Maintenance of Low Cl⁻ Concentrations in Mesophyll Cells of Leaf Blades of Barley Seedlings Exposed to Salt Stress

Abstract

The concentrations of vacuolar Na+ and Cl-in the epidermal and mesophyll cells of the leaf blade and sheath of Hordeum vulgare seedlings (cv California Mariout and Clipper) were measured by means of quantitative electron probe x-ray microanalysis. A preferential accumulation of Cl-in vacuoles of epidermial cells in both blade and sheath and a low level in mesophyll cells of the blade were evident in plants grown in full strength Johnson solution. The concentration of Cl-in the mesophyll cells of the blade remained at a low level after exposure to 50 or 100 millimolar NaCI for I day or to 50 millimolar for 4 days, while at the same time the concentration of Cl-in the epidermis and mesophyll of the sheath showed a dramatic increase. Clipper generally contained more Clr in the mesophyll cells of the blade than Califomia Mariout. A greater accumulation of Na in the mesophyll of the sheath relative to that of the blade was only apparent after treatment with 100 millimolar NaCI for 1 day or 50 millimolar for 4 days. These results confirm the suggestion that sheath tissue is capable of accumulating excess Cl-(and to a lesser extent Nat) and suggest that the site of regulation of Cl-concentration in the barley leaf is located in the mesophyll cells of the blade.

Photosynthetic capacity is related to the cellular and subcellular partitioning of Na+, K+ and Cl‐ in salt‐affected barley and durum wheat

“…− to epidermal cells in both durum wheat and barley, particularly at low leaf Cl − concentrations (50-150 mM), is consistent with the findings of other studies using salt-stressed barley (Huang & van Steveninck 1989;Leigh & Storey 1993;Fricke et al 1996). This reproducible pattern of epidermal Cl − deposition has also been established in non-saline conditions (Huang & van Steveninck 1989;Fricke et al 1996), and additionally, Karley et al (2000a) found significant Cl − partitioning in the isolated epidermal protoplasts of young barley leaves in control conditions.…”

“…This reproducible pattern of epidermal Cl − deposition has also been established in non-saline conditions (Huang & van Steveninck 1989;Fricke et al 1996), and additionally, Karley et al (2000a) found significant Cl − partitioning in the isolated epidermal protoplasts of young barley leaves in control conditions. Leigh & Tomos (1993) concluded that the distribution of Cl − into the epidermis was a likely result of preferential Cl − movement through the vein extension apoplast.…”

“…However, Franklin appeared to have a greater capacity for storage of Na + in mesophyll cells, partitioning slightly greater Na + (∼ 10%) to the mesophyll compared to Wollaroi. Also using X-ray microanalysis, Huang & van Steveninck (1989) found similar concentrations of Na + in the epidermis and mesophyll of two barley cultivars (differing in salt tolerance) grown for 1 d in 50 and 100 mM NaCl, but twice the Na + in the mesophyll of both genotypes after 4 d in 50 mM NaCl. Similarly, using the same technique, Leigh & Storey (1993) encountered more mesophyll than epidermal cells with detectable levels of Na + .…”

“…Patterns of cellular ion accumulation have been characterized in salt-affected barley leaves in a number of studies using a variety of analytical techniques, including X-ray microanalysis (e.g. Huang & van Steveninck 1989;Leigh & Storey 1993), vacuolar sap extraction (e.g. Fricke, Leigh & Tomos 1996) and isolated protoplasts (e.g.…”

Concentrations of inorganic and organic solutes in extracts from individual epidermal, mesophyll and bundle-sheath cells of barley leaves

“…However, it is now becoming clear that solutes are also differentially distributed between different cell types in leaves and that these intercellular solute distributions may also respond to changes in nutrient availability (see review by Leigh and Tomos 1993). For instance, studies of barley leaves using either protoplast isolation (Dietz et al 1992b) or energy-dispersive X-ray (EDX) microanalysis of bulk-frozen hydrated sections (Leigh et al 1986;Huang and van Steveninck 1989;Williams et al 1991;Leigh and Storey 1993) have shown that P is largely restricted to mesophyll cells and is virtually indetectable in epidermal cells while the reverse is true for Ca. Other solutes such as K or Na are more-evenly distributed between the two cell types.…”