Salt excretion in Suaeda fruticosa.
ABSTRACT Suaeda fruticosa is a perennial "includer" halophyte devoid of glands or trichomes with a strong ability of accumulating and sequestrating Na(+) and Cl(-). We were interested in determining whether leaf cuticle salt excretion could be involved as a further mechanism in salt response of this species after long-term treatment with high salinity levels. Seedlings had been treated for three months with seawater (SW) diluted with tap water (0, 25, 50 and 75% SW). Leaf scanning electron microscopy revealed a convex adaxial side sculpture and a higher accumulation of saline crystals at the lamina margin, with a large variability on repartition and size between treatments. No salt gland or salt bladder was found. Threedimensional wax decorations were the only structures found on leaf surface. Washing the leaf surface with water indicated that sodium and chloride predominated in excreted salts, and that potassium was poorly represented. Optimal growth of whole plant was recorded at 25% SW, correlating with maximum Na(+) and Cl(-) absolute secretion rate. The leaves of plants treated with SW retained more water than those of plants treated with tap water due to lower solute potential, especially at 25% SW. Analysis of compatible solute, such as proline, total soluble carbohydrates and glycinebetaine disclosed strong relationship between glycinebetaine and osmotic potential (r = 0.92) suggesting that tissue hydration was partly maintained by glycinebetaine accumulation. Thus in S. fruticosa , increased solute accumulation associated with water retention, and steady intracellular ion homeostasis confirms the "includer" strategy of salt tolerance previously demonstrated. However, salt excretion at leaf surface also participated in conferring to this species a capacity in high salinity tolerance.
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ABSTRACT: During the last 20 years, a wealth of data dealing with scanning electron microscopy of plant surfaces has been published. The ultrastructure of epidermal surfaces has been investigated with respect to taxonomic, as well as functional aspects. Within the latter, water-repellency has received much attention and has been well documented. Water-repellency is based on surface roughness caused by different microstructures (trichomes, cuticular folds and wax crystals), together with the hydrophobic properties of the epicuticular wax. In addition, contaminating particles are carried away by water droplets, resulting in a cleaned surface (Lotus-effect). Therefore, rough, waxy leaves are not only water-repellent but anti-adhesive with respect to particulate contamination. Based on 200 water-repellent plant species, the present paper surveys micromorphological characteristics of anti-adhesive plant surfaces. Leaves that are permanently water-repellent can be differentiated by distictively convex to papillose epidermal cells and a very dense layer of epicuticular waxes. Leaves that are water-repellent for only a limited period of time have only slightly convex epidermal cells and often have a less dense wax layer. Finally, an overview is given on the occurrence of water-repellency among different life forms and within different habitats. Water-repellency is concentrated in herbaceous species, while it is rare in trees. Among different habitats, subtropical regions, wetlands and disturbed areas appear to have more species with water-repellent leaves. The importance of roughness and water-repellency, respectively, as the basis of an anti-adhesive, self-cleaning surface, in comparison to other functions of microstructures, is discussed.01/1997;
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ABSTRACT: Plant cuticles are lipid membranes with separate diffusion paths for lipophilic non-electrolytes and hydrated ionic compounds. Ions are lipid insoluble and require an aqueous pathway across cuticles. Based on experimental data, the aqueous pathway in cuticles has been characterized. Aqueous pores arise by hydration of permanent dipoles and ionic functional groups. They can be localized using ionic fluorescent dyes, silver nitrate, and mercuric chloride. Aqueous pores preferentially occur in cuticular ledges, at the base of trichomes, and in cuticles over anticlinal walls. Average pore radii ranged from 0.45 to 1.18 nm. Penetration of ions was a first order process as the fraction of the salt remaining on the cuticle surface decreased exponentially with time. Permeability of cuticles to ions depended on humidity and was highest at 100% humidity. Wetting agents increased rate constants by factors of up to 12, which indicates that the pore openings are surrounded by waxes. The pores in cuticular ledges of Helxine soleirolii allowed passage of berberine sulphate, which has a molecular weight of 769 g mol(-1). Increasing the molecular weight of solutes from 100 to 500 g mol(-1) decreased the rate constants of penetration by factors of 7 (Vicia faba) and 13 (Populus canescens), respectively. Half-times of penetration of inorganic salts and organic ions across Populus cuticles and Vicia leaf surfaces varied between 1 and 12 h. This shows that penetration of ionic compounds can be fairly rapid, and ions with molecular weights of up to 800 g mol(-1) can penetrate cuticles that possess aqueous pores.Journal of Experimental Botany 02/2006; 57(11):2471-91. · 5.24 Impact Factor
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ABSTRACT: The purpose of this study was to examine the hypoglycemic activity of the aqueous extract of the aerial part of Suaeda fruticosa (SF) in normal and streptozotocin-induced diabetic rats. The aqueous extract was administered intravenously (i.v.) and the blood glucose changes were determined within 4 h after starting the treatment. Plasma insulin, cholesterol and triglycerides levels were also determined. The aqueous extract at a dose of 192 mg/kg produced a significant decrease in blood glucose levels in normal rats (P < 0.05), and even more in diabetic rats (P < 0.001). This hypoglycemic effect might be due to an extra-pancreatic action of the aqueous extract of SF, since that the levels of plasma insulin were unchanged between the values before and after treatment. In the other hand, the effect of the aqueous extract on the plasma cholesterol were also significant in both normal and diabetic rats (P < 0.05). But, there is no significant effect of SF on plasma triglycerides in both groups. In order to characterize the active principle(s), which could be responsible for the therapeutic effect, preliminary phytochemical analysis of the aqueous extract of the plant has been investigated.Journal of Ethnopharmacology 06/2001; 76(1):35-8. · 2.76 Impact Factor