Some Ultrastructural Observations on Endodermal Cell Development in Zea Mays Roots

Abstract

The fine structure of primary, secondary, and tertiary stages of Zea endodermal cell development was investigated. The casparian strip formed in situ in the anticlinal walls and remained at a fixed point relative to the endodermis‐pericycle boundary. The only protoplasmic structure that had a constant spatial association with the developing strip was the plasmalemma. Plasmodesmata appeared to be more numerous on the tangential walls than on radial walls; only rarely were they located in the casparian strip. The suberized lamella developed on inner and outer tangential walls before it appeared on the radial walls. No cytoplasmic organelles were found to have any particular spatial association with this layer. The suberized lamella was about 0.04 μm thick except near plasmodesmata and along the adaxial margin of the casparian strip, where it was thicker. Occasionally it failed to form along the abaxial margin of the strip. The adherent affinity between plasmalemma and casparian strip was lost after the strip was covered by suberized lamella. The secondary wall became asymmetrically thickened by differential deposition of successive lamellae. A thin layer of secondary wall material extended across the floor of each pit. Pit cavities often contained mitochondria, and plasmodesmata were restricted to the pits. The plasmodesmata were constricted where they entered the thin layer of secondary wall material and where they penetrated the suberized lamella. The various stages of cell development tended to be asynchronous. No passage cells were observed. Endodermal cell development in Zea closely resembles that described for barley.

Ion Uptake in Relation to the Development of a Root Hypodermis

“…These results allow us to consider the relative significance of suberization of the endodermis and of the outer cortical cells. The development of the endodermis under the conditions in which our maize plants were grown in the present work has been described by Ferguson and Clarkson (1975), and a more detailed account of endodermal development in Zea mays has been published recently by Haas and Carothers (1975). In the 12-cm region, where lateral roots are being initiated, and in some cases are emerging from the pericycle, suberin lamellae have been laid down in some, but not all, endodermal cells.…”

Radicular anatomy of twelve representatives of the Catasetinae subtribe (Orchidaceae: Cymbidieae)

“…These are always side roots and often adventitious (Hoehne 1949), which emerge from nodules of the rhyzoma rings. The roots of the orchids are revested by a velamen, which is responsible for the photosynthesis functions, gaseous exchanges, fixation and nutrient absorption that comes from organic and liquid substances (Hoehne 1949, Sanford and Adanlawo 1973, Haas and Carothers 1975, Benzing and Friedman 1981, Pridgeon et al 1983, Singh 1986, Oliveira and Sajo 1999. Stern and Judd (2001) described the anatomy of the vegetative organs of several Catasetinae, mainly of the Amazon region.…”

Cluster root development in Grevillea robusta (Proteaceae). II. The development of the endodermis in a determinate root and in an indeterminate, lateral root

“…Later, at 70 mm from the apex, the band expands until, at 80 mm, it fills the entire radial wall (Barnabas & Peterson, 1992). Haas & Carothers (1975) report that in Zea, Casparian band formation is at a single, precisely determined site, with no shift in position. This has also been reported for Hordeum vulgare (Robards et al, 1973).…”