INTRODUCTION
Among various problems faced by crop plants, water

stress is considered to be the most critical one (Boyer, 1982).
Since plants being immobile, cannot evade water stress in
the same way as other mobile organisms. Therefore, plants
adopt many morphological and physiological alterations to
acclimatize to stressful environment (Sakamoto and Murata
2002). One such mechanism that is ubiquitous in plants is
the accumulation of organic metabolites collectively called
as compatible solutes (Bohnert et al, 1995). These
compatible solutes act as an osmoprotectant (Burnett et al,
1995). Among the osmoprotectant, glycinebetaine
considered to be one of the most predominant and most
effective osmoprotectant (Burnett et al, 1995). However,
not all plants can produce osmolytes in sufficient quantities
to combat drought. In many crops genotypic engineering
was adopted to increase or initiate the synthesis of
glycinebetaine. However, biosynthesis of glycinebetaine
through genetic engineering is costly (Hanson and Wyse,
1982) and most of the plants do not normally accumulate
sufficient amount of osmolytes. The exogenous application

Influence of exogenous glycinebetaine on hot pepper under water stress

R.M. Bhatt, N.K. Srinivasa Rao and A.D.D.V.S. Nageswara Rao
Division of Plant Physiology and Biochemistry
ICAR-Indian Institute of Horticultural Research

Hesaraghatta Lake Post, Bengaluru - 560 089, India
E-mail: rmbt@iihr.ernet.in

ABSTRACT
A study was conducted to evaluate the effect of exogenous application of glycinebetaine (GB) on physiological

response in hot-pepper (Capsicum annuum L. vs. Arka Lohit and Pusa Jwala) under water stress. Glycinebetaine was
applied to seeds as well as plants through foliar applications. Water stress affected considerably the morpho-
physiological parameters in both the cultivars. However, in glycinebetaine (GB) treated plants, plant height, leaf area
(LA), flower and fruit number and total dry matter (TDM) were greater compared to the untreated stress plants (T4)
under water stress. Glycinebetaine application enhanced the photosynthesis (PN) in water deficit experiencing plants,
mostly due to a greater stomatal conductance (gs) and carboxylation efficiency of CO2 assimilation. In both the
cultivars after 12 day of stress, the PN decreased from 10.1 to 1.0-1.3 μ mol m

-2 s-1 in untreated stressed plants (T4),
while in the treated stressed plants PN had reduced to 2.0 – 3.0 μ mol m

-2 s-1 (T1 – T3). The application of GB increased
the WUE in both the cultivars. The better WUE in treated plants of hot-pepper under stress was attributed to the
improved PN. The higher per plant yield in the GB applied plants under stress in both the cultivars associated with
higher PN rate, gs and WUE in treated plants. Though there was an increase in PN rate, WUE and plant yield in the
treated plants (T1 – T3), the better results were found in the plants (T2) where seeds were treated and foliar application
was given at the time of imposing stress.

Key words: Glycinebetaine, hot pepper, photosynthesis, stomatal conductance

of glycinebetaine has been suggested as an alternative
approach to improve tolerance under water stress (Makela
et al, 1996). Application of glycinebetaine has been shown
to protect functional protein, vital enzymes and
photosynthetic machinery (Xing and Rajashekar, 1999) and
has been found to improve the crop water productivity under
limited and well watered conditions (Hussain et al, 2008).

However, such studies are lacking in the horticultural
crops like hot-pepper, though it is being grown under tropical
and sub-tropical conditions. Therefore, the present study
was conducted to evaluate the effect of exogenous
application of glycinebetaine on physiological response in
hot-pepper under water stress.

MATERIAL AND METHODS
Plant material and glycinebetaine treatment: The
seedlings of hot-pepper genotypes, Arka Lohit and Pusa
Jwala were raised in seedling trays containing coco peat.
One month old seedlings were transplanted in the plastic
pots (12’’dia.) containing sandy soil and farmyard manure
(3:1 v/v) under natural environmental conditions. The day

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Vol. 9(2):153-156, 2014

154

temperature varied from 34 to 36oC and photosynthetic
photon flux density (PPFD) from 1000 to 1900 µ mol
m-2s-1 during the study. The plants were irrigated regularly
and the recommended package of practices was followed
to grow the plants. Water stress was imposed at flowering
stage (35 days after transplanting) by withholding irrigation
for a period of 12 days. The GB treatment was given to
seed (6.0%) before sowing and plants through foliar spray
(1.0%) at the time of imposing water deficit stress. The
treatments were defined as follows: T1 = water deficit stress
+ seeds treatment with 6% GB, T2 = water deficit stress +
seeds treatment with 6% GB + foliar spray (1.0%), T3 =
water deficit stress + foliar spray only, T4 = water deficit
stress, T5 = irrigated plants. Soil moisture content as
measured gravimetrically was 20-22% in the control and
11-13% under the stress.

