Reserarch on Crop Ecophysiology Vol. 9/1, Issue 1 (2014), Pages:13 - 20 Original Research
Influence of
NaCl Seed Priming on Growth and Some Biochemical Attributes of Safflower Grown
under Saline Conditions Elouaer
Mohamed Aymen 1 *, Ben Fredj Meriem 1, Zhani Kaouther 1,Hannachi
Cherif 1 Sousse University, High Institute
of Agronomy, Chott Mariem, 4042, Tunisia *
Corresponding
author E-mail: aymenouaer@gmail.com Received: 17 July 2013 Accepted: 12
November 2013 Abstract This experiment was conducted to evaluate the effects of NaCl priming on
growth traits and some biochemical attributes of safflower (Carthamus
tinctorius L. cv Safola) in salinity conditions. Seeds of safflower were
primed with NaCl (5 g L-1) for 12 h in 23 °C. Primed (P) and non primed
(NP) seeds were directly sown in the field. Experiments were conducted using
various water concentrations induced by NaCl (0, 3, 6, 9 and 12 g L-1)
in salinity experiment. Results showed that growth (plant height, fresh and dry
weight) and biochemical (chlorophyll, proline and proteins content) of plants
derived from primed seeds were greater of about 15 to 30% than that of plants
derived from non primed seeds. It seems that salinity tolerance in priming
resulted plants was due to higher potential of these plants to accumulate more
biochemical attributes (more chlorophylles, proline and proteins in primed
plants than controls ones). Keywords: Biochemical attributes, Growth parameters, Safflower, Salinity, Seed
priming Introduction Salt stress is certainly one of the most serious
environmental factors limiting the productivity of crop plants (Ashraf, 1999).
This is due to the fact that salinity affects most aspects of plant physiology,
growth and development (Borsani et al., 2003). One metabolic response to
salt stress is the synthesis of compatible osmolytes (Hasegawa et al., 2000). These organic compounds are
thought to mediate osmotic adjustment, protecting cellular structures and
oxidative damage by their free radical scavenging capacity (Smirnoff, 1993). Metabolic
acclimation via the accumulation of compatible solutes is often regarded as a
basic strategy for the protection and survival of plants under abiotic stress (Sakamoto
and Murata, 2000 Shabala and Cuin, 2006). Many plant species accumulate
significant amounts of glycine betaine, proline, and polyols in response to high
salinity (Di Martino et al., 2003). In addition to the conventional role of these compatible solutes in cell osmotic adjustment (Bray, 1993), they are also suggested
to act as low molecular-weight chaperones, stabilizing the photosystem II complex, protecting the structure of enzymes and proteins, maintaining membrane integrity and scavenging ROS (Mansour,
1998 Noiraud et al., 2001). The production of Reactive Oxygen Species
(ROS) in cells increases during abiotic and biotic stresses like salt stress,
as does the level of ROS-induced damage. Elevated production of ROS can
seriously disrupt cellular homeostasis and normal metabolisms through oxidative
damage to lipids, protein, and nucleic acid (Bandeoglu et al., 2004). Seed
priming is a pre-sowing treatment that involves exposure of seeds to low
external water potential that limits hydration. This hydration is sufficient to
permit pre-germinative metabolic events but insufficient to allow radicle
protrusion through the seed coat. This
technique has become a common seed treatment that can increase emergence,
growth, yield and salt tolerance mainly under unfavorable environmental
conditions (Ashraf and Rauf 2001). Higher salt tolerance of plants from primed seed seems
to be the results of a higher capacity of osmotic adjustment (proline or
carbohydrate synthesis) in leaves. Sivritepe et al. (2003) confirmed
that NaCl seed priming increased proline concentration and salt tolerance of
melon seedlings. Farhoudi et al. (2007) suggested that canola seed
priming with NaCl improved salinity tolerance in canola seedlings because it
decreased cell membrane injury and increased seedling proline concentration. Seed
priming is one of the physiological methods which improve plant growth and
yield. Therefore, the present study was conducted to examine the effect of NaCl
priming on some aspects of growth and physiology, including protein, chlorophyll
and proline content of safflower under salt stress. Materials and methods The experiment was carried in the experimental field
research of Chott Mariem High Institute of Agronomy, (Tunisia) in November 2011.
