International Research Journal of Plant Science (ISSN: 2141-5447) Vol. 1(5) pp. 126-132, November, 2010
Available online http://www.interesjournals.org/IRJPS
Copyright © 2010 International Research Journals
Full Length Research Paper
Identification of salt tolerance in seedling of maize (Zea
mays L.) with the cell membrane stability trait
M.B. Collado*, M.J. Arturi, M.B. Aulicino, M.C. Molina1
Instituto Fitotécnico de Santa Catalina. Facultad de Ciencias Agrarias y Forestales. Universidad Nacional de La Plata.
Garibaldi 3400, Llavallol (1836). Buenos Aires, Argentina. 1CONICET.
Accepted 22 September, 2010
The development of salt tolerant crop plants is an important breeding objective. In this paper we study
the usefulness of cell membrane stability for screening maize under salinity and their relationship with
the different mechanisms of tolerance. Two tolerant lines were probed in two treatments: non saline
(without NaCl), and saline (150mM NaCl). Seedlings were harvested every seven days. The lengths of
shoot, root and the number of expanded leaf were recorded. The dry mass of shoot and root were
determined. Cell membrane stability was estimated on: 2nd, 3rd and 4th leaf and root by the Injury Index
(Ii). The Ii of 3rd leaf at 14 days and Ii measured on 4th leaf at 28 days showed differences in both
genotypes in both treatments. These results, confirm the usefulness of measurement of the Membrane
Stability to identify tolerance to saline stress. F564 had greater shoot growth and less membrane
damage in its leaves than SC75. The greater growth seems to indicate less accumulation of Na+ and is
associated to the Na+ exclusion mechanism, while SC75 seems to tolerate less Na+ in its shoot,
associated with tissue tolerance.
Key words: Zea; salinity; seedling growth; cell membrane stability; mechanism of salt tolerance.
INTRODUCTION
Several abiotic stresses affect the crop productivity. Soil
salinity is an increasing problem of world-wide concern in
arid regions. The development of salt tolerance cultivars
has been proposed as the most effective strategy to
overcome this problem (Epstein and Rains, 1987). The
resistance to abiotic stress in general and to salinity
stress in particular is under polygenic control (Flowers
and Yeo, 1995). In consequence, the identifying of
genetic variability related to this trait is complicated. In
early stages of a breeding program for improving stress
tolerance the number of genotypes to be evaluated is
usually high. Then, for identification and selection of
superior genotypes a reliable, easy to measure and of
low
cost
trait
is
specially
required.
Three potential physiological effects are produced on the
plants for the salinity: lowering of the water potential,
+
direct toxicity of Na and Cl absorbed and interference
with the uptake of essential nutrients (Flowers and
Flowers, 2005).
*Corresponding author E-mail :maulicino@agro.unlp.edu.ar;
Tel. /Fax: 0054-11-4282-0233.
The adaptation to salinity could be classified in three mechanisms: tolerance to osmotic stress (not specific to
salinity and associated with water stress); Na+ exclusion
from leaf blades (Na+ is accumulated in the root
protecting the leaves from toxic levels of salt) and tissue
+
tolerance
to
accumulated
Na
(the
ion
is
compartmentalized at cellular and intracellular level to
avoid toxic concentration within the cytoplasm) (Munns,
2005; Munns and Tester, 2008). These three
mechanisms would be under different genetic control (Hu
et al., 2007; Munns and Tester, 2008; Pardo et al. 2006;
Suriyan et al., 2009; Tester and Davenport, 2003). The
identification of genotypes with different tolerant
mechanisms and their subsequent crossing could be
applied in breeding programs that improve the global
response to salt stress by the use of “stacked and
pyramided traits”. Munns (1993) has proposed a biphasic
model of growth reduction in response to salinity. The
osmotic phase produces a reduction due the salt outside
the root rather than inside the plant. The ionic phase
produces a reduction as consequence of an increase of
the salt concentrations in the cell wall or cytoplasm when
vacuoles can no longer sequester incoming salts.
