Journal
Journal of Applied Horticulture, 19(3): 245-248, 2017
Appl
The role of salt (NaCl) stress on seed germination, growth and
proline content of some tomato varieties
Nurul Aini, Wiwin Sumiya D.Y. and Adi Setiawan
Agriculture Faculty, University of Brawijaya, Jl. Veteran, Malang, East Java, Indonesia, 65145.
*E-mail: rully_aini@yahoo.com
Abstract
The tomato production continuously needs to be improved to fulfill the demand of food industry and medicine. The soil salinity is a
limiting factor in germination, growth and production of tomatoes. Therefore, screening was done using salt-tolerant tomato to examine
the tolerance mechanism of some tomato varieties. Six tomatoes varieties, i.e., Betavilla, Permata, Servo, Tymoty, Mutia, and Patma
were tested using various NaCl concentrations in the growth medium. The germination and growth rate of the varieties on a range
of salt conditions were examined to find varieties that were resistant to salt. This study showed that Permata, Servo, and Mutia are
more tolerant to the salt when compared with Betavilla, Tymoty, and Patma. Moreover, salt-sensitive varieties accumulated proline in
leaf higher than saline-tolerance one. The condition suggested that mechanism of salt-tolerance in the varieties is other than proline
accumulation. Further study is require to understand the salt-tolerant mechanism in tomatoes.
Key word: Salt stress, NaCl, tomato varieties, chlorophyll, proline, Na+/K+Leaves
Introduction
Tomato (Lycopersicum esculentum L.) is a valuable commodity
as source material for the processed food industry and medicine.
Tomato is rich in nutrients such as vitamins, mineral, and
antioxidants. The expansion of planting area into the peripheral
area including saline land can be an alternative for increasing
tomato production. Approximately 800 million hectares of land
are affected by high salt concentrations throughout the world
(Munns, 2002). However, a high level of salinity frequently
encountered severe constraints to growth of tomato. Salinity
can affect germination and seedling growth either by creating an
osmotic pressure that prevents water uptake or by the toxic effects
of sodium and chloride ions (Hopper et al., 1979). Therefore,
cultivation of tomato on saline land requires a profound
understanding of the variation and physiological characters and
their mechanisms.
Salt stress can reduce productivity and chlorophyll content of
chickpeas leaves (Garg and Singla, 2004) and influence the
ability of seed germination of pepper (Hassen et al., 2014). The
application of NaCl 2.4 dSm-1 may affect the leaf area of tomato
and increasing salinity level gradually until 4.8 dS-1 (NaCl)
reduces vegetative growth, yield and quality characteristics
(Siregar et al., 2013). Other report stated the application of 0-750
ppm NaCl effects on the early growth of seedlings (Siregar et
al., 2013).
The high concentration of salt is environmental stress affecting
plant productivity (Gharbi et al., 2017), which stimulates water
deficit and oxidative damage in plants (Munns, 2002; James
et al., 2011). The tolerance to salinity varies for every phase
of growth, and varieties of tomato (Aini et al., 2012; Guan et
al., 2010). Salt-tolerant plants can grow more efficiently under
saline conditions (Foolad, 2004). The study and identification of
the mechanisms of the tolerance of plants under salinity stress
conditions will be very useful for the breeder to select a tolerant
variety of plant (Alikhani et al., 2011). The aim of the research
was to understand the response of six varieties of tomato plants
to saline stress (NaCl) and to examine the mechanism of saline
tolerance.
Materials and methods
Influence of saline stress on germination rate: The effect
of saline stress on germination rate was studied in factorial
completely randomized design. Seeds of six tomato varieties
of Betavilla, Permata, Servo, Tymoty, Mutia, and Patma were
soaked in water for 3-5 hours and then soaked in warm water for
30 minutes. The seeds were sown in Petri dishes (50 seeds each
petri dish) that contained NaCl (0, 2, 4, 6, and 8 g L-1). Percentage
of germination (GP) was calculated using the formula: GP =
[(Total germinated seed/ Total number of seed) x 100] (Ashraf
and Foolad, 2005).
Influence of salt stress on growth rate: The experiment was
arranged using Split-Plot Design. The main plots were six tomato
varieties of Betavilla, Permata, servo, Tymoty, Mutia, and Patma.