Safflower seeds were primed with 5 g L-1 NaCl solution for 12 hours,
at 22 °C. After priming, primed and non primed seeds (control seeds) were sown
directly in the soil at the month of November. Throughout their vegetative
cycles, plants from primed and control seeds were irrigated with saline water
at five levels of NaCl concentrations (0, 3, 6, 9 and 12 g L-1). The
experiment was arranged as factorial in a completely randomized
design with three replications and 20 plants per replication and two factors
which were priming treatment (NaCl primed seeds and control seeds) and salinity
levels (0, 3, 6, 9 and 12 g L-1 NaCl). Photosynthetic pigments such as chlorophyll a and b
content were calculated (663 and 640 nm) according to the method of Lichtenthaler
(1987). Protein content was estimated at 595 nm according to the method of Bradford
(1976) using bovine serum albumin as standard. Free proline was estimated
at 520 nm according to the method of Bates et al. (1973) and pure
proline was used as standard. Plants were harvested at the flowering stage and were
recorded on shoot fresh and dry weight (g plant-1), shoot
chlorophyll a content (mg g-1fresh weight), shoot chlorophyll b
content (mg g-1 fresh weight), shoot chlorophyll (a + b) content (mg
g-1 fresh weight), shoot proline content (μg.g-1 fresh
weight), shoot protein content (mg.g-1 fresh weight). Growth and
biochemical parameters of safflower were evaluated with analysis of variance (ANOVA)
and Duncan multiple
range test (p NP P NP P NP P NP P NP 162a 143c 153b 135cd 141c 122e 132d 118f 124e 109g 423a 214c 312b 165d 156de 146e 143e 129f 131f 98g 158a 119c 142b 106d 109d 93e 98e 86f 77g 58h Means followed by the same
letter are not significantly different at 5% level according to Duncan test. P: Primed seed, NP: Non Primed seed Table 2. Effect of NaCl priming and salinity on
chlorophyll, proline and proteins contents of safflower under NaCl stress Treatments Chlr (a) (mg g-1
F.Wt.) Chlr (b) (mg g-1
F.Wt.) Chlr (a + b) (mg g-1
F.Wt.) Proline (μg g-1 F. Wt.) Proteins (mg g-1 F.
Wt.) Seed
Priming NaCl (g L-1) 0 3 6 9 12 P NP P NP P NP P NP P NP 1.628a 1.236e 1.532b 1.195f 1.402c 0.952fg 1.306d 0.806g 1.224e 0.671h 0.824a 0.627c 0.706b 0.514d 0.596d 0.394f 0.467e 0.271g 0.334f 0.194h 2.574a 1.914c 2.298b 1.704e 2.094b 1.692e 1.802d 1.042g 1.604f 0.834h 61.18e 52.52f 102.24d 62.02e 119.84c 104.68cd 154.67b 114.52c 196.42a 158.08b 0.385e 0.197h 0.421d 0.243g 0.474c 0.286f 0.502b 0.306ef 0.543a 0.342ef Means followed by the same
letter are not significantly different at 5% level according to Duncan test. P: Primed seed, NP: Non Primed seed Maximum shoot proline content of 196.42 μg g-1
fresh weight was recorded in plant derived from primed (P) seeds from the
treatment applied with 12 g L-1 NaCl. Minimum proline content of 52.52
μg g-1
fresh weight was recorded from plant derived from control seeds with the
application of 0 g L-1 NaCl. Highest shoot protein content was
recorded in plant derived from primed seeds with the application of 12 g L-1
NaCl (0.543 mg g -1 Fresh Weight). The Lowest shoot proteins were
observed in plant derived from control seeds with the application of 0 g L-1
NaCl (0.197 mg g-1 Fresh Weight). The treatment of seed priming has increased
shoot protein content by 35% in primed seed (P) than non primed seed (NP). Mean
values of the data revealed significant increase in shoot protein content with
the application of additional increment of salinity. Shoot protein content was
enhanced with the application of 3, 6, 9 and 12 g L-1 salinity levels,
respectively. Discussion The present study confirmed that plant height recorded
in plants derived from primed seeds were significantly different from
non-primed treatments when exposed to different salinity levels. Similar
results are also reported by Sivritepe et al. (2003) in melon. It was
observed that boosting levels of salinity has gradually decreased plant height
which might be due to decreased physiological activities resulting from water
and nutrients stress occurring under salinity stress. The adverse effect of
salinity on plants may lead to disturbances in plant metabolism, which
consequently led to reduction of plant growth and productivity (Shafi et al.,
2009). Seed priming and salinity levels have extensively affected shoot fresh
and dry weight (g plant-1) of safflower. Shoot weight decreased
progressively with the rise of stress level compared with control. Fortmeir and
Swchuber (1995) also reported similar results in barley. The increase in
salinity levels resulted in the development of water and nutrient stresses. The
toxic effect of sodium at high salt levels and physical damage to roots
decreased their ability to absorb water and nutrient which caused marked
reduction in photosynthesis, enzymatic process and protein synthesis (Tester
and Davenport, 2003), which resulted in stunted growth and poor leaf area
development. The decrease in the rate of photosynthesis due to leaf area might
be responsible to decrease shoot fresh and in turn dry weight. It is evident
from results that primed seeds in comparison with control seeds resulted in
more crop growth rate (Basra et al., 2003). Therefore, it is concluded
that seed priming could be more effective in improving safflower growth
parameters. These results agree with the finding of Harris et al. (2001)
and Basra et al. (2003). They reported greater plant weight following
