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International Journal of Horticulture 2014, Vol.4, No.13, 64
-
71
http://ijh.biopublisher.ca
65
growth reduction (Sykes and Wilson, 1988; Tominag
and Ueki, 1991). Salt spray has been widely reported
to reduce growth in many coastal plants (Cheplick and
Demetri, 1999; Morant-Manceau et al., 2004;
Scheiber et al., 2008). However, species growing in
the vicinity of the tide line have adapted to salt spray
in various ways (Rozema et al., 1985; De Vos et al.,
2010). For example, increased succulence in the
presence of salt is an adaptive mechanism for ion
dilution (Debez et al., 2004). Salt spray disrupts plant
water balance (Munns, 1993; Touchette et al., 2009)
but tolerant plants can adjust osmotically to water
stress through reduction in water potential (Griffiths &
Orians, 2003; Griffiths, 2006; Touchette et al., 2009).
Griffiths & Orians (2003) reported that
Myrica
pensylvanica
showed high resistance to necrotic
damage caused by salt spray and attributed it to thick
cuticle on leaf surface that limits salt entry. Reduction
in leaf area brings about a decrease in the surface
available for salt deposition and water loss through
transpiration, which are strategies to cope with water
stress (Morant-Manceau et al., 2004).
Landscaping and gardening projects in coastal regions
have called for selection of plants that have the ability
to cope with seawater sprays, considering the high
level of the death of sea side horticultural plants
(Scheiber et al., 2008; Conolly et al., 2010). However,
landscape value is largely determined by the physical
appearance of individual plants, and plants showing
significant necrotic damage due to salt stress are
inherently of less value than plants without such
damage, regardless of the concentration of ions
causing the necrosis (Conolly et al., 2010). With this
in mind, a pot experiment was conducted in 2013 to
investigate tolerance of seashore paspalum to sea
spray at Adekunle Ajasin Univbersity, Akungba Akoko,
Ondo State Nigeria (Lat. 7
0
N 28
1
, Long. 5
0
44
1
E). The
objectives of this research are to (1) quantitavely
determine the growth of seashore paspalum under sea
water spray treatments, to have an insight in the
ecophysiological adaptations underlying the responses
and (2) to determine if the quality of seashore paspalum
sprayed at different levels with seawater would be
affected. This will provide researchers and end users with
basic information regarding how tolerant
P. vaginatum
is
to sea sprays and the underlying adaptive fissures.
1 Results
The morphological change observed in the plants
under salt sprays was folding of leaves. All plants
survived under salt spray but growth was inhibited
(Table 1). With the exception of stem girth that
increased under sea spray relative to the control, other
growth parameters decreased with increase in salt
spray level. Leaf width, root number and root length
were however not affected by sea spray.
Table 1 Percentage survival and some growth parameters of
Paspalum vaginatum
after 12 weeks of exposure to different levels of
salt spray
Level
of salt
spray
Survival
(%)
Stem
girth
(cm)
Number
of leaves
plant
-1
Number of
branches
plant
-1
Shoot
length
(cm)
Number
of nodes
plant
-1
Internode
length
(cm)
Leaf
length
(cm)
Leaf
width
(cm)
Leaf
area
(cm
2
)
Root
length
(cm)
Number
of Roots
plant
-1
CSS 100.00
1.71
a
48.25
a
8.50
a
66.78
a
13.00
a
4.13
a
19.63
a
0.58
a
33.34
a
25.04
a
14.04
a
2SS
100.00
2.46
b
31.50
b
6.25
a
54.26
b
8.50
ab
2.58
b
19.43
a
0.48
b
20.23
b
23.20
a
16.20
a
4SS
100.00
2.52
b
13.75
b
3.00
b
45.10
b
9.75
b
2.78
b
17.83
a
0.47
b
16.41
b
17.14
a
13.14
a
6SS
100.00
2.23
b
9.75
b
2.25
b
25.67
b
8.50
b
2.70
b
7.78
b
0.48
b
16.24
b
18.39
a
13.75
a
Note: Each value is a mean of 6 replicates; For each parameter, means with the same letter(s) in superscript in the same column are
not significantly different at P≥0.05 (Tukey HSD); CSS=deionized water sprays (control), 2SS=two salt sprays per week, 4SS = four
salt sprays per week, 6SS=six salt sprays per week
Stems, leaves and shoot fresh mass decreased
significantly in seawater-sprayed plants compared to
the control (Table 2). Root fresh and dry mass values
in plants under salt spray did not differ significantly
from that of control. Total biomass, relative growth
rate and leaf total chlorophyll (LTC) in plants exposed
to salt spray were significantly lower than in plants
sprayed with de-ionized water (Table 2).
Sea sprays induced leaf and stem succulence in the
test plant (Table 3). When compared to the control,
percentage moisture content increase was not significant
for leaf but for stem while air-borne salt did not affect
root moisture content. Plant xylem water potential was