Intercellular pectic strands in parenchyma: studies of plant cell walls by scanning electron microscopy.

Abstract

Rows of pectic strands, each 0.3-0.4�m in diameter, are shown to connect palisade mesophyll cells in regular ladder-like configurations ('pectic scala'). These structures are illustrated in some species of eucalypts, but probably occur in other kinds of plants. Less regular wall filaments can be observed in the intercellular spaces between other types of cells. They are particularly numerous in the parenchyma of species of ferns. These filaments and the pectic scala are readily observable by scanning electron microscopy, but can also be seen in conventional preparations for the light microscope. The structure, formation, chemical composition and possible function of these and other kinds of cell wall protuberances, described in the literature, are discussed.

Occurrence of xyloglucan containing protuberances in the storage cell walls of cotyledons of Hymenaea courbaril L.

“…They were first reported in the 19 th century (see Potgieter & van Wyk 1992 for a review), but their composition has not been defined exactly yet. Although a pectic composition has been proposed by some authors (Carr & Carr 1975, Carr et al 1980aand b, Machado & Sajo 1996, a complex composition has been proposed by others (Butterfield et al 1981). Being part of the plant cell wall, it is reasonable to suppose that different cell wall polysaccharides might be present.…”

Ultrastructure of the intercellular protuberances in leaves of Paepalanthus superbus Ruhl. (Eriocaulaceae)

“…These broken plasmodesmata were interpreted by the author as a result of the middle lamella separation during the projection development. Our observations indicate that intercellular protuberances in P. superbus are formed by secretion of materials through plasmodesmata after the development of intercellular spaces, according to Schenck hypothesis (see Carr & Carr 1975).…”

“…Intercellular pectin protuberances of varying morphological patterns are of widespread occurrence in different taxa and plant tissues (Carlquist 1956, Carr & Carr 1975, Parameswaran 1976, Heide-Jrgensen 1978, Potgieter & van Wyk 1992, Machado & Sajo 1996. Although certain morphological aspects of the intercellular projections on mesophyll cell walls are relatively well documented (Potgieter & van Wyk 1992), there are controversies over the cell wall protuberances concerning their origin, chemical composition, and biological functions.…”

“…Although certain morphological aspects of the intercellular projections on mesophyll cell walls are relatively well documented (Potgieter & van Wyk 1992), there are controversies over the cell wall protuberances concerning their origin, chemical composition, and biological functions. Some authors believe that these structures are produced only as a mechanical consequence of intercellular space development, with no obvious function (Parameswaran 1976, Carr & Carr 1975, Heide-Jrgensen 1978. Others believe that they are formed by secretion through submicroscopic "wall pores" after the formation of the intercellular spaces (Carr & Carr 1975).…”

“…Some authors believe that these structures are produced only as a mechanical consequence of intercellular space development, with no obvious function (Parameswaran 1976, Carr & Carr 1975, Heide-Jrgensen 1978. Others believe that they are formed by secretion through submicroscopic "wall pores" after the formation of the intercellular spaces (Carr & Carr 1975). Progress have been made on the ultrastructural and chemical aspects of the protuberances that develop on the surfaces of the callus cells (Davies & Lewis 1981) and on embryoid cell surfaces (Dubois et al 1991, Verdus et al 1993.…”