root ginsenosides. In the

present study, a significant reduction of root growth in

response to reduced soil moisture was observed (Tables 1

and 2). This finding is partially consistent with that of Mork

et al. (1981) and Li and Berard (1998), who reported that

root growth and yield decreased with soil moisture levels in

Asian and American ginsengs, respectively. On the other

hand, they also presented that shoot growth was suppressed

by soil moisture content. In this study, however, shoot

growth in terms of shoot FW and DW was not significantly

affected by water deficit treatments, although leaf area was

statistically reduced (Table 1). This response can be explained

by the determinant growth and development pattern of

American ginseng plants, since the shoot is fully developed

and enlarged to full height and leaf size within several

weeks after emergence (Lim et al., 2006; Proctor and Bailey,

1987). In the present study and that of Lim et al. (2006),

water deficit treatment had no effect on shoot growth

because water deficit treatments were not imposed until 45

and 28 days after transplanting, respectively, after shoot

growth was completed. In addition, while shoot biomass

was not significantly affected by the elevated temperatures,

root biomass in three-year-old American ginseng plants

cultivated in a greenhouse was strongly reduced (Jochum et

al., 2007). On the other hand, Lee et al. (1982) and Li and

Berard (1998) imposed water deficit treatment immediately

after transplanting, before the completion of shoot emergence

and shoot elongation. Since root enlargement occurs after

the completion of shoot enlargement, until the end of the

growing season, it is reasonable that the water deficit

Hort. Environ. Biotechnol. 54(6):475-483. 2013. 481

treatment in this experiment should inhibit root growth but

not shoot growth. Therefore, during the stage of full devel-

opment and enlargement of shoot system after shoot emer-

gence, irrigation management for preventing water deficit

should play a significant role in the further growth and

development of ginseng storage root system for the better

quality and higher root yield. In addition, ginseng root

diameter and FW decreased with progressive water deficit,

while total root length, representing the sum of the storage

root length and the longest fibrous root length, increased

with increasing water deficit (Table 2). This result is in an

agreement with the results of Lee et al. (1982) and Li and

Berard (1998). Increased root elongation, rather than diameter

or fresh weight, in response to drought stress suggests that

more assimilates are directed toward root elongation, facilitating

uptake of soil moisture.

In the case of the severe water deficit treatment in this

study (20 days irrigation interval), the rate of increase of

cumulative evapotranspiration declined dramatically. The

transpiration of cassava under progressive water deficit was

dramatically reduced at the 3rd day after imposing water

deficit (Alves and Setter, 2000). With the decline of evap-

otranspiration, Leaf under severe water deficit treatment

gradually declined (Fig. 1A). The Leaf was approximately

0.3 MPa more negative under severe water deficit treatment

than in the control. This result is similar to the Leaf in

cassava affected by water stress (El-Sharkawy et al., 1992).

However, Leaf in the present study was significantly greater

(less negative) than that of previous study with American

ginseng (Lim et al., 2006). The longer water deficit progressed,

the more Leaf decreased. This is consistent with the behavior

of cassava as reported by El-Sharkawy et al. (1992).

The reduction of available internal moisture (decreased

Leaf) within ginseng plant in this study is consistent with

declining stomata conductance, CO2 assimilation and chloro-

phyll content (Table 3), and increasing ABA levels (Table

3), consequently resulting in decreased root fresh weight

and diameter (Table 1). This result is consistent with the

finding of Lee et al. (1982) that net photosynthesis rates in

Asian ginseng decreased with soil water content. The photo-

synthetic activity and stomatal conductance of sweet potato,

which has a storage root system like ginseng, was similarly

reduced in response to water deficit (Haimeirong and Kubota,

2003). Photosynthesis and stomatal conductance in sweet

potato were substantially greater than those in ginseng leaves,

but this is not unexpected since ginseng plants are well

adapted to low light environments under the dense shaded

canopy of a deciduous hardwood forest (Proctor and Bailey,

1987). As in soybean (Inamullah and Isoda, 2005), chlorophyll

content in this study was significantly decreased in response

to water deficit, indicating that the observed decline in CO2

assimilation might be related to the degradation of chlorophyll.