Stress was created with concentrations of NaCl (0, 2, 4, 6, and
8 g L-1). Overall, there were 40 combinations of treatment, with
three repetition. Each treatment consisted of six plants so that
the total crop was 720 plants. The experiment was carried out
in the greenhouse at an altitude of 303 m above sea level with
an average temperature of 27-29°C. Two seeds of each variety
were sown in each of plastic containers (8-9 cm), then seeds were
covered with planting medium and watered to keep them moist.
Maintenance at the nursery included irrigation, pest, and disease
control under field conditions. When the tomato seedlings were
ready to be planted, they were transferred into polybags filled
with non-saline soil media as much as 6 kg. The seedlings were
treated with salt stress on 7 DAP (day after planting) by applying
a solution of NaCl as per treatment with the appropriate volume
till it reached field capacity.
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Salt stress influence on seed germination, growth, and proline content of some tomato varieties
The plants maintenance included thinning, replanting, fertilization,
irrigation, weeding and diseases control. Plants thinning was done
on 6 days after transplanting (DAT) by leaving plants that grew
well. Dead plants were replaced with new seedlings. Fertilization
was applied 7 DAT with NPK fertilizer. Irrigation used tap water
7 DAT; the later irrigation used a solution of salt (NaCl) with a
concentration according to treatment. Irrigation was continued
using tap water after maintaining the EC of the medim as per
treatment. Weeding was done manually. Pest and disease control
was done to prevent pests and diseases according to the conditions
in the field. The plant height was observed once a week while
proline content on leaves and Na+/K+leaves ratios were measured
once at eight weeks after planting using the slightly modified
method of Bates et al. (1973). The EC of the planting medium
was measured using EC meter started two weeks after planting at
intervals of once a week. Sodium/potassium ratios of the youngest
three leaves (Na/KLeaves) were determined by flame photometry
at the late vegetative stage. The data were then analyzed using
analysis of variance (ANOVA) to determine the effect of the
treatments applied. If there was a significant difference of
treatment then continued with Least Significant Differences test
of P=0.05.
Results and discussion
Influence of salt stress on germination rate: NaCl application
was proved to be successful in maintaining the media salinity
until the end of the experiment (Fig. 1A). The result showed that
saline influenced seed germination depending on the variety of
the tomato. This result is similar to previous reports (Abari et
al., 2011; Hassen et al., 2014; Kurniasih, 2013). The Permata,
Servo, and Mutia varieties had high germination percentage
that was respectively 86.67, 90 and 90.83% at the highest salt
concentration treatment (8 g L-1). Whereas, the lowest germination
percentage was shown by the variety Timoty (3.67%) (Fig. 1B).
The result indicated that varieties Permata, Servo and Mutia have
more tolerance against saline compared with others. The saline
stress may hamper absorption of water into the seed that reduces
the germination rate of the tomato.
Influence of salt stress on growth rate: Saline medium
undoubtedly influenced the growth of tomato four weeks after
plantation (Table 1). The salinity inhibited tomatoe growth
depending on the dose of NaCl. Further investigation showed
that the saline tolerant varieties of tomatoes (Permata, Servo,
and Mutia) grew better than other varieties (Table 2). The data
suggested that the high concentration of salt decreased water
potential that hampered water imbibitions into the seed and plant.
Water is essential for germination, photosynthesis, and other
metabolism in the plant. The increasing salinity will deprive
water, which will detain germination and growth. Therefore,
the saline tolerant varieties have better germination, and growth
faster than other varieties.
Table 1. Effect of salinity (NaCl) levels on plant height of tomato at
different time of observation
Treatment
Plant height (cm)
2 WAP
3 WAP
4 WAP
5 WAP
0 g NaCl l-1
21.14
50.33
62.31c
67.71c
2 g NaCl l-1
18.92
47.06
60.33bc
65.71c
4 g NaCl l-1
19.28
45.97
57.76b
61.57b
6 g NaCl l-1
19.94
44.53
56.83ab
58.90ab
8 g NaCl l-1
20.65
48.36
53.86a
56.17a
LSD (5%)
NS
NS
3.34
2.89
Different letters in each column show a significant difference at P≤0.05
(*) by Least significant difference. The non-significant difference
represented by NS. WAP =week after planting.
