Research Journal of Environmental and Earth Sciences 4(11): 990-995, 2012
ISSN: 2041-0492
© Maxwell Scientific Organization, 2012
Submitted: August 31, 2012
Accepted: October 02, 2012
Published: November 20, 2012
Salinity Effects on Growth Attributes Mineral Uptake, Forage Quality and Tannin
Contents of Acacia saligna (Labill.) H. Wendl
A.A. Elfeel and Ahmed A. Bakhashwain
Department of Arid Land Agriculture, Faculty of Meteorology, Environment and Arid Land
Agriculture, King Abdulaziz University, P.O. Box 80208, Jeddah 21589, Saudi Arabia
Abstract: A greenhouse experiment was conducted at the Agricultural Research Station, King Abdulaziz University
to examine the effects of salinity on biomass production, physiological responses, mineral uptake, leaves quality
(protein, fiber, ash) and tannin content. A 4 months old seedlings were exposed to an increasing salt concentrations:
(Bore well water, 7, 9 and 12 dS/m, respectively). Physiological traits Specific Leaf Area (SLA), Leaf Dry Matter
Content (LDMC) and Relative Water Content (RWC)) were measured at different growth development. Leaves
minerals (N, P, Na, Ca, K, Mg), protein, fiber and ash contents were analyzed. Condensed tannins were assayed by
vanillin HCI method. The results showed that salinity resulted in reduced biomass production and growth in
response to lower SLA, lower RWC and higher LDMC with increasing salt concentrations. The salts accumulation
in soil media resulted in higher Na associated with lower (N, P, Ca, K, Mg) contents in leaves, while tannin was
increased with increasing salt concentration. Protein, ash and fiber contents were significantly differed among salt
treatments. Despite the effects of salt stress on growth, the relatively good performance of the seedlings under all
levels of salt concentrations indicates that this species has adaptive mechanisms to withstand relatively high levels
of salinity.
Keywords: Biomass production, relative water content, salinity, specific leaf area, tannins
World due to its evergreen nature, drought tolerance,
moderate salt resistance and potential forage and wood
production (Nativ et al., 1999). Many authors
investigated the potential of A. saligna as fodder tree
species (Mahipalaa et at., 2009; Tamir and Asefa, 2009;
El-Meccawi et al., 2008; George et al., 2007; AbdelFattah, 2005; Degen et al., 1997). The tannin contents
affects its nutritive value, but the high protein contents
makes it a good sources of supplementary fodder
especially during the dry season (Degen et al., 1995).
The value of A. saligna among others exotic and
indigenous Acacias as sources of fodder in Saudi
Arabia, especially during the dry season was reported
(Al-Soqeer, 2008).
Salt stress affects various plant processes and
growth strategies, including dry matter production,
Relative Water Content (RWC), Specific Leaf Area
(SLA) and minerals uptake. SLA (leaf area per unit dry
mass) and LDMC (the ratio of leaf dry mass to fresh
mass) are among the most important traits associated
with plant growth strategy and survival (Li et al., 2005).
Also, SLA and LDMC can be used to estimate leaf
thickness (Vile et al., 2005). Leaf thickness plays an
important role in leaf and plant functioning and relates
to species strategy of resources acquisition and use.
INTRODUCTION
Salinity is common problem in arid and semi arid
regions, where rainfall is insufficient to leach excess
salt (Pessarakli and Szabolcs, 2010). The shortage of
water plus high salinity is major factors hindering plant
growth in these salty lands. The Kingdom of Saudi
Arabia (KSA) is lying entirely in arid and semi-arid dry
land, with very limited vegetation cover. More than
76% of its land area is receiving less than 100 mm
rainfall per annum and lacking other sources of
supplementary irrigation, except ground water drawn
from bore wells, which are in most cases saline (AboHassan and Tawfeeg, 2006). There is a shortage of
adequate year round feeding resources for livestock.
Drought resistance and salt tolerant fodder trees and
shrubs can provide a suitable feeding source to fill this
gap. Among potential species which receive Worldwide
attention as multi-purpose trees suitable for arid lands is
Acacia saligna. A. saligna is multi-stemmed, thorn less
and spreading shrub or single stemmed, belongs to the
family fabaceae and native to Australia (ICRAF, 2011).
The species is widely adaptable to barren slopes,
degraded lands and arid conditions (Marcar et al.,
1995). It was introduced to many countries around the
Corresponding Author: A.A. Elfeel, Department of Arid Land Agriculture, Faculty of Meteorology, Environment and Arid
Land Agriculture, King Abdulaziz University, P.O. Box 80208, Jeddah 21589, Saudi Arabia, Tel.:
+966-59505799, +966-567420763
990
Res. J. Environ. Earth Sci., 4(11): 990-995, 2012
Leaf thickness negatively affects photosynthesis and
growth rates, but in another site it helps plant survival
and longevity (Vile et al., 2005). SLA is used as index
for plant growth, due to its strong association with
relative growth rate (Wright Ian and Westoby, 2001)
and total biomass production (Tuomela et al., 2000).
