Combined Effect of Water Deficit and Salt Stress on the Structure of Mesophyll Cells in Wheat Seedlings

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 CO 2-dependent O 2 evolution (A n) in leaves. The decrease in the RWC and in A n 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.

Foliar application of selenium for protection against the first stages of mycotoxin infection of crop plant leaves

“…Differences in the infrared images of temperature changes in the leaves of the various genotypes studied were caused by differences in intensity of transpiration/evaporation and by structural variations in mesophyll cells that affect the incorporation of aqueous toxin solution. The specific ultrastructure of mesophyll cells of oat, barley, and wheat has been described previously, [23][24][25] membrane permeability. 26 In additional experiments, electrolyte leakage was measured for the intact leaf surfaces of control plants using a conductometer (Elmetron, Poland), and the results related to leaf area.…”

Mechanisms of Sodium Transport in Plants—Progresses and Challenges

“…On the other hand, salt-sensitive varieties are unable to sequester salt in vacuoles and the salt accumulates rapidly in the cytoplasm followed by a reduction of photosynthesis and assimilation [ 2 , 11 ]. Salt stress causes various physiological changes such as: (1) decrease in the rate of photosynthesis [ 2 , 12 , 13 , 14 , 15 ]; (2) smaller stomatal aperture and lower stomatal conductance due to disturbed water relations and sensitivity to abscisic acid (ABA) [ 2 , 12 , 13 , 15 , 16 , 17 ]; (3) decrease in transpiration rate [ 12 , 18 , 19 ]; (4) decrease in chlorophyll a and b, total chlorophyll, and carotenoids concentrations [ 14 , 17 , 20 , 21 , 22 , 23 ]; (5) decrease in chlorophyll fluorescence [ 15 , 24 , 25 , 26 ]; (6) changes in leaf anatomy, such as a decrease in the thickness of the epidermis and mesophyll and a decrease in intercellular spaces in the leaves [ 27 , 28 ], and a reduction in root length density [ 29 , 30 ]; (7) nutrient imbalance with a decrease in the content of phosphorus, nitrogen, Ca 2+ , Mg 2+ , and K + [ 21 , 31 ]; (8) decrease in leaf relative water content [ 8 , 32 , 33 , 34 , 35 ]; (9) membrane instability and increase in membrane permeability [ 35 , 36 , 37 , 38 ].…”

Cell and chloroplast anatomical features are poorly estimated from 2D cross‐sections

“…Leaf anatomy is commonly studied in two dimensions by either light microscopy (Carriquí et al , ; Théroux‐Rancourt & Gilbert ), for tissue structure and chloroplast size and position, or transmission electron microscopy (TEM) (Semenova et al , ; Babenko et al , ), for detailed subcellular structure such as cell wall thickness. Serial block face scanning electron microscopy (SBF‐SEM) incorporates an automated ultramicrotome within the SEM specimen chamber, collecting 2D images sequentially and allowing 3D image reconstruction.…”