Collado et al. 127
Maize (Zea mays L.) is the third most important cereal in
the world after wheat and rice, and grows under a wide
range of climatic conditions. It is moderately sensitive to
salinity and considered as the most salt-sensitive of the
cereals (Maas and Hoffman, 1977; Ashraf and McNeally,
1990). Besides, maize is a highly cross-pollinated crop. In
consequence, it has become highly polymorphic for the
natural and domesticated evolution and thus contains
enormous variability (Paterniani, 1990; Maiti et al., 1996)
in which salinity tolerance may exist. The response to
salinity varies with the stage of development of maize
plant (Maas and Hoffman, 1983; Pasternak et al., 1985).
Tolerance to stresses as salinity of plants can be
determined by using different growth parameters like root
length, shoot length, dry mass of root and shoot (Cicek
and Cakirlar, 2002). Several other physiological
characteristics have been reported as being reliable
indicators for the selection of germplasm possessing high
degree of salinity tolerance. These include seed
germination, the degree of electrolyte leakage (cell
membrane stability, CMS) from salinity-damaged leaf
cells and the water relations of plants (Ashraf, 2004 a
Ashraf and Harris, 2004 b).
The primary site of injury under stress conditions is the
plasmalemma (Levitt, 1980). The membrane integrity is
altered for the stress; a consequence of this is the
increase of the cell permeability which is accompanied by
electrolyte leakage from the cell (Blum and Ebercon,
1980). The test to detect the integrity of cell membrane is
called Cell Membrane Stability (CMS) and was used to
characterize drought resistance in plants (Bandurska,
2000; Farooq and Azam, 2002; Gavuzzi et al., 1997;
Hubac et al., 1989; Premanchandra et al., 1989;
Venkateswarlu and Ramesh, 1993). This trait has been
recently used as a reliable and effective selection
criterion for identify salinity tolerance in wheat (Farooq
and Azam, 2006; Sairam et al., 2002).
Salinity changes the composition and/or structure of the
plasma membrane in the plants. These alterations were
different in salt sensitive and tolerant species and
cultivars (Mansour and Salama, 2004; Mansour et al.,
2005).
The change in plasmatic membrane permeability
occurs before visual toxic symptoms of salinity. In
consequence, the CMS technique could be a good
indicator for salt stress and tolerance, and therefore could
be recommended as a reliable selection criterion for
developing salts tolerant genotypes.
The objectives were to study the effectiveness and
reliability of physiological techniques such as CMS for
screening maize genotypes under high salinity and the
relation of this trait with the different mechanisms of
tolerance to salinity.
MATERIAL AND METHOD
Plant materials and growth conditions
Seeds of the two tolerant inbred lines: SC75 and F564 (Collado et
al., 2010) were surface sterilized in 1% sodium hypochlorite
solution for 5 minutes before experimentation, then rinsed with
distilled water. The caryopses were germinated in Petri dishes with
moistened filter paper in a dark incubator at 26 ºC during five days.
In the sixth day of germination, three uniformly germinated
seedlings were transferred to pots containing perlite. These pots
were put in trays with nutrient solution. The half strength
Hoagland´s solution was used as main culture solution. The
solutions were renewed every three days. The experiment was
carried out in a controlled environment room at 25 ºC, with 16h day
length. All conditions were maintained constant during the growth
period. Two environments were used: non saline treatment where
no NaCl solution was added and the other treatment receiving 150
mM NaCl. The final concentration was reached by a gradual
increment of 37.5 mM NaCl every day (Cicek and Cakirlar, 2002;
Khan and McNelly, 2005; Rao and McNelly, 1999). A completely
randomized design with 4 replicates was adopted. The seedlings
were harvested in regular time period: 7, 14, 21 and 28 days of both
treatments and in each date several traits were recorded.
Growth analysis
The lengths for shoot, radicle (SL, RL, respectively) and the number
of expanded leaf (LN) were recorded. Shoot and radicle were
separated and the samples were dried at 80ºC for two days until
constant weight, for dry mass determination (SDM and RDM
respectively). Relative dry mass (SDM/RDM) and relative length
(SL/RL) were calculated.
Electrolyte leakage measurement
The cell membrane stability was estimated on several tissues: 2nd,
3rd and 4th leaf and root. The 2nd and 4th leaf were measured in
three dates and the 3rd leaf and root in four dates. A piece of the
different organs evaluated were cut, weighted and washed with
distilled water to remove the solution from tissue, then the samples
were immersed in 10ml of distilled water and placed for incubation
at 10ºC for 24h (Mansour and Salama, 2004; Mansour et al., 2005).