Germination (%)
Table 2. Plant height of different varieties of tomato at different time
of observation
Variety
Plant height (cm)
2 WAP
3 WAP
4 WAP
5 WAP
Permata
21.93c
48.53bc
60.27c
63.25c
Servo
23.80d
52.00c
62.22c
66.93cd
Mutia
21.67c
48.87bc
61.33c
64.32c
Betavilla
18.53b
46.30b
55.17ab
60.58b
Tymoty
15.43a
42.40a
53.50a
56.78a
Patma
18.55b
45.40ab
56.83b
60.20b
LSD (5%)
2.03
3.88
2.74
2.65
Different letters in each column show a significant difference at P≤0.05
(*) by Least significant difference. WAP = week after planting
Fig. 1. Changes in EC (dS m -1) with the application of different
concentrations of NaCl (A). Percentage of germination of tomato
varieties at different concentrations of NaCl. The Permata, Servo, and
Mutia varieties have tolerance to saline stress indicated by the high
percentage of germination at the highest concentration of NaCl (B).
Several reports suggested that plant synthesizes and accumulate
proline under salt stress to maintained osmotic potential (de
Lacerda et al., 2005; Koca et al., 2007; Mansour et al., 2005).
Furthermore, the analysis on the proline content in the tomatoes
under saline stress showed that the content of proline was
associated with salt concentration, the leaf proline content
increased with salinity levels (Fig. 2A). However, the proline
content is significantly correlated with salt tolerant varieties
(Fig. 2B). Proline accumulation in tolerant varieties (Permata,
Servo and Mutia) was markedly decreased compared to the
sensitive varieties (Fig. 2B). The results are similar with
Journal of Applied Horticulture (www.horticultureresearch.net)
Salt stress influence on seed germination, growth, and proline content of some tomato varieties
A
247
A
B
B
Fig. 2. Proline content of tomato leaves at different levels of NaCl.
Proline content increased with increasing NaCl level (A), and
accumulated proline content in different varieties of tomato (B).
previously reported on corn (Cha-Um and Kirdmanee, 2009). The
phenomenon indicated that salinity tolerance in tomato might be
due to other mechanisms.
The plant survival ability to saline stress could be through ion
homeostasis (Zhang et al., 2006). The ratio Na+/K+ in the tomato
leaves analysis was to determine whether application of salt stress
affects the balance of ions inside the cell. The results indicated
that Na+/K+ ratio increased with increasing salinity level over 6 g
(Fig. 3 A). Salinity levels exhibited noteworthy effect on the Na+/
K+ ratio in tomato varieties. The lowest sodium/potassium ratio
was in Mutia and the higher in Permata, Servo and Tymoty. The
data showed that K+ absorption in tomato plant was decreased
due to the excess Na in the medium. Sodium has antagonist
effect on K+ uptake by plants (Ashraf and Sarwar, 2002). This
study suggested that three tomato varieties, i.e., Permata, Servo,
and Mutia has more tolerance to the salt and may be used for
cultivating in the salty land.
Permata, Servo, and Mutia varieties are more tolerant to saline
stress compared to Betavilla, Tymoty, and Patma. The salinetolerant varieties have better germination rate and vegetative
growth. However, the saline-tolerant varieties accumulate proline
lower than saline sensitive varieties that likely to have other
mechanisms to adapt to saline conditions.
Acknowledgment
Authore thank DITJEN DIKTI for providing funds through
the Competitive Research Grant Program for Decentralization
Research with contract number: 530. 25/ UN10.21 / PG / 2015.
We sincerely thank Dr. Nashi Widodo, Biology Laboratory,
Department of Biology, University of Brawijaya.
Fig. 3. Na+/K+ of tomato leaves at different levels of NaCl. Na+/K+
increased at high level (6 and 8 g L-1) of NaCl (A), and different varieties
of tomato showed difference ratio of Na+/K+(B)
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Received: May, 2017; Revised: September, 2017; Accepted: September, 2017
Journal of Applied Horticulture (www.horticultureresearch.net)