Available online at http://www.academicjournals.org/IJPPB
ISSN-2141-2162 ©2012 Academic Journals
Soil Science and Plant Nutrition (M087), School of Earth and Geographical Sciences, University of Western Australia,
Department of Agricultural Sciences, La Trobe University, Bundoora Vic 3086, Australia.
Accepted 18 February, 2012
ratio, water logging.
Soil salinity is an important constraint on plant growth.
Negative effect of salinity on plant growth is due to the
direct toxic effects of ions and osmotic stress that may
hamper a range of physiological and biochemical pro-
cesses in plants (Al-Karaki, 2000; Munns, 2002; Barrett-
Lennard, 2003; Ashraf and Harris, 2004; Munns, et al.,
2006). Salinity can directly affect plant uptake of nutrients
and may cause nutrient imbalances, due to the
competion of Na
with other nutrients such as K
, and NO
(Hu and Schmidhalter, 2005). Both Na
ions have similar chemical properties and such
similarity causes competition in uptake of these ions by
plants (Amtmann et al., 2004). This was also stated by
Schachtman and Liu (1999) that in saline soils the excess
uptake due to competitive effects.
will also improve the
resistance of the plant to salinity (Asch et al., 2000), and
*Corresponding author. E-mail: firstname.lastname@example.org.
has been used to evaluate the selectivity of ion uptake
under saline conditions and thus the ability of plants to
tolerate salt stress.
Large proportion of saline land is also subject to water
logging (saturation of the soil) because of the presence of
the shallow water-table or decreased infiltration of
surface water (Barret-Lennard, 2003, Teakle et al., 2006).
Detrimental effects of water logging on plant growth are
predominantly due to the low oxygen concentration
around roots in water-saturated soils. This is caused by
either the continuous oxygen consumption by roots and
micro-organisms present in the soil or a severely
hampered rate of oxygen diffusion from the atmosphere
to the roots (Vartapetian and Jackson, 1997; Barret-
Lennard, 2003; Teakle et al., 2006).
provenances show vary in their salinity and water logging
tolerance. However, their tolerance is inhibited by ex-
posure either to salinity or water logging especially when
both stresses happen simultaneously (Van der Moezel et
al., 1988). Unfortunately, in
logging is usually associated with salinity. Therefore, it is
necessary to study the adaptation of plants to combined
stresses of salinity and water logging. Barrett-Lennard
(2003) stated that three possible strategies of plant
adaptations to the water logging/salinity interaction are by
avoiding hypoxia through the formation of aerenchym,
reducing stomatal conductance, or by protecting
metabolism through the implementaton of salt removal
the most salt-tolerant Eucalyptus and Casuarina species
(Van der Moezel et al., 1988). Many Melaleuca species
grow in saturated soils near water bodies, often in
swamps and estuaries or in seasonal streams in arid
areas that are occasionally subjected to inundation
(Holliday, 1989; Naidu et al., 2000).
The objectives of this study were: 1) to evaluate
ecophysiological responses of three Melaleuca species to
salinity, water logging and the combined stresses; and 2)
to examine relationships among salt levels in the soil, ion
accumulation in shoots and roots, and biomass
MATERIALS AND METHODS
Soil and plant materials
Virgin brown sandy soil (Uc4.22, Northcote, 1979) was collected
soil was air-dried, sieved through a 2-mm sieve and thoroughly
mixed. The soil analyses showed that it contents 1 mg NO
mg K (NaHCO
-extractable) and 10.3 g organic carbon per kg soil
1998). The soil was then placed in polyvinyl chloride pots.
The pots (410 mm deep, 90 mm diameter) had a 20 mm layer of
gravel at the bottom. An 8 mm diameter hole was drilled through
the bottom of the pot and a piece of transparent hose was glued
into the hole. Each pot contained 3 kg of soil.
Basal nutrients were added in solution to each pot at the
following rates (mg per kg soil): KH
O (49), CuSO
O (2.5), MnSO
O (0.2), ZnSO
O (2.9), and NH
(40). After air-drying, nutrients were thoroughly mixed with the soil
by shaking in a plastic jar. NH
was added as basal fertilisation
initially as well as every 2 weeks starting in week 5 after
transplanting. Soil was watered to field capacity [11% (w/w)] with
deionised water and incubated for 2 days before planting.
Plant materials used in this experiment were three Melaleuca
species that is, (1) Melaleuca halmaturorum, a deep-rooted species
commonly found around salt lakes and brackish swamps on soils
with high clay content and with NaCl as dominant salt; it is expected
to have high tolerance to water logging and salinity; (2) Melaleuca
between sand dunes and salt flats; it is expected to have high
tolerance to salinity and moderate tolerance to water logging; and
(3) Melaleuca nesophila, commonly found on sandy soils in coastal
areas; it is expected to tolerate high NaCl concentration, but not
water logging (Holliday, 1989; Wrigley and Fagg, 1993).
