TITLE:
Combined Effect of Water Deficit and Salt Stress on the Structure of Mesophyll Cells in Wheat Seedlings
AUTHORS:
Galina Semenova, Irina Fomina, Anatoly Ivanov
KEYWORDS:
Chromatin; Meso- and Ultrastructure of Mesophyll; Salt and Water Stress; Triticum aestivum
JOURNAL NAME:
CellBio,
Vol.3 No.1,
March
4,
2014
ABSTRACT: The purpose of the work was to assess the combined effect of drought and
salinity (50, 100, 200 mМ NaCl) on the meso- and ultrastructure of mesophyll
cells of wheat seedlings. Stress development was estimated by a decrease in the relative water content (RWC) and
CO2-dependent O2 evolution (An) in leaves. The decrease in the RWC and in An occurred rapidly in the absence of salt in the substrate
and slowly in the presence of salt, especially at a
treatment of 100 mM NaCl. The resumption of watering led to
the recovery of the both parameters in all variants except one with 200 mM
NaCl. Structural studies showed that a weak drought stress (RWC 60%) without
salinity led to the destruction of cell membranes and hyaloplasm, which did not
occur in all salt treatments. By contrast, the ultrastructure
of nuclei in weak drought without salinity remained unchanged, whereas in all salt treatments chromatin changed substantially.
Heterochromatin underwent a strong condensation followed by the
fusion into a united mass with the simultaneous loss of electron density. A
strong water stress (RWC 40%) in all variants led to cell destruction and the
hydrolysis of cell compounds. Under the drought without salinity, vacuoles
disappeared, whereas in salt-treated samples they were retained
and filled with organelles being at different degrees of degradation. Cell nuclei under strong drought stress lost their
rounded shape, nuclear envelopes were destroyed, and at the end only a finely
dispersed substance remained. Thus, under the combined action of drought and
salt, there is some critical level of salt concentration in substrate above which the effect of NaCl changes to the adverse, which
enhances the action of drought. Among structural components of mesophyll cells,
the most sensitive parts to NaCl are nuclei and their chromatin.