Ultrastructure of the salt glands of the mangrove, Avicennia marina (Forssk.) Vierh., as indicated by the use of selective membrane staining

Abstract

Each salt-excreting gland of the mangrove Avicennia marina (Forsskål) Vierh. consists of two to four collecting cells, one stalk cell, and eight to twelve excretory cells. Differential membrane staining by zinc iodide-osmium tetroxide (as a post-fixative) or phosphotungstic acid (as a section-stain) was used to characterise the ultrastructure of the glands. A large amount of tubular endoplasmic reticulum was found in the stalk and excretory cells of the gland, but not in the collecting cells. The ultrastructural arrangement of the endoplasmic reticulum indicates that salt is loaded from the apoplasm into the endoplasmic reticulum of the symplasm at the base of the stalk cell, traverses both cell types in the endoplasmic reticulum, and is excreted at the outer edge of the gland by an eccrine-type mechanism. Increasing development of the tubular endoplasmic reticulum accompanied differentiation of the gland cells.

A simple, rapid method to isolate salt glands for three-dimensional visualization, fluorescence imaging and cytological studies

“…The location of the nuclei, for example, as revealed by optical sections of isolated salt glands stained with the nuclear stain PI, was mostly found in the middle of the secretory cells (Figure 9). Large nucleus was also reported to be located predominantly in the central region of each secretory cell in Avicennia marina [7]. The positions of the nuclei observed herein were also similar to the green, spherical, autofluorescent structures noted in the middle of the secretory cells of these salt glands (Figures 4 and 5).…”

“…Each nucleus was found to be approximately 4-6 μm in diameter (Figures 9 and 10A). Relatively large nuclei of the secretory cells were also observed in other Avicennia species and in the salt glands of other genera [1,2,5,7,16,17]. Information on the correlation between the activity of salt gland nuclei and the activity of the salt glands, however, is lacking, even though larger nucleoli were reported in the secreting salt glands of Limonium platyphyllum in comparison to those without salt challenge [22].…”

Making Plants Break a Sweat: the Structure, Function, and Evolution of Plant Salt Glands

“…The Type 2 multicellular salt glands of asterids ( Figure 1 ), which are distributed among five families ( Figure 2 ; Table 1 ), tend to have one or two stalk cells connecting the secretory cells to the basal collecting cells contrasting the structure of the Tamarix-type salt glands (Shimony et al, 1973; Drennan et al, 1987; Das, 2002). While maintaining the overall similarity of the structure with a cuticular envelope covering the salt gland, the number of secretory cells compared to the number of collecting cells varies between species in the asterids.…”

“…For example, Aegiceras corniculatum and Glaux maritima (Primulaceae) have salt glands consisting of 8–40 radially arranged secretory cells atop a single basal cell (Cardale and Field, 1971; Rozema et al, 1977) while the mangroves, Avicennia and Acanthus spp. (Acanthaceae), have salt glands consisting of two to four collecting cells connected by one or two stalk cells to eight to twelve radially arranged secretory cells (Shimony et al, 1973; Drennan et al, 1987; Das, 2002). Similar to Tamarix , the cuticle of the secretory cells contains pores through which the saline solution is secreted; the secretory cells are cytoplasmically dense and rich in mitochondria and endomembranes, and the basal cell is highly vacuolated.…”

Analytical electron microscopical investigations on the apoplastic pathways of lanthanum transport in barley roots

“…Such properties in combination with its high atomic mass (z = 57) allow lanthanum to be used in transmission electron microscopy (TEM) studies as an electron-opaque tracer to delineate apoplastic pathways. Initially, the ultrastructural tracing of lanthanum was applied to animal tissues (Revel and Karnovsky 1967) and subsequently also to plants for probing apoplastic ion diusion (Thomson et al 1973;Robards and Robb 1974;Hall et al 1977;Maier-Maercker 1980;Drennan et al 1987). Because of its high anity to calcium-binding sites (Hanzely and Harmet 1982;Picton and Steer 1985) lanthanum has also been used as a tracer for calcium (Kramer and Lehmann 1986;Lehmann et al 1990;Moysset et al 1994;Apitius and Lehmann 1995).…”