Molecular Soil Biology 2015, Vol.6, No.2, 1-6
2
sungkianica
seeds are on the declining curve as the
concentration of NaCl rise, due to the stress effects
(Table 1). A low concentration of NaCl suppress seed
germination. The germination rate was 55.50±2.81%
when NaCl=50 mmol/L, far lower than the control
group (0 mmol/L, 77.00±2.12%) (P<0.01), the same
with other indicators. And, germination happened on
the second day when NaCl≤200 mmol/L; the third day
when NaCl=250 mmol/L at a rate of 7.00±0.12%, with
no growth of radicle though the cotyledon were
unfolded. It is thus clear that the present of NaCl will
significantly postpone seed germination and suppress
the growth of sapling. Linear regression analysis was
adopted to analyze the different NaCl concentrations
and relative germination rates. The linear regression
equation is
y
=
-
0.319
x
+94.174,
R
2
=0.974. The salt-tol-
erance limit, semi-lethal salt concentration, and salt
concentration of
S. sungkianica
seeds are 216.84,
138.47, and 60.11 mmol/L, respectively. Most seeds
treated with NaCl had gone dark-brown. In the
re-germination test, those which color had changed
showed no sign of re-germination while the unchanged
ones did. And the re-germination rate dropped as the
concentration rose. Therefore a deduction can be
made that the stress effects of NaCl could be the
combination of infiltration effect and ion effect (Andre
et al., 2014; Zeng et al., 2006).
Table 1 Effect of NaCl on the growth of the seedlings of
S.sungkianica
Item
Concentration of NaCl (mmol/L)
0
50
100
150
200
250
Germination percentage (%)
77.00±2.12a
55.50±2.81b
38.50±1.01c
31.00±0.45d
23.00±0.41e
7.00±0.12f
Seeding length(mm)
5.03±0.34a
3.84±0.21b
3.11±0.29c
2.64±0.18d
2.52±0.16e
2.32±0.12e
Germination potential (%)
74.50±2.08a
49.80±1.84b
36.50±0.72c
29.00±0.46d
20.50±0.38e
0.00±0.00f
Germination index
56.50±4.02a
38.63±2.71b
19.93±1.21c
12.33±0.87d
8.00±0.78e
5.25±0.64f
Vigor index
79.66±5.99a
45.19±5.52b
16.34±1.02c
7.76±0.81d
2.78±0.280e 0.39±0.02f
1.1.2 Influence of NaCl upon anatomical structure
of
S. sungkianica
root
Root plays a significant role in the vegetation process
of plants. When the environmental condition becomes
worse, the external form and internal structure would
be modified to accommodate the change (Wang et al.,
1997). Figure 1-A shows the anatomical structure of
S.
sungkianica
root. From out to core, the cross section is
divided by epidermis, cortex and vascular bundle. The
cortex contains exodermis, cortex, parenchymatous
tissue and endodermis. The exodermis contains one or
two layers of tightly aligned parenchymal cell. When
the epidermis is destroyed, the exodermis become
the defensive tissue, then the cortex and so on.
Parenchymal cell is small and less regular shaped,
some of them go rupture and becomes the aerenchyma,
which is a peculiar structure of hydrophyte and
hygrophyte. The
S. sungkianica
, which always grow
along the river or in wetland, also process the
aerenchyma. In recent years, research on halophyte
has gaining some progress. Plants grow on saline-alkali
land have difficulty in obtaining oxygen from the
hardening soil, which also happens on hydrophyte and
hygrophyte. To counter this adversity, the parenchymal
cell go rupture, or separate from middle lamella, and
the intercellular space among the biggish cell becomes
connected, thus a clear aerenchyma comes into shape
which ensures a normal respiratory metabolism
(Werner et al., 1990; Wang, 2008). Therefore the
S.
sungkianica
process a degree of salt-resistance.
Endodermis contains several layers of small
parenchymal cells. Vascular bundle includes primary
xylem and primary phloem. When NaCl=50 mmon/L
(Figure 1B), no significant difference is observed
compare with the control group, the root maintains it's
structure integrity with no obvious injury, only the
endodermis has the tendency to intensified. Hence the
S. sungkianica
illustrates a strong salt-resistance when
the concentration of NaCl is below 50 mmol/L. When
NaCl=100 mmon/L (Figure 1C), the epidermis and
exodermis vanished and the parenchymal cell of the
cortex becomes the protective tissue. Together with
the disappear of aerenchyma, a intensification of
endodermis through the thickening of radial wall and
inner-tangential wall of endodermis cells. Since the
mould solute is absorbed by the root and transformed