RWC is an appropriate estimate of plant water status in
terms of cellular hydration under the possible effect of
both leaf water potential and osmotic adjustment
(González and González-Vilar, 2003). Salt stress
normally resulted in reduced RWC (El-Bassiouny et al.,
2005).
Currently many organizations evaluating the
genetic resources of A. saligna as multi-purpose tree on
farmland affected by dry land salinity. Marcar et al.
(1995), classified this species as moderately salt
tolerant suitable for dry land afforestation. The
introduction of this species in the dry lands of KSA
requires understanding of its growth performance and
responses under salty conditions.
Therefore, the objectives of this study was to
investigate the effects of salt stress on growth, biomass
production, minerals contents and leaves chemical
composition in relation to specific leaf area, leaf dry
matter content, relative water content and Na
accumulation.
MATERIALS AND METHODS
Experimental design: Green house experiment was
conducted in Agriculture Research Station of the King
Abdulaziz University, located in Hada Al-Sham during
the period August, 2010-April, 2011 to test the response
of A. saligna Seedlings to salinity stress. The
experiment was laid out in randomized complete blocks
design with three replicates and four factors (NaCl
concentrations). The salts concentrations are: control
(bore well water = 1.5 dS/m), 7, 9 and 12 dS/m,
respectively. The concentrations were made by mixing
of salt with water in tanks and adjusted by potable EC
Meter until the reading reach the appropriate
conductivity for each concentration. The seedlings were
grown in polythene backs (10×20 cm) when flat for
three months and then uniform seedlings were selected
and transplanted in large pot trays. The seedlings in the
pot trays were allowed to stand for one month as
recovery period, after which the four salt treatments
were applied.
Growth traits: Shoot Length (SL), Root Collar
Diameter (RCD) and Leaf Expansion (LE) were
measured at one month interval. At the end of the
experiment shoot length, root collar diameter, Shoot
Dry Weight (SDW), Root Dry (RDW) and Leaves Dry
Weight (LDW) were determined.
Specific Leaf Area (SLA) and Leaf Dry Matter
Content (LDMC): SLA was calculated as the ratio of
leaf area to leaf dry weight, while, LDMC was
estimated as the ratio of leaf dry weight to fresh weight.
For both SLA and LDMC the measurements were made
at one month interval. To measure the leaf area five
fully grown leaves were collected per seedlings for
three seedlings in each treatment and weighed. The
fresh leaves were scanned and subsequently the area
was measured using digital image analysis software
package (UTHSCSA Image Tool, version 3.0). The
leaves were then oven-dried at 65oC for 72 h and dry
weight was obtained.
Relative Water Content (RWC): For determination of
RWC freshly fully expanded leaves were cut and placed
in an airtight vial and immediately taken to the
laboratory where it was weighed. The samples were
then hydrated to full turgidity by floating the leaves on
de-ionized water in a closed Petri dish for six hours.
The samples are taken out of water and well dried of
any surface moisture quickly and lightly with filter
paper and immediately weighed to obtain fully turgid
weight. Samples were then oven dried at 80oC for 48 h
and dry weight determined. RWC was calculated using
the equation: RWC (%) = (Wf-Wd) / (Wt-Wd) ×100%,
where W (f) is the fresh weight, W (d) is the dry weight
and W (t) is the turgid weight (González and GonzálezVilar, 2003).
Mineral contents: Leaves mineral contents (Ca, Na, K
and Mg) were analyzed using Perkin Elmer model 3110
atomic absorption spectrophotometer (PERKIN
ELMER CORP, 1994), according to Hanlon (1998).
Nitrogen was analyzed by micro-kjeldah method
(Horneck and Miller, 1998), while P was determined
according the method described by Bhargava and
Raghupalhi (1993).
Protein, crude fiber and ash contents: Protein content
was determined as N content multiplied by 6.25. The
crude fiber and ash contents were determined according
to the AOAC official methods 978.10 and 945.05
(AOAC, 2006), respectively.
Determination of condensed tannin content: Tannin
content was estimated using vanillin HCI method as
described by FAO (2000).
Statistical analysis: All the data were subjected to
analysis of variance and mean separation test using
SAS Statistical Analysis Software (SAS System,
Version 8).