After incubation samples were equilibrated to room temperature.
Then, the conductivity of the medium was recorded (EC1) in: 2nd
leaf (EC1L2), 3rd leaf (EC1L3), 4th leaf (EC1L4) and root (EC1R).
The samples were autoclaved for 15 min to kill all tissues, and after
that cooled to room temperature. The conductivity of the solutions
was read again (EC2) in all tissues analysed: EC2L2 (2nd leaf),
EC2L3 (3rd leaf), EC2L4 (4th leaf) and EC2R (root). The electrolyte
leakage was measured with a conductometer (Consort C931) and
expressed in µS/cm. Injury Index was calculated as: Ii = (EC1/ EC2)
× 100 ( Sairam et al, 2002; Tas and Basar, 2009)
Stastical analysis
The data were subjected to a factorial analysis of variance with two
genotypes, two treatments and four dates. The means were
compared by Least Significant Differences (LSD) at the 0.05
probability level. The variables SL, RL, LN, SDM and RDM were
transformed to natural logarithm to equalize the variances (Sokal
and Rolf, 1995).
RESULTS
The morphological traits that were measured showed
significant and very significant differences for dates,
128 Int. Res. J. Plant Sci.
Table 1: Analysis of variance of: Root Length (RL, cm), Shoot Length (SL, cm), Number of expanded leafs (Ln.), Shoot Dry Masses (SDM, mg), Root Length (RL, cm), Root Dry
Masses (RDM, mg), measured in Maize seedling grown under saline and non saline conditions.
Sources of variation
Date
Treatments
Genotypes without salt
Genotypes with salt
Salt vs Control
Date x Treatment
Error
Mean squares
df
RL
3
0.047ns
SL
0.071**
LN
0.764**
SDM
5.122**
RDM
1.369**
SDM/RLM
1.317**
SL/RL
0.705**
3
1.597**
0.013**
0.034**
0.10ns
0.69**
0.34**
0.73**
1
1
1
9
0.016ns
0.075ns
4.701**
0.216**
0.0001ns
0.0001ns
0.038**
0.004**
0.010ns
0.0001ns
0.093**
0.0202**
0.076ns
0.14ns
0.099ns
0.103ns
0.191ns
0.07ns
1.86**
0.181*
0.01ns
0.1ns
0.91**
0.098*
0.012ns
0.067ns
2.051**
0.059*
48
0.029
0.001
0.007
0.109
0.075
0.096
0.028
**,*, indicates differences significant at p <0.01; 0.05 respectively, while ns, denotes not significantly differences.
treatments and date x treatment interaction.
However, some exceptions were found: SDM did
not show differences regarding treatment nor date
x treatment interaction, whereas RL did not show
differences regarding date (Table 1). All the
characters showed significant differences (p<0.01)
when the saline and control treatments were
compared, with the exception of SDM (Table 1).
The saline treatment dramatically reduced the
expression of the morphological traits that were
measured, except for the SDM/RDM and SL/RL
ratios, which showed higher recordings under
saline treatment (Figure. 1e and 1f). Both
genotypes showed significant differences (p<0.05)
in their behaviors when they grew in saline
conditions, in comparison with their corresponding
controls, after 21 days of treatment for RL, SL, LN
and Ratio Length (SL/RL) (Figure. 1a, 1b, 1c, 1f).
RL showed significant differences (p<0.05) in both
genotypes after 14 days, although in the SC75
genotype the differences appeared after 7 days
(Figure. 1a). RDM showed significant differences
after 28 days for treatment in both genotypes
(Figure. 1d). Nevertheless, F564 also showed
differences after 21 days (Figure. 1d). SDM did
not show significant differences in the treatment of
both genotypes. Among the evaluated characters,
RL was the one that suffered the biggest losses
throughout the 4 dates (Figure. 1a). In both
genotypes the losses in root length varied from 14
to 58 %. RDM showed major losses in both
genotypes under salt, in F564 the losses varied
from 10 and 56%; and in SC75 they were
between 17 and 47% for the four dates. As the
losses were increasing during the experiment the
biggest ones were recorded at 28 days. It can
also be observed that both genotypes did not
show significant differences between each other
in the saline treatment in any of the traits that
were screened. Nevertheless, the Least
Significant Difference Test showed that genotype
F564 had a greater SDM/RDM ratio than SC75
(Figure. 1e). The Injury Index (Ii) associated with
membrane stability showed significant or highly
significant differences for date, treatment and date
x treatment interaction, with the exception of IiL2
which did not show differences neither for
treatment nor for date x treatment interaction
(Table 2). When control and salt treatments were
compared, highly significant differences were
found only for the Ii measured on 2nd Leaf and
Root. The comparison between genotypes in
saline conditions showed highly significant
differences for Ii measured on 3rd an 4th leaves
(Table 2). The Ii measured on 2nd leaf (IiL2) did
not prove to be very informative; the evolution of
the injury Index trait was similar in both genotypes
and treatments (Figure. 2a). The IiL3 for the first
date were similar for both genotypes in both
treatments.
