Ultrastructural features of the salt gland of Tamarix aphylla L.

Abstract

The salt gland in Tamarix is a complex of eight cells composed of two inner, vacuolate, collecting cells and six outer, densely cytoplasmic, secretory cells. The secretory cells are completely enclosed by a cuticular layer except along part of the walls between the collecting cells and the inner secretory cell. This non-cuticularized wall region is termed the transfusion are (RUHLAND, 1915) and numerous plasmodesmata connect the inner secretory cells with the collecting cells in this area. Plasmodesmata also connect the collecting cells with the adjacent mesophyll cells.There are numerous mitochondria in the secretory cells and in different glands they show wide variation in form. In some glands wall protuberances extend into the secretory cells forming a labyrinth-like structure; however, in other glands the protuberances are not extensively developed. Numerous small vacuoles are found in some glands and these generally are distributed around the periphery of the secretory cells in association with the wall protuberances. Further, an unusual structure or interfacial apparatus is located along the anticlinal walls of the inner secretory cells. The general structure of the gland including the cuticular encasement, connecting plasmodesmata, interfacial apparatus, and variations in mitochondria, vacuoles, and wall structures are discussed in relation to general glandular function.

Vesicle-Mediated Solute Transport between the Vacuole and the Plasma Membrane

“…1) in agreement with a vesicle-mediated secretion process. Comparable observations were concurrently made by Thomson and Liu (1967) in their studies of the salt-secreting gland cells of Tamarix aphylla (Fig. 2) and later by Cardale and Field (1971) and Shimony et al (1973) for salt glands of the mangrove species Aegiceras corniculatum and Avicenia marina, respectively.…”

“…During salt secretion in T. aphylla, numerous "microvacuoles" (similar to those of L. vulgare) appear at the periphery of the secreting cells and often in close association with wall projections ( Fig. 2A; Thomson and Liu, 1967). At higher magnification, direct contact between the tonoplast and the plasmalemma was also noted (Fig.…”

“…For example, secretory "gland cell complexes" are completely enclosed by an impermeable cuticular envelope opening sporadically to the underlying cells to allow symplastic connections. Across these "transfusion areas" (Thomson and Liu, 1967) the secretory cells make contact with the surrounding mesophyll through abundant plasmodesmata (Thomson and Platt-Aloia, 1985). Compartmental analysis confirmed symplastic movement of ions from the mesophyll and into the gland cells (Hill, 1970).…”

Growth and N2fixation in mixed cropping ofMedicago arboreaandAtriplex halimusgrown on a salt-affected soil using a15N tracer technique

“…As in most species within the genus Atriplex, A. halimus is a facultative halophyte that achieves salt tolerance by accumulating ions against a concentration gradient, and then parting those ions in specific cells. Salt glands, an anatomically distinct group of cells, concentrate the salt and then secrete salt crystals to the outside of the leaf surface (Thomson and Liu 1967;Qureshi and BarrettLennard 1998). This property is important because it can be proposed that one of the benefits of halophytic shrubs may be to decrease the concentration of salt in the saline soils, thereby enabling such soil to grow other plant species.…”

THE FINE STRUCTURE OF WALL MODIFICATIONS AND ASSOCIATED STRUCTURES IN CALLUS TISSUE OF ANDROGRAPHIS PANICULATA NEES.

“…These extensions of the cell wall, which are not associated with mitosis, divide the cell into progressively smaller compartments. Several authors have described the development of wall invaginations in cells associated with secretory processes (Gunning, Pate and Briarty, 1968;Maier, 1967;Schnepf, 1964;Thomson and Liu, 1967). It seems possible that the anomalous wall development in Andrographis callus is also related to a secretory process and it is interesting to note that these cultures apparently secrete paniculide B (a sesquiterpene) in relatively large amounts into the agar medium (Butcher, personal communication).…”