RESULTS
Growth traits: The whole seedlings growth and
biomass production was shown in Table 1. Total
biomass production (shoots dry weight, roots dry
weight and leaves dry weight) were significantly
991 Res. J. Environ. Earth Sci., 4(11): 990-995, 2012
Table 1: Effect of different salt concentrations on growth traits and biomass production of A. saligna seedlings
Parameters
--------------------------------------------------------------------------------------------------------------------------------------------SL (cm)
RCD (mm)
BNO
SDW (g)
RDW (g)
LDW (g)
Treatment
Control
108.8a
9.9a
7.6a
10.8a
2.8a
10.4a
7 dS/m
88.4ab
7.4b
4.1b
8.3ab
2.5a
8.3b
9 dS/m
85.3ab
7.3b
4.0b
6.6ab
2.1a
6.9b
12 dS/m
81.1b
7.1b
3.9b
6.20b
1.9a
6.9b
Treatment
*
*
***
***
ns
*
significance (p)
*: ≤0.05; **: ≤0.01; ***: ≤0.001; ns: Not significant
control
120
7
9
12
control
50
100
7
9
12
40
80
30
60
20
40
20
10
0
1st
2nd
0
3rd
1st
Fig. 1: Effect of different salt concentrations on shoot length
(cm) of A. saligna over three harvests
12
control
7
9
12
2nd
3rd
Fig. 3: Effect of different salt concentrations on leaf
expansion (leaf area cm2) of A. saligna over three
harvests
10
control
8
35
6
30
4
25
2
20
0
15
1st
2nd
3rd
7
9
12
10
5
Fig. 2: Effect of different salt concentrations on root collar
diameter (mm) of A. saligna over three harvests
reduced with increased salt concentrations. Also, shoot
length and root collar diameter were significantly
differed with increasing salt concentrations (p = 0.05).
The difference in shoot and diameter growth between
different salt concentrations was greatly increased with
time (Fig. 1 and 2). However, for root collar diameter
concentrations of 9 and 12 dS/m showed more or less
equal values (Fig. 2). Figure 3 revealed that salt stress
was highly and progressively decreased leaf expansion
with time. The effect increased with increased salt
concentration, where the control was greatly higher. All
growth traits including, shoot length, root collar
diameter and leaf expansion were remarkably and
highly different between control and other salt
concentrations in harvest three.
0
1st
2nd
3rd
Fig. 4: Effect of different salt concentrations on specific leaf
area (SLA cm2/g) of A. saligna over three harvests
Specific leaf area and leaf dry matter content: As
shown in Fig. 4 SLA decreased with increased salt
concentration. However, the general trend was an
increase in SLA in harvest two and decreased in harvest
three. In contrast to SLA, LDMC was increased with
increased salt concentration. However, in second
measurement LDMC has no significant differences
among treatments (Fig. 5).
Relative water content: Salt stress reduced RWC with
increasing salt doses. The highest RWC was observed
992 Res. J. Environ. Earth Sci., 4(11): 990-995, 2012
Table 2: Effect of different salt concentrations on mineral contents, protein, fiber and ash and tannin contents of A. saligna leaves
Parameters
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------Mg mg/L
Ca mg/L
Na mg/L
K mg/L
Treatment
N (%)
P (%)
(ppm)
(ppm)
(ppm)
(ppm)
Protein (%)
Fiber (%)
Ash (%)
Tannin (%)
186.4a
14.9a
25.72c
9.11c
0.8832b
Control
2.38a
0.212a
419.6a
531.1a
117.8d
7 dS/m
2.10b
0.210a
396.0b
342.2c
122.9c
178.4b
13.1b
28.20b
10.72a
0.9499b
2.10b
0.120b
358.9c
402.2b
136.8b
171.6
13.1b
29.12a
8.82d
1.0666a
9 dS/m
12 dS/m
2.10b
0.130b
164.5d
225.6d
141.3a
125.9d
13.1b
28.22b
9.29b
1.0999a
Treatment
*
***
***
***
***
***
*
***
***
*
significance (p)
*: ≤0.05; **: ≤0.01; ***: ≤0.001; ns: Not significant
control
7
9
12
0.3
0.25
0.2
0.15
0.1
0.05
0
1st
2nd
Fig. 5: Effect of different salt concentrations on Leaf Dry
Matter Content (LDMC gg-1) of A. saligna
94
92
90
control
7
9
12
salinity level. For N only the control was significantly
higher than other concentrations that showed no
significant differences (Table 2).
Protein, fiber and ash: The analysis of variance
revealed a high significant differences in protein, fiber
and ash contents among different salt concentrations
(p≤0.01) (Table 2). The protein content was
significantly higher in control treatment, whereas in
other salt concentrations the levels of protein content
were more or less equal. However, the overall protein
content in all concentrations was moderately high
(Table 2). The fiber was differed among salt
concentrations, with least value in control. The trend in
ash content was not consistent, though it was
significantly
differed
between
different
salt
concentrations (Table 2).