After 14 days of salinity each
genotype showed significant differences in both
treatments. At 21 and 28 days, only SC75 showed
significant differences between treatments (Figure
2b). The IiL4 showed significant differences in
both genotypes for treatments at 14 days and 28
days (Figure. 2c). The IiR showed significant
differences in both genotypes for treatments at
two first weeks. Besides, SC75 y F564 showed
significant differences between treatments at 21
and 28 days, respectively (Figure. 2d). Under the
saline treatments, both genotypes showed a
rd
different behavior in their Ii of 3 leaf at 14 and 21
Collado et al. 129
nd
rd
th
Table 2: Analysis of variance of Injury Index in: 2 Leaf (IiL2), 3 Leaf (IiL3), 4 Leaf (IiL4) and Root (IiR), measured in
Maize seedling grown under saline and non saline conditions.
Sources of variation
Mean squares
Date
IiL2
987.9*
IiL3
2810.7**
IiL4
3355.1**
IiR
60.6**
Treatments
710.2ns
541.4**
663.1**
196**
Genotypes without salt
73.3ns
99.9ns
1048.1**
23.73ns
Genotypes with salt
Salt vs Control
Date x Treatment
Error
85.2ns
1972.4**
136.4ns
1520**
43.4ns
1353**
731.1**
146.8ns
877.4**
0.593ns
566.3**
42.2**
263.4
108.6
64.1
8.06
**,*, indicates differences significant at p <0.01; 0.05 respectively, while ns, denotes not significantly differences.
Figure. 1. Effect of 150 mM NaCl (open symbols) and 0 mM NaCl (closed symbols) in: a) Root Length (RL),
b) Shoot Length (SL), c) Leaf expanded Number (LN), d) Root Dry Masses (RDM), e) Ratio of SDM/RDM
and f) Ratio SL/RL in SC75 ( , ) and F564 ( , ) at 7, 14, 21 and 28 days of treatments. The Letter A
indicates significant differences for the genotypes F564 in both treatments; the B indicates significant
differences for the genotypes SC75 in both treatments, C indicates significant differences between
genotypes in saline treatment, ns denote not significant differences (LSD, p < 0.05).
130 Int. Res. J. Plant Sci.
Figure. 2. Effect of 150 mM NaCl (open symbols) and 0 mM NaCl (closed symbols) on Injury Index (Ii) in: a)
2nd Leaf (IiL2), b) 3rd Leaf (IiL3), c) 4th Leaf (IiL4) and d) Root (IiR) for SC75 ( , ) and F564 ( , ) at 7, 14, 21
and 28 days of treatments. The Letter A indicates significant differences for the genotypes F564 in both
treatments; the B indicates significant differences for the genotypes SC75 in both treatments, C indicates
significant differences between genotypes in saline treatment, ns denote not significant differences (LSD, p <
0.05).
days and in the 4th at 28 days.
DISCUSSION
Several traits of seedling were employed to identify
tolerance to salinity in maize. In that respect, the length of
root of seedlings grown in control and saline solutions
was broadly used; when the seedlings were exposed to
salinity the root growth was rapidly reduced (Khan and
McNelly, 2005; Rao and McNelly, 1999). In accordance
with that, our findings show that RL was the one of the
morphological characters that suffered major losses in
comparison with the non-saline treatment throughout the
four dates of screening. Besides, this trait was
immediately affected by the salt, since at 7 days
significant differences were observed with the controls (0
mM ClNa) in the SC75 genotype (Figure. 1a). This
behavior is expectable, because the root is the first organ
that is in contact with the salt and is the first to be
affected.