Morpho-physiological observations: Gas exchange
parameters such as net photosynthesis rate (PN), stomatal
conductance (gs) and internal CO2 (Ci) were measured using
portable Photosynthesis Analysis System (Model LCA 3,
Analytical Development Corporation, Huddesdon, U.K).
Fully expanded leaf (5th leaf) from top was used clamped
to the leaf chamber and the observations were recorded
when PN, gs and Ci were reached to stable value under
natural conditions. All the gas exchange parameters were
recorded between 10.00 and 11.30h. The osmotic potential
(ψs) was measured using Wescor osmometer (model 5520).
The observations were also recorded on plant height, leaf
area, number of flowers and fruits. Leaf area was measured
by leaf area meter (LI-3000). Plant samples were collected
at the time of releasing the stress and dried in oven at 80oC
for 48h to determine the total dry matter (TDM). The plant
fruit yield was measured on fresh weight basis.

RESULTS AND DISCUSSION
The effect of GB on plant height, leaf area, flower

and fruit number and total dry matter (TDM) were shown
in Table 1. There was considerable effect of GB treatments
on these parameters under water stress. The TDM
accumulation was 8.7 to 11.5% in Arka Lohit and 3.0 to
36.7% higher in Pusa Jwala in treated plant (T1–T3) as
compared to untreated plants (T4) under stress (Table 1).
In both the cultivars, the response was better to GB
treatments applied to both seeds + foliar treatment (T2). A
significant decrease in PN and gs was found by 12 days
after stress in both the cultivars (Fig. 1a and 1b). Reduction
in PN was sharp in Pusa Jwala as compared to Arka Lohit.
At the end of 12 days stress, PN decreased from 10.1 to
1.0-1.3 µ mol m-2 s-1 in untreated stressed plants (T4), while

Table 1. Morpho-physiological parameters as affected by
glycinebetaine application under stress in two cultivars of hot
pepper
Variety Treatment Plant Leaf Flower Fruit Total dry

height area No. No. matter
(cm) (cm2) (g plant-1)

Arka Lohit T1 76.0 659.2 50 8 22.629
T2 84.0 1094.0 53 7 23.223
T3 92.0 1374.0 65 7 22.635
T4 75.0 720.6 50 6 20.810
T5 80.0 2615.2 70 20 46.394
SEM 1.38 158.86 2.40 1.17 2.16

Pusa Jwala T1 62.0 1017.0 25 8 16.589
T2 68.0 1328.6 50 8 20.291
T3 56.0 1145.0 58 5 15.309
T4 50.0 778.0 41 8 14.84
T5 70.0 2049.0 53 21 34.236
SEM 1.66 96.53 2.59 1.26 1.62

T1 = water deficit stress + seeds treatment with 6% GB, T2 = water
deficit stress + seeds treatment with 6% GB + foliar spray (1.0%),
T3 = water deficit stress + foliar spray only, T4 = water deficit stress
and T5 = irrigated plants

in GB treated stressed plants PN reduced to 2.0 – 3.0 µ mol
m-2 s-1 (T1 – T3). Similarly, gs reduced from 0.84 mol m-2
s-1 to 0.04 mol m-2 s-1 in untreated stress plants, while in
treated stress plants, it was 0.89 to 0.06 mol m-2 s-1. Among
the treated plants, the higher gs (0.08 to 0.10 mol m

-2 s-1)
was found in T2 in both the cultivars. The recovery in PN
and gs after releasing 12 days stress was almost the same
in both the cultivars (Fig. 1a and 1b). The Ci value was
higher in untreated stress plants (T4) as compared to the
plants treated with GB (T1 – T3) in both the cultivars (Table
2). Similar trend was observed for A/Ci ratio. The WUE
reduced in both the cultivars under stress in untreated plants
(0.26 – 0.38 µ mol CO2/ mol H2O m

-2s-1). However, the
decrease in WUE was less in the plants treated with GB
and ranged from 0.53 to 0.70 µ mol CO2/ mol H2O m

-2s-1 in
Arka Lohit and 0.30 to 0.47 µ mol CO2/ mol H2O m

-2s-1 in
Pusa Jwala. The ψs in the irrigated plants varied from -1.10
to -1.16 MPa. Under stress, it decreased up to -2.0 to -2.32
MPa under stress (T4) in both the cultivars. GB treated
plants (T1 – T3) of Arka Lohit had the ψs of -2.45 to -3.00
MPa and Pusa Jwala -2.59 to -2.90 MPa (Table 2). The
per plant yield was 267 – 294g plant-1 in Arka Lohit and 204
– 213 g plant-1 in Pusa Jwala in the treated stress plants
(T1 – T3), while in untreated stress plants (T4) it was 252
g plant-1 in Arka Lohit and 156g plant-1 in Pusa Jwala (Fig.
2). The effect of GB on plant response to water stress was
better in T2.