Tannin content: Tannin contents were significantly
differed according the salt concentrations applied. The
tannin content was increased with increasing salt
concentration (Table 2).
88
86
84
DISCUSSION
82
80
78
1st
2nd
Fig. 6: Effect of different salt concentrations on relative water
content (RWC %) of A. saligna
in control treatment, while the lowest in concentration
12 dS/m (Fig. 6). RWC in all treatments was increased
with increasing plant age (Fig. 6).
Minerals content: The ANOVA results showed that all
minerals analyzed in leaves were very highly differed
between salt treatments (p = 0.000) (Table 2). In regard
to Na, the salt concentration on the soil culture
significantly induced an increase Na in the leaves. The
effect was associated with the increase in high salt
doses (Table 2). The other minerals (N, P, Mg, Ca and
K) were significantly decreased in response to the
increased salt concentrations (Table 2). (P, Mg, Ca, K)
were drastically dropped from control to highest
Acacia saligna was considered as moderately salt
tolerant (Marcar et al., 1995). The present study
showed that the net effects of salt stress on A. saligna
seedlings were reduction in growth and biomass
production with increased salt concentration. Total
biomass, shoot length and root collar diameter was
significantly higher in control than other treatments.
However, root dry matter content was not significantly
different between different salt concentrations. This is
similar to Rejili et al. (2007) results in Lotus creticus.
This may be explained by the direct effects of salt stress
in aerial organs growth reduction. The reduction in
growth was in response to higher values of SLA
associated with lower doses of salts and higher values
of LDMC associated with higher doses of salts. The
higher value of SLA, which means that Less carbon
invested per unit leaf area, is proportionally related to
higher growth rate (Wright Ian and Westoby, 2001;
Beadle (1993). This explains the relationship between
SLA with growth and biomass production. Also, It was
reported that lower value of LDMC reflect in better
growth (Li et al., 2005). SLA and LDMC may be some
of these species adaptive mechanisms for survival. SLA
and LDMC were reported to be useful factors to
993 Res. J. Environ. Earth Sci., 4(11): 990-995, 2012
estimate leaf thickness, which have strong relationship
with plant growth rate and strategy to survive
(Vile et al., 2005).
Relative Water Content (RWC) was highly and
significantly higher in control treatment, whereas was
decreased with increasing salt concentrations. The
RWC was reduced due the direct effect of salt
accumulation on water potential and osmotic
adjustment (González and González-Vilar, 2003). The
reduction of RWC content as the result of salt stress
was reported by El-Bassiouny et al. (2005). The
influence of reduction of RCW with increased salt
concentration was shown by lower growth rate.
Deleterious effects of Na salinity stress may be
attributed to low water potential or ionic toxicity
(Pessarakli and Szabolcs, 2010). Our results indicate
that Na content in leaves increased with increasing
salinity. It is known that in saline soils plants take up
excessive Na at the expense of K and Ca (Alam, 2010).
The high content of Na and the low contents of K and
Ca recorded in leaves with increasing salt
concentrations may be due to the accumulation of Na in
the soil media. Also, the observed low RWC under high
salt concentrations be attributed to the effects of Na on
the osmotic potential. Similar results recorded negative
effects of Na accumulation in the soil on other nutrients
and osmotic adjustment (Belkheiri and Mulas, 2011).
The results showed that protein content in control
treatment was significantly higher, whereas there is no
significant difference among other salt concentrations.
However, the level of protein recorded in this study in
all treatment was within the range for this species
(Marcar et al., 1995). This may support the reports of
Degen et al. (1995), that A. saligna can be a good
source of supplementary feeding in dry regions. The
constituents of fiber is one of most remarkable factors
limit forage intake and digestibility (El Shaer, 2010).
The study showed an increase in tannins with
increasing salt concentration. The high levels of tannins
associated with high levels of fiber may have negative
effect in leaves quality. Many authors recorded high
levels of legnins and tannins for this species, which
affects the quality of the forage (Mahipalaa et al., 2009;
Tamir and Asefa, 2009; El-Meccawi et al., 2008). That
is why Krebs et al. (2007), concluded that A. saligna
leaves was inadequate as the sole source of nutrients
without addition of supplements.
CONCLUSION
The present study revealed that salt stress resulted
in reduced biomass production and growth. This
reduction was proportionally related to reduction in
SLA and RWC accompanied with increase in LDMC
with increasing salt concentrations. However, a good
survival of seedlings throughout the experiment
indicates that this species developed adaptive
mechanisms for salt tolerance. In addition to that, the
high levels of protein in all treatments makes it a good
source for forage feeding, but the presence of the
tannins prefers it as supplementary feed.
ACKNOWLEDGMENT
We grateful to the Faculty of Meteorology,
Environment, Arid land Agriculture-KAU for their
invaluable assistance.
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