For each plant species under study, treatments were arranged in a
randomised block design, involving four salt and two water logging
levels as treatments. Uniform seedlings were transplanted into pots.
In order to reduce the variation between replicate pots, two
seedlings were grown in each pot. Soil surface was covered with
alkathene beads to minimise water loss by evaporation. Pots were
weighed and soil was watered to field capacity with deionised water
every second day. Plants were grown in a glasshouse with
temperature maintained at around 23°C.
Four salt levels were used for the study, viz. 0.3, 0.8, 2.0 and 5.0
g NaCl kg
soil. Salt treatments were introduced gradually by
transplanting. After the salt treatments were fully established at the
levels planned (6
week), pots were watered to field capacity with
imposed on day 91 by connecting a hose at the bottom of pot to a
container filled with deionised water; the water level was maintained
at 2 cm above the soil surface.
Shoot height was measured weekly starting from the first week after
119 days (M. halmaturorum and M. nesophila) after transplanting.
Roots were separated from the soil by sieving through a 4-mm
sieve. Roots were then rinsed with deionised water and dried at
70°C for 48 h. Shoot fresh weight was determined after drying at
70°C for 48 h.
Concentration of Na
in dried shoots and roots were
determined using atomic absorption spectrometry (AAS) after
digestion in hot concentrated nitric acid as outlined by Reuter et al.
(1986). Sub-samples of 0.5 g each were placed in 50 mL flasks and
10 mL of concentrated nitric acid added. The mixture was first
heated on fry pans to 90°C for 30 min, and then temperature
increased to 140°C to remove excess nitric acid. De-ionised water
was added to make up to the 23 mL volume of the primary extract.
An aliquot of this primary extract was diluted for determination of
), potassium (K
) and calcium (Ca
interferences, a solution of lanthanum oxide (La
each diluted extract to give a lanthanum content of 0.1% (w/w). The
ratios were calculated for shoots and roots
under different salinity levels. Chloride was extracted in hot water
by shaking for 48 h followed by measurement using a chloride-
A two-way analysis of variance (ANOVA) was conducted using
compare the main effects and interactive effects combined salinity
and water logging stress on shoot biomass, root biomass, plant
height and Na
treatments were separated by the Fisher’s protected least
significant difference (LSD) test at a significance level of 5%.
By the time of harvest, dry weights of shoots and roots of
salinity levels (Table 1). For example, shoot dry weight of
plants grown at 5 g NaCl kg
soil decreased to 30, 50,
commenced on day 28.
(g NaCl kg
Shoot dry weight (g/pot)
Shoot dry weight (g/pot)
Values in a column followed by different letter showed significantly different at P = 0.05.
and 11% of the 0.3 g NaCl kg
treatment for M.
respectively. Comparable values were obtained
for the root growth decrease as a consequence of
increasing salinity (Tabel 1). Melaleuca species
were not affected by water logging treatment,
except that M. thyoides died after 1 week of being
subjected to water logging at high salt level (5 g
Tissue mineral concentration
The three Melaleuca species differed in their
interaction between water logging and salinity was
observed for sodium (Na
) and chloride (Cl
tissue concentration in M. halmaturorum, M.
when grown in water logging soil compared with
ficantly with increasing salinity level (Table 2). Na
concentration in shoots grown at 5 g NaCl kg
compared with values obtained at 3 g NaCl kg
soil for M. halmaturorum, M. thyoides, and M.
there was no difference in root concentration of
regardless the NaCl treatment, with shoot Na
concentration increasing only at 5 g NaCl kg
concentration in the water logging
especially at 2 and 5 g NaCl kg
were evident for the Cl
concentrations in shoots
concentrations in roots and
increased with increasing salinity levels, both for
water logging or non-waterlogged treatment
(Table 2). Higher Cl
concentration was observed
The shoot K
concentration was affected by the
(Table 2). For example, shoot K
among NaCl treatments, whereas under the non-
waterlogged treatments shoot K
lower than those in the 0.3 and 0.8 g NaCl
treatments. For M. thyoides, the shoot K
for the 0.3, 0.8, 2 and 5 g NaCl treatments Under
the non-waterlogged condition the shoot K
increased NaCl level. The trend in shoot K
concentration in M. nesophila was reversed
Under both waterlogged and non-waterlogged
conditions the shoot K
concentration in the 5 g
other NaCl treatments. The concentration of K
concentration compared with other
The significant interaction between water
logging and salinity with respect to the Na
ratio in shoots were observed in shoot of M.
higher when plants were grown in the waterlogged
) Chloride (Cl
), and potassium (K
) concentration in shoots and roots of three Melaleuca species grown under different salinity (NaCI) levels at field capacity or with
Within the eight combinations of salt x water logging treatments for each species, means followed by different letter indicated significant difference at 0.05 significance level.