seed priming. Salinity drastically affects photosynthesis due to
decreasing chlorophyll content and commonly showed adverse effects on membrane
stability (Parida et al., 2002). Salinity reduced the chlorophyll a and
b content with increasing NaCl concentrations. Increasing salinity decreased
chlorophyll content in plants (Scalet et al., 1995). Salinity caused
decreases in phototsynthetic pigment contents and photosystem II electron
transport activity in plants (Potluri and Devi Prasad, 1996). The reduction of
photosynthetic pigment in the present study might have been degradation of
chlorophyll by chlorophyllase and reactive oxygen species generated during
photorespiration under salinity. Salt induced osmotic stress as well as sodium
toxicity trigger to the formation of reactive oxygen species (ROS) such
superoxide (O2.), hydrogen peroxide (HO), hydroxyl radical (OH) and
singlet oxygen (O2-), which can damage mitochondria and chloroplast
by disrupting cellular structure (Singh et
al., 1987). It is attributed to a salt-induced weakening of
protein-pigment-lipid complex and due to the suppression of the specific enzyme
which is responsible for synthesis of green pigments (Souza et al.,
2004) or increases chlorophyllase enzyme activity (Sreenivasulu et al.,
1999). Leslie and Romani (1988) have showed that salicylic
acid seed priming treatment stimulates photosynthetic machinery and increase
the content of chlorophyll. El-Tayeb (2005) has found that Barley seeds
presoaked with 1mM salicylic acid under salinity (0, 50, 100, 150, 200 mM NaCl)
increased the photosynthetic pigment like chlorophyll ‘a’, ‘b’ and caratenoids
in shoots and roots of 15 day old seedlings compared to seedlings treated with
NaCl alone. In the present investigation, seed priming with NaCl
had maintained significantly higher total chlorophyll contents and its
fractions ‘a’ and ‘b’ compared to control which recorded highest reduction.
Similar increase in chlorophyll content has been reported by several authors,
Saha and Gupta (1998) in mungbean, Afria et al. (1998) in Gaur and
Cengiz et al. (2002) in tomato. The increase in chlorophyll content in
these treatments was attributed to decrease in chlorophyllase activity and de
novo synthesis of structural component of proteins which are responsible
for chlorophyll degradation (Subater and Rodriguez, 1978). Proline plays an important role in reducing the
injurious effects of salinity and an acceleration of the repairing processes
following stresses. Proline has already been reported to act as an
osmoprotectant and associated with mechanism of salt tolerance under salinity
stresses (Yu Lei and Shaozheng, 2000). It protects folded protein structures
against denaturation, stabilizes cell membranes by interacting with
phospholipids, functions as a hydroxyl radical scavenger, or serves as an
energy and nitrogen source (Aspinal and Paleg, 1981). Accumulation of solutes
like proline can help the plant systems to adopt in saline environment (Garcia et
al., 1997). Sivritepe et al. (2003) confirmed that, NaCl seed
priming increased proline concentration and salt tolerance in melon seedling,
under saline condition compared to non-priming seed. Farhoudi et al.
(2007) suggested that canola seed priming with NaCl improved salinity tolerance
in canola seedling because seed priming decreased seedling cell membrane damage
and increased seedling proline concentration. Recent studies suggest that
proline may play as an enzyme stabilizing role (Bhattacharjee and Mukherjee
2002 Maggio et al., 2002) and reduce lipid peroxidation (Jain et al.,
2001 Farhoudi et al., 2007) under salt stress. Our results showed that
safflower shoot from Primed group had the highest proline concentration under
the highest salinity level. Proteins that accumulate in plants under saline
conditions may provide a storage form of nitrogen that is re-utilized later (Turan
et al., 2007) and may play a role in osmotic adjustment. Proteins may be
synthesized de novo in response to salt stress or may be present constitutively
at low concentration and increase when plants are exposed to salt stress (Pareek
et al., 1997). In the present study, both salt stress and NaCl seed
priming caused an increase in shoot protein. However, this effect was more in
plant derived from primed seed than plant derived from control seed. While
working with wheat, Al-Hakimi and Hamada (2001) found that seed priming with
ascorbic acid counteracted adverse effects of salt stress by increasing leaf
soluble proteins, which protect the membrane and membrane bound enzymes (Jeng
and Sung, 1994). Thus, increased in leaf protein due to seed priming was one of
the reasons that contributed in improved growth of safflower under saline
conditions. Conclusions In conclusion, this study
showed that salt stress decrease safflower growth but NaCl priming helps plants
to decrease salt stress injury. Seed priming has positive effects on plant
height, shoot fresh and dry weights of safflower. Chlorophylls, proline and
proteins concentrations were accumulated in plants derived from primed seeds.
It has been suggested that a higher concentration of those biochemical
attributes could increase tolerance of safflower plants derived from primed
seeds to environmental stresses such as salinity. Therefore, NaCl seed priming
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