Furthermore, the elevated temperatures reduced light-saturated

net photosynthetic rates and stomatal conductance in three-

year-old American ginseng plants grown in a greenhouse

(Jochum et al., 2007). Total chlorophyll content was signifi-

cantly reduced by water deficit treatment as compared with

control. Although chlorophyll a was not statistically different

between the control and water deficit treatments, water

deficit treatment tended to reduce the level of chlorophyll a.

Thus, the reduction of total chlorophyll content was not only

come from the decline of chlorophyll b content, but also

partially derived from the decrease in chlorophyll a content.

Typically, water stress contributes to the reduction of total

chlorophyll, and chlorophyll a and b contents (Zhang et al.,

2011). It is understood that less contribution of chlorophyll

a content on total chlorophyll content might be originated

from physiological and ecological characteristics of American

ginseng as a shade loving plant (Proctor and Bailey, 1987).

Water deficit treatment likely reduced the chlorophyll a

content, but the statistical difference was not appeared. This

response might be resulted from the huge variation of

chlorophyll a content to water deficit in the individual plants.

Although the increase of ABA level in response to water

deficit has been well documented in many horticultural

crops (Alves and Setter, 2000; Bauerle et al., 2004, 2006;

Setter et al., 2001; Wang et al., 2004), ABA levels have not

been reported for American ginseng leaves. In this present

work, foliar ABA levels were 3.5 times higher than the

control by the end of severe water deficit (Table 3). The

increase in foliar ABA induced by water deficit has been

shown to reduce leaf area (Trejo et al., 1995; Zhang and

Davies, 1990) as reported in this study. In cassava which

has a storage root system similar to ginseng, a 5- to 7-fold

increase in ABA concentration was reported (Alves and

Setter, 2000). Although the pattern of ABA accumulation in

cassava and ginseng was similar, the absolute concentration

of foliar ABA was substantially higher in cassava.

Up-regulation of ginsenosides reported by Lim et al.

(2006) and this study appeared to be consistent with other

reports of up-regulation of secondary metabolites in response

to abiotic environmental stress as has been reported by

Bouchereau et al. (1996), Kirakosyan et al. (2003) and Liu

(2000). Environmental effects on the composition and accu-

mulation of root ginsenosides have been reported in numerous

papers (Fournier et al., 2003; Konsler et al., 1990; Li and

Mazza, 1999). Gypsum incorporation enhanced the contents

of individual and total ginsenosides with the increase in

gypsum level while plant growth decreased (Lee and Mudge,

2013). In addition, Lim et al. (2005) reported that the com-

position and contents of root ginsenosides are significantly

affected not only by environment (garden location) but also

by genotype (population). Jochum et al. (2007) reported that

during the growing season, the elevated temperatures con-

Jinwook Lee and Kenneth W. Mudge482

tributed to increasing concentrations of root ginsenosides

Rb1, Rc, and Re. Furthermore, in this study, water deficit

treatment enhanced the level of root ginsenosides Re, Rb1,

Rc, and Rd. Therefore, abiotic environmental stresses such

as elevated temperature and water deficit could affect not

only plant growth and development but also the response of

ginsenosides. On the other hand, the level of root ginsenoside

Rg1 and Rb2 was neither affected by water deficit treatment

nor by the elevated temperature (Jochum et al, 2007). It is

considered that these root ginsenosides as minor ginsenosides

might be relatively less influenced by abiotic environmental

perturbations.

In conclusion, severe water deficit reduced root growth

(fresh weight and diameter), but up-regulated certain individual

and total ginsenosides. Water deficit also induced decreased

Leaf, increased foliar ABA concentration, and finally reduced

CO2 assimilation rate. Consequently, American ginseng root

growth and yield were significantly reduced by water deficit.