Our studies confirmed that the application of GB
improved the LA production, plant height and TDM

Bhatt et al

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Vol. 9(2):153-156, 2014

155

Fig.1a. Pattern of photosynthesis and stomatal conductance as
affected by glycinebetaine application during water stress in hot
pepper var. Arka Lohit

accumulation and PN rate under water deficit. Generally,
the reduction in PN under water-deficit is caused by either
stomatal closure and/or photosynthetic apparatus damage.
Stomatal closure has an effect on CO2 entering cells,
whereas continuous moderate or sever absence of water
can damage the photosynthetic apparatus (Makela et al,
1999). Our study indicated that water deficit considerably
reduced the PN and gs in hot pepper. The GB application
alleviated these disturbances caused by water deficit in both
the cultivars (Fig. 1a and Fig. 1b). There was an increase
in Ci under stress condition (T4). An increase in Ci with a
decrease in PN and gs in untreated plants under stress (T4)
suggests a decline in biochemical capacity of the plants.
The greater A/Ci ratio in the GB applied plants indicates
the improvement in carboxylation efficiency in the GB applied
plants under water stress. The application of GB improved

gs and protected the photosynthetic apparatus, which resulted
in the higher PN under water deficit and alleviation of
negative effects (Fig. 1a & b and Table 2). Ma et al, (2007)
also found that in tobacco the foliar application of GB
improved the PN under water stress mostly due to a greater
gs and carboxylation efficiency of CO2 assimilation. The
GB application also resulted in a decrease in ψs in both the
cultivars (Table 2). Glycinebetaine is thought to act as a
compatible solute; therefore, its accumulation decreases ψs
and improves the leaf water status in these cultivars. The
decrease in ψs may improve the leaf water status. Earlier
studies also shown the application of GB improved water
status of plants under stress (Xing and Rajashekar, 1999).
Further, the application of GB increases the WUE in both
the cultivars. Makhdum and Shabad-ud-Din (2007) found
an increase in WUE in GB applied plants of cotton under

Fig. 1b. Pattern of photosynthesis and stomatal conductance as
affected by glycinebetaine application during water stress in hot
pepper var. Pusa Jwala

Influence of exogenous glycinebetaine on hot pepper under water stress

J. Hortl. Sci.
Vol. 9(2):153-156, 2014

156

water stress. The better WUE in treated plants of hot-pepper
under stress was attributed to the improved PN. The higher
per plant yield in the GB applied plants under stress in both
the cultivars of hot-pepper attributed to higher PN rate, gs
and WUE in treated plants. Among the treatments, best
results were found in T2, where GB treatment was given to
seeds and foliar application.

Table 2. Net photosynthetic rate (PN, μmol m
-2s-1), stomatal

conductance (gs, mol m-2s-1), intercellular carbon dioxide (Ci, ppm),
water use efficiency (WUE, μmol CO2/ mol H2O m

-2 s-1) and leaf
osmotic potential (ψψψψψs,-MPa) as influenced by glycinebetaine
application under stress in hot pepper
Variety Treatment A Gs Ci A/Ci WUE ψ s ,
Arka Lohit T1 1.6 0.06 337 0.005 0.59 2.45

T2 3.0 0.10 306 0.010 0.70 3.00
T3 2.0 0.07 303 0.007 0.53 2.50
T4 1.0 0.05 351 0.003 0.26 2.00
T5 12.1 0.67 289 0.042 1.11 1.16
SEM 0.92 0.05 5.15 0.003 0.06 0.14

Pusa Jwala T1 1.5 0.06 314 0.004 0.30 2.59
T2 2.5 0.08 300 0.008 0.47 2.90
T3 2.0 0.07 333 0.006 0.40 2.60
T4 0.8 0.04 331 0.002 0.38 2.32
T5 11.2 0.50 304 0.037 0.98 1.10
SEM 0.86 0.04 3.03 0.003 0.05 0.14

T1 = water deficit stress + seeds treatment with 6% GB, T2 = water
deficit tress + seeds treatment with 6% GB + foliar spray (1.0%),
T3 = water deficit stress + foliar spray only, T4 = water deficit stress
and T5 = irrigated plants

Fig. 2. Effect of glycinebetaine on plant yield under water stress
in two cultivars of hot pepper

ACKNOWLEDGEMENT
The authors are thankful to the Director, ICAR-IIHR,

Bengaluru for providing necessary facilities and to Mr. C.
Muniraju for technical help.

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Bhatt et al

(MS Received 26 November 2013, Revised 22 July 2014, Accepted 30 July 2014)

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Vol. 9(2):153-156, 2014