Eker et al. (2006) pointed out that under salt stress,
measurement of shoot length may be a more effective
and useful parameter than root length to identify salinity
tolerance. Accordingly, our results also showed an
important reduction in SL after 21 days in salinity
compared to the controls and this trait could be useful in
screening salinity tolerance (Figure. 1b).
The number of leaves was also an important trait to
differentiate the genotypes in both treatments, at 21 days
of salinization the employed genotypes showed
significant differences with controls (Figure. 1c). This
behavior which seems to indicate a reduction in the
appearance of new leaves could be associated with the
osmotic stress pointed out by Munns et al. (1995), (2002)
and Munns and Tester (2008) in the biphasic model of
growth reduction due to salinity. The osmotic stress
occurs during the early hours of salt exposure and affects
the plant while osmotic potential differences remain.
The ratio SDM/RDM was significantly higher in the
treatment under salt in relation to the controls at 28 days
on both genotypes (Figure. 1e). This means that an
active shoot growth was maintained and it would reduce
+
the rate of accumulation of Na in leaves to maintain a
high proportion of photosynthesizing tissue. Among the
+
tolerance strategies, the low accumulation of Na in shoot
+
is associated with the Na exclusion mechanism (Munns
et al., 2002; Munns and Tester, 2008). Our findings seem
Collado et al. 131
to evidence the presence of this mechanism in the maize
genotypes that were tested. On the other hand, our
findings do not coincide with those obtained by Mansour
et al. (2005), which evidenced a greater reduction in the
dry mass relation between the shoot and root of a
tolerant maize genotype, in comparison with the sensitive
genotype treated with 150 mM ClNa. These authors
stated that the greater reduction of the tolerant genotype
could be related to an adaptation response to salinity, in
order to save energy that would be used to maintain the
normal metabolism of the plant. The higher ratio
SDM/RDM showed in F564 (p<0.05) than in SC75, for
saline treatments at 28 days, could be indicating that in
this genotype an intense rhythm of grow of shoot
maintain a lower accumulation of Na+ and protected it of
deleterious effects of this ion (Figure. 1e).
The Injury Index (Ii) measurements were different
depending on the tissue where were made. The Ii
recorded on third and fourth leaves and root showed a
different behavior in both treatments and both genotypes
and could be considered to be a reliable salinity tolerance
estimator (Figure. 2b, 2c and 2d). Furthermore, both
genotypes are tolerant and could be seen that Ii
measurements in saline treatment showed a differential
behavior for 3rd and 4th leaves. At the 3rd leaf the Ii of
F564 was higher (p<0.05) at 14 and 21 days than in
SC75, while on the 4th leaf at 28 days the situation was
the opposite (Figure. 2b and c). Due to the membrane
+
damage and the Na accumulation were increased
rd
(especially in 3 leaf), we could conclude that rhythm of
growth in F564 was initially affected by salt stress.
However, at 28 days the intensive rate of growth should
have determined a dilution effect on the concentration of
Na+ in tissues. While SC75 maintained the rate of growth,
the leaf damage was less perhaps due to the tolerance of
the tissue (Figure. 2b and 2c).
Salt stress generates an ionic imbalance which causes
an alteration of membrane permeability. The
determination of Membrane Stability could reflect the
ionic content of the plant (Ghoulam et al., 2002; Munns et
al., 2002). Thus, the positive correlations between Ii and
+
+
Na and the negative correlation with K mentioned in the
work carried out by Ferreira-Silva et al. (2008) could be
used so as to identify what tissues Na+ accumulated in
first. Besides, the salinity stress increases the Hydrogen
peroxide accumulation and the lipid peroxidation. It
provoked a significant decrease in the stability
membrane. The decrease in membrane stability has
been used as indices of salt injury and salt tolerance in
Amaranthus sp. (Battacharjee et al., 1996; Dhindsa et al.,
1981). In consequence, the Membrane Stability
measurement could be employed like an indicator the
ionic and oxidative states of the plants grow in saline
treatments. However, we believe that further studies are
needed to confirm the useful of the character of
membrane stability as a criterion for selection of maize
genotypes against salinity stress.