Salt level (g NaCl/kg soil)
ratio in shoots and
roots of Melaleuca thyoides (grown for 105 days), Melaleuca halmaturorum and
Melaleuca nesophila grown for 119 days, respectively, in soil columns. Salinity
treatments commenced on day 28 and water logging commenced on day 91. Values
followed by the same letter are not different at P=0.05
compared with the control (field capacity) soil (Figure 1).
This interactive effect also observed in M. thyoides root.
This study demonstrated that Melaleuca species were
and salinity. This interaction affected the accumulation of
and M. nesophila shoots. Similar studies on other plant
species have shown that the combination of water
logging and salinity is considerably more detrimental than
the single stress alone, especially at increasing salinity
(Meddings et al., 2001, Barrett
Lenard, 2003, Teakle et
and was higher in water logging compared with non-
water logging treatment. This could be due to reduced
control of Na
intake as a result of the damage to the cell
mechanisms, especially under high NaCl concentration.
Such disruptions might also have decreased selectivity
compared with Na
, thus facilitating accumulation
without equivalent uptake of K
required to main-
tain an optimum ion balance for metabolic processes.
The increase in salt accumulation due to salinity and
water logging was likely to be caused by increased
passive uptake of Na
through damaged membranes
in active exclusion mechanisms (Thomson et al., 1989).
However, this was not the case for M. halmaturorum and
M. nesophila roots, indicating that different species of
Melaleuca have different responses to salinity and water
In this study, all the Melaleuca species survived, even
though the stem elongation and dry matter accumulation
were reduced with increasing saline levels. This result
supports the previous studies reporting an adverse effect
on stem elongation due to increasing NaCl concentration
(Tozlu et al., 2000). M. thyoides appeared relatively more
tolerant to salinity than M. halmaturorum and M.
nesophila. The more tolerance of M thyoides might be
due to genetically characteristric of the plant (Marcar et
al., 1995). The plant height of M. thyoides was not
at 5 g NaCl kg
soil. The decline in shoot biomass of M.
whereas root growth was not affected. However, biomass
production of M. halmaturorum and M. nesophila was
decreased even under low salinity (2 g NaCl kg
concentration in roots and shoots of three
except in M. nesophila roots. These results suggest that
there is no blocking or exclusion mechanism for accumu-
lation of Na
. In general, the accumulation of Na
was greater in roots of M. halmaturorum and M. thyoides
capacity to sequester salt in roots, thus minimizing the
exposure of leaf cells (containing photosynthetic
apparatus) to high concentration of salt (Garg and Gupta,
1997). On the contrary, this was not the case for M.
nesophila, supporting differential salinity resistance within
Beside the increase in Na
with increasing salinity, the strongest effect of salinity in
this experiment was manifested in the Na
increased both in shoots and roots of Melaleuca species,
except in M. nesophila roots. The high Na
are consistent with those reported in Taxodium distichum
(Allen et al., 1996), Poncirus trifoliata (Tozlu et al., 2000) and
Aini et al. 57
concentration) and successively lower redox potentials
(Barrett-Lennard, 2003). The earliest responses to water
logging are reduced water absorption and transpiration.
Further responses may include decreased root and shoot
growth, reduced mineral uptake, causing premature leaf
senescence,abscission, and shoot dieback (Kozlowski
and Pallardy, 1997). Our results demonstrated that
biomass of three Melaleuca species was not affected by
water logging for up to 4 weeks, except decreased root
growth of M. halmaturorum and M. thyoides in the water
logging treatment. Nevertheless, the Na
significantly higher in waterlogged compared with non-
waterlogged treatments. These results indicate that water
logging reduces the selectivity for K
relative to Na
Hypoxia condition also most likely caused a significant
from the root, as evidenced by lower K
concentration in the roots, especially for M. thyoides.
where 80% loss of K
from roots occurred under hypoxia
Melaleuca species exhibit differential salinity resistance.
Water logging increased the uptake of Na
species levels of tolerance are drastically reduced when
plants are subjected to water logging. This has
implications in rehabilitation of saline-waterlogged lands,
using Melaleuca species.
Funding for this research was provided by the Co-
operative Research Centre for Plant-Based Management
of Dryland Salinity. Thanks to Michael Smirk, Paul
Damon and Lorraine Osborne for assistance with sample
preparation and analyses.
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