The results of this study contribute to understanding the

physiological responses of American ginseng to water deficit

and its impact on ginsenoside accumulation. From the growers

stand point of maximizing root growth, a suitable irrigation

management program may apply to intensive ginseng production

system for the better quality and higher ginseng root pro-

duction. Commercially, use of irrigation may be justified

since the growers income from the sale of ginseng is based

on root weight, but this may be achieved at the expense of

ginsenoside content.

Acknowledgements: The authors thank Joe Lardner and

Dr. Wansang Lim (Department of Horticulture, Cornell

University) for their helpful assistance and Dr. Tim L. Setter

(Department of Crop and Soil Sciences, Cornell University)

for his technical assistance of the ABA measurement. Jinwook

Lee was supported by a graduate research assistantship in

the Department of Horticulture, Cornell University.

Literature Cited

Alves, A.A.C. and T.L. Setter. 2000. Response of cassava to water

deficit; leaf area growth and abscisic acid. Crop Sci. 40:131-137.

Arnon, D.I. 1949. Copper enzymes in isolated chloroplasts. Poly-

phenoloxidase in Beta vulgaris. Plant Physiol. 24:1-15.

Assinewe, V., B.R. Baum, D. Gagnon, and J.T. Arnason. 2003.

Phytochemistry of wild populations of Panax quinquefolius L.

(North American ginseng). J. Agric. Food Chem. 51:4549-4553.

Attele, A.S., J.A. Wua, and C. S. Yuan. 1999. Ginseng pharmacology:

Multiple constituents and multiple actions. Biochem. Pharmacol.

58:1685-1693.

Barbara, K., K. Ewa, K. Jerzy, and C. Aleksander. 2006. The effect

of growth regulators on quality parameters and ginsenosides

accumulation in Panax quinquefolium L. roots. Plant Growth

Regulat. 48:13-19.

Bauerle, W.L., W.W. Inman, and J.B. Dudley. 2006. Leaf abscisic

acid accumulation in response to substrate water content: Linking

leaf gas exchange regulation with leaf abscisic acid concentration.

J. Amer. Soc. Hort. Sci. 131:295-301.

Bauerle, W.L., T.H. Whitlow, T.L. Setter, and F.M. Vermeylen. 2004.

Abscisic acid synthesis in Acer rubrum L. leaves - A vapor-

pressure-deficit-mediated response. J. Amer. Soc. Hort. Sci.

129:182-187.

Beyfuss, R.L. 1999. American ginseng production in woodlots.

Agroforest. Notes 14:1-4.

Bouchereau, A., N. Clossais-Besnard, A. Bensaoud, L. Leport, and

M. Renard. 1996. Water stress effects on rapeseed quality. Eur.

J. Agron. 5:19-30.

Clemente, H.S. and T.E. Marler. 1996. Drought stress influences

gas-exchange responses of papaya leaves to rapid changes in

irradiance. J. Amer. Soc. Hort. Sci. 121:292-295.

Delfine, S., R. Tognetti, F. Loreto, and A. Alvino. 2002. Physiological

and growth responses to water stress in field-grown bell pepper

(Capsicum annuum L.). J. Hort. Sci. Biotechnol. 77:697-704.

El-Sharkawy, M.A., A.H. Del Pilar, and C. Hershey. 1992. Yield

stability of cassava during prolonged mid-season water stress. Exp.

Agric. 28:165-174.

Ennahli, S. and H.J. Earl. 2005. Physiological limitations to photo-

synthetic carbon assimilation in cotton under water stress. Crop

Sci. 45:2374-2382.

Fournier, A.R., J.T.A. Proctor, L. Gauthier, S. Khanizadeh, A. Belanger,

A. Gosselin, and M. Dorais. 2003. Understory light and root

ginsenosides in forest-grown Panax quinquefolius. Phytochemistry

63:777-782.

Jochum, G.M., K.W. Mudge, and R.B. Thomas. 2007. Elevated tem-

peratures increase leaf senescence and root secondary metabolite

concentrations in the understory herb Panax quinquefolius (Araliaceae).