CONCLUSION
Membrane stability appears as a promising trait in the
identification of salinity tolerance in maize seedlings. This
character has the advantage of being an indestructible
measurement (it can be determined on a piece of tissue)
in a rapid, economical and simple way. This aspect is of
utmost importance since it apparently allows employing
the Membrane Stability trait in the selection of salinity
tolerant entries in Breeding Programs, where the number
of genotypes that are screened is generally high.
Based on our findings, Ii recorded on the 3rd leaf at 14
days or in 4th leaf at 28 days; could be employed like
reliable traits in the identification of salinity tolerance in
maize seedlings. On the other hand, this character
allowed us to analyze aspects that are associated with
different mechanisms or strategies of tolerance.
References
Ashraf M (2004a). Some important physiological selection criteria for
salt tolerance in plants. Flora 199:361–376.
Ashraf M, Harris PI (2004b). Potential biochemical indicators of salinity
tolerance in plants. Plant Sci. 166:3–16.
Ashraf M, Mc Neally T (1990). Improvement of salt tolerance in maize
for selection and breeding. Plant Breed. 104:101-107.
Bandurska H (2000). Does proline accumulated in leaves of water
deficits stressed barley plants continue cell membrane injury? I Free
proline accumulation and membrane injury index in drought and
osmotically stressed plants. Acta Physiol. Plant. 22:409-415.
Battacharjee S, Mukherjee AK (1996). Ethylene evolution and
membrane lipid peroxidation as indicators of salt injury in leaf tissues
of Amaranthus seedlings. Indian J. Exp. Biol. 34:279-281.
Blum A, Ebercon A (1980). Cell membrane stability as a measure of
drought and heat tolerance in wheat. Crop Sci. 21:43–47.
Cicek N, Cakirlar H (2002). The effect of salinity on some physiological
parameters in two maize cultivars. Bulg. J. Plant Physiol. 28:66-74.
Collado M, Aulicino M, Molina M, Arturi M (2010). The use of electrolyte
leakage in the evaluation of salinity tolerance at seedling stage in
maize (Zea mays L.). Maize Genet. Coop. Newsletter 84.
Dhindsa RS, Plumb-Dhindsa P, Throne TA (1981). Leaf senescence:
correlated wilh increased levels of membrane permeability and lipid
peroxidation and decreased levels of superoxide dismutase and
catalase. J. Exp. Bot. 32:93-101.
Eker S, Cömertpay G, Kdnuskan O, Ülger A, Öztürk L, Cakmak I
(2006). Effect of salinity stress on dry matter production and ionaccumulation in hybrids maize varieties. Türkish Journal of Agric. and
Forestry 30:365-373.
Epstein E, Rains DW (1987). Advances in salt tolerance. Plant & Soil
99:17-29.
Farooq Shafqat and Farooqe Azam (2002). Production of low input and
stress tolerance wheat germoplasm through the use of biodiversity in
wild relative. Hereditas 135:211-215.
Farooq S and Azam F (2006). The use of cell membrane stability (CMS)
technique to screen for salt tolerant wheat varieties. J. Plant Physiol.
163:629- 637.
Ferreira-Silva S, Silveira J, Voigt E, Soares L, Viegas R (2008).
Changes in physiological indicators associated with salt tolerance in
two contrasting cashew rootstocks. Braz. J. Plant Physiol. 20:51-59.
Flowers TJ, Flowers SA (2005). Why does salinity pose such a difficult
problem for plant breeders?. Agric. Water Maneg. 78:15-24.
Flowers TJ and Yeo AR (1995). Breeding for salinity resistance in crop
plants: where next? Australian Journal of Plant Physiology 22:875884.
Gavuzzi P, Rizzo F, Palumbo M, Campanille R, Ricciardi G, Borghi B
(1997). Evaluation of field and laboratory predictors of
132 Int. Res. J. Plant Sci.
drought and heat tolerance in winter cereals. Can. J. Plant Sci.
77:523–531.
Ghoulam C, Foursy A, Fares K (2002). Effects of salt stress on growth
inorganic ions and proline accumulation in relation to osmotic
adjustment in five sugar beet cultivars. Environ. Exp. Bot. 47:39-50.
Hu Y, Burucs Z, von Tucher S, Schmidhalte U (2007). Short-term
effects of drought and salinity on mineral nutrient distribution along
growing leaves of maize seedlings. Environ. and Exp. Bot. 60: 268–
275.
