Environmental Engineering Reference
In-Depth Information
4.2. NaCl Stress Enormously Promoted the Accumulation of Proline
and Glycine Betain
When subjected to salinity, plants will have to take a series of necessary measures. On
the one hand, the plant would lessen stomatal conductance and cut down transpiration to
adjust to the osmotic stress, on the other hand, the plants would accumulate a great deal of
compatible solutes to lower water potential and reduce water desorption. The proline and
glycine betain were the two most effective compatible solutes, playing important protective
functions in abiotic stress (Ashraf and Foolad, 2007). Thus we chose to survey their behaviors
to reveal resistance of the soybean. Our results suggested that the contents of proline and
glycine betain were almost the same under normal conditions, but the existence of the NaCl
led to the variations and differences.
For young seedlings the accumulation of proline ascended rapidly when the concentration
of the NaCl attained 100 mM or higher. Under 300 mM, the contents of the proline reached
34.4 and 38.2 times respectively compared the control in cultivated and wild soybean. For
mature seedlings the accumulations were 24.9 and 151.1 respectively (Figure 3.2 A),
indicating that the adjustment capacity of the wild soybean was more extensive. This may
also partially explain the relative higher water potential of the wild soybean under salt stress.
Previous studies especially the researches on the synthesis and degradation of the proline
have proved the close relationship between proline and salt resistance, and our result was
unanimous (Huang et al., 2013; Kumar et al.,2010; Silva-Ortega et al., 2008; Vendruscolo et
al., 2007; Wang, 2011; Yamchi et al., 2007).
Glycine betain was another important metabolites playing important role in salt
resistance. Our research revealed that the manifestation of the glycine betain was similar to
proline (Figure 3.2A, B). The content of the glycine betain in mature seedlings of wild
soybean achieved as much as twice comparatively (Figure 3.2B), thus the accumulation of
glycine betain testified the better resistance of the wild soybean, too. Moreover, there were
many other compatible solutes such as sugars, sugar alcohols, quaternary amino acid
derivatives, sulfonium compounds and so on which were also demonstrated to participate in
the osmotic stress and play important roles. We may certify the superiority of the wild
soybean further by observing and analyzing their behaviors.
4.3. The Contents of Na
+
and Cl
-
Ascended and the Content of K
+
Descended
with Increasing Salt Concentration and the Tendency Was More Pronounced
in the Cultivated Soybean
Due to the high concentration ions in soil enclosing the roots, the plants took in and
accumulated a great deal of ions in cells unavoidable. Once the ions in the cells exceeding a
certain amount, the homeostasis of intracellular ion concentrations was disturbed and ionic
stress emerged. Now, the ions exclusion from cells and compartmentation into vacuole were
the key protective strategy adopted by plants (Agarwal et al., 2012). Na
+
and Cl
-
were of
course the main toxic ions under salinity. K
+
was proved to take part in enzymatic reactions,
protein synthesis and ribosome functions, and moreover Na
+
could act as an antagonist in
absorption and transportation of K
+
(Zhu, 2003). Thus we discussed the changes of the