Amer. J. Bot. 94:819-826.

Kirakosyan, A., E. Seymour, P.B. Kaufman, S. Warber, S. Bolling,

and S.C. Chang. 2003. Antioxidant capacity of polyphenolic extracts

from leaves of Crataegus laevigata and Crataegus monogyna

(Hawthorn) subjected to drought and cold stress. J. Agric. Food Chem.

51:3973-3976.

Konsler, T.R., S.W. Zito, J.E. Shelton, and E.J. Staba. 1990. Lime

and phosphorus effects on American ginseng. II. Root and leaf

ginsenoside content and their relationship. J. Amer. Soc. Hort. Sci.

115:575-580.

Lee, J. and K.W. Mudge. 2013. Gypsum effects on plant growth,

nutrients, ginsenosides, and their relationship in American ginseng.

Hort. Environ. Biotechnol. 54:228-235.

Lee, S.S., D.C. Yang, and Y.T. Kim. 1982. Effects of soil water

regimes on photosynthesis, growth and development of ginseng

plant (Panax ginseng C.A. Meyer). Kor. J. Crop Sci. 27:175-181.

Li, T.S.C. 1995. Asian and American ginseng - A review. Hort-

Technology 5:27-34.

Li, T.S.C. and R.G. Berard. 1998. Effects of soil moisture on the

growth of American ginseng (Panax quinquefolium L.). J. Ginseng

Res. 22:122-125.

Li, T.S.C. and G. Mazza. 1999. Correlations between leaf and soil

mineral concentrations and ginsenoside contents in American

ginseng. HortScience 34:85-87.

Lim, W., K.W. Mudge, and J.W. Lee. 2006. Effect of water stress

on ginsenoside production and growth of American ginseng.

HortTechnology 16:517-522.

Lim, W., K.W. Mudge, and F. Vermeylen. 2005. Effects of population,

age, and cultivation methods on ginsenoside content of American

ginseng (Panax quinquefolium). J. Agric. Food Chem. 53:8498-8505.

Liu, Z. 2000. Drought-induced in vivo synthesis of camptothecin in

Camptotheca acuminata seedlings. Physiol. Plant. 110:483-488.

Mork, S.K., S.Y. Son, and H. Park. 1981. Root and top growth of

Panax ginseng at various soil moisture regime. Kor. J. Crop Sci.

26:115-120.

Hort. Environ. Biotechnol. 54(6):475-483. 2013. 483

Proctor, J.T.A. and W.G. Bailey. 1987. Ginseng: Industry, botany,

and culture. Hort. Rev. 9:187-236.

Reaves, M.E., 2003. Gas exchange and water relations of red maple

Acer rubrum L. ecotypes and cultivars in response to drought.

Cornell University, Ithaca, NY.

Setter, T.L., B.A. Flannigan, and J. Melkonian. 2001. Loss of kernel

set due to water deficit and shade in maize: Carbohydrate supplies,

abscisic acid, and cytokinins. Crop Sci. 41:1530-1540.

Trejo, C.L., A.L. Clephan, and W.J. Davies. 1995. How do stomata

read abscisic acid signals? Plant Physiol. 109:803-811.

Wang, Z., B. Huang, S.A. Bonos, and W.A. Meyer. 2004. Abscisic

acid accumulation in relation to drought tolerance in Kentucky

bluegrass. HortScience 39:1133-1137.

Zhang, J. and W.J. Davies. 1990. Changes in the concentration of

ABA in xylem sap as a function of changing soil water status

can account for changes in leaf conductance and growth. Plant

Cell Environ. 13:277-285.

Zhang, Y.J., Z.K. Xie, Y.J. Wang, P.X. Su, L.P. An, and H. Gao.

2011. Effect of water stress on leaf photosynthesis, chlorophyll content,

and growth of oriental lily. Russian J. Plant Physiol. 58:844-850.