Hubac C, Guerrier D, Ferran J, Tremolieres A (1989). Change of leaf
lipid composition during water stress in two genotypes of Lupinus
albus resistant or susceptible to drought. Plant Physiol. Biochem.
27:737-744.
Khan AA, Mcneilly T (2005). Triple test cross analysis for salinity
tolerance based upon seedling root length in maize (Zea mays L.).
Breeding Science 55:321-325.
Levitt J (1980). Responses of Plant to Environment Stresses Water,
Radiations, Salt and other stresses. Vol. 2 Academic Press, New
York.
Maas EV, Hoffman GJ (1977). Crop salt tolerance current assessment.
J. Irrig. & Drain Div. ASCE. 103:115-134.
Maas EV, Hoffman GJ (1983). Salt sensitivity of corn at various growth
stages. California Agriculture 37:14-15.
Maiti RK, Amaya LE, Cardona SI, Dimas AM, De La Rosa-Ibarra M,
Castillo HD (1996). Genotipyc variability in maize cultivars (Zea mays
L.) for resistance to drought and salinity. J. Plant Physiol. 148:741744.
Mansour MM, Salama KH (2004). Cellular basis of salinity tolerance in
plants. Environ. Exp. Bot. 52:113-122.
Mansour MM, Salama KH, Ali FZ, Abou Hadid AF (2005). Cell and plant
response to NaCl in Zea Mays L. cultivars differing in salt tolerance.
Gen. Appl. Plant Physiology 31:29-41.
Munns R (1993). Physiological processes limiting plant growth in saline
soils: some dogmas and hypotheses. Plant, Cell and Environment
16:15-24.
Munns R, Schachtman DP, Condon A (1995). The significance of twophase growth response to salinity in wheat and barley. Australian
Journal of Plant Physiology 22:561-569.
Munns R, Husain S, Rivelli A, James R, Condon AG, Lindsay M,
Lagudah E, Schachtman DP, Hare R (2002). Avenues for increasing
salt tolerance of crops, and the role of physiologically based selection
traits. Plant and Soil 247:93-105.
Munns R (2005). Genes and salt tolerance: bringing them together.
New Phytologist 167:645-663.
Munns R, Tester M (2008). Mechanisms of salinity tolerance. Annu.
Rev. Plant Biol. 59:651-681.
Pardo J, Cubero B, Leidi E, Quintero F (2006). Alkali cation exchangers:
roles in cellular homeostasis and stress tolerance. J. Exp. Bot.
57:1181-99.
Pasternak D, De Malach Y, Borovic I (1985). Irrigation with brackish
water under desert conditions. II. Physiological and yield response of
maize (Zea mays) to continuous irrigation with brackish water to
altering brackish-fresh-brackish water irriation. Agricultural Water
Management 10:47-60.
Paterniani E (1990). Maize breeding in tropic. Cri. Rev. Plant Sci. 9:125154.
Premachandra GS, Saneoka H, Ogata S (1989). Nutrio-Physiological
Evaluation of the Polyethylene Glycol Test of Cell Membrane Stability
in Maize. Crop Sci. 29:1287-1292.
Rao SA, Mcneilly T (1999). Genetic basis of variation for salt tolerance
in maize (Zea mays L). Euphytica 108:145-150.
Sairam RK, Rao KV, Srivastava GC (2002). Differential response of
wheat genotypes to long term salinity stress in relation to oxidative
stress, antioxidant activity and osmolyte concentration. Plant Science
163:1037-1046.
Sokal RR, Rolf FJ (1995). Biometry, Third ed. W.H. Freeman and Co.
New York.
Suriyan
Cha-um,Thippawan
Trakulyingcharoen,
Prasartporn
Smitamana and Chalermpol Kirdmanee (2009). Salt tolerance in two
rice cultivars differing salt tolerant abilities in responses to isoosmotic stress. Austr. J. Crop Sci. 3:221- 230.
Tas B, Basar H (2009). Effects of various salt compounds and their
combinations on growth and stress indicators in maize (Zea mays L.).
African J. Agric. Research 4:156-161.
+
+
Tester M, Davenport R (2003). Na transport and Na tolerance in
higher plants. Ann. Bot. 91:503-527.
Venkateswarlu, B, Ramesh K (1993). Cell membrane stability and
biochemical response of cultured cells of groundnut under
polyethylene glycol-induced water stress. Plant Sci. 90:179–185.