Über die Differenzierungsvorgänge in der Cruciferenwurzel

Abstract

Einleitung.Die vorliegende Untersuchung ging vonder Absicht aus, einen Einbliek in die Ursachen der Gewebedifferenzierung in der Wurzel zu gewinnen. Und zwar sollte urspriinglich vor allem die Differenzierung der Rhizodermis in Triehoblasten und gew6hnliehe Epidermiszellen gekli~rt werden. Zwangsli~ufig wurde dabei die Aufmerksamkeit auch auf die Differenzierung in den iibrigen Wurzelgeweben gelenkt. Dabei wurden wieder die Probleme der Bildung des Gefi~l~strahlenmusters lebendig, die schon JOST aufgeworfen hat. Zur Untersuchung dienten Wurzeln yon Lepidium sativum und Sinapis alba.Die S~men keimten auf •iltrierpapier, das schraggestellte Glasplatten in Glasktivetten bedeckte. Die Anzucht erfolgte im Thermostaten bei 25 ~ Zur Anfertigung der Mikrotqmschnitte wurde mit ZENKERS Gemisch fixiert und mit Hgmatoxylin nach DELAFIELD gef~rbt. Die Bildung der Gef~iBstrahlen.Die Untersuchung tier ~/nap/8-Wurzel ergab folgende Resultate: Die Zellen der zentralen Pleromreihe kSnnen sich, wie erw~hnt, durch Querw~Lude teflen. Sie teilen sich regelmii$ig auch durch L~ngsw~nde, die aber wenigstens bevorzugt immer in:ein und derselben Richtung liegen. Diese Zellen besitzen also eine Polarit~t, deren Achse mit einem

Root Hairs

“…The root epidermis of Arabidopsis, like other members of the family Brassicaceae, possesses a distinct position-dependent pattern of root hair cells and non-hair cells (Cormack, 1935;1949;Bunning, 1951;Dolan et al, 1994;Galway et al, 1994). Root hair cells are present outside the intercellular space between two underlying cortical cells (i.e., located outside an anticlinal cortical cell wall, called the "H" position), whereas non-hair cells are present over a single cortical cell (i.e., located outside a periclinal cortical cell wall, called the "N" position) (Figure 4).…”

Building a root: the control of patterning and morphogenesis during root development.

“…In other species, including many monocots, epidermal cell fate is linked to an asymmetric cell division, with the smaller daughter cell differentiating into a root hair cell and the larger daughter cell generating one or more mature hairless cells (Sinnott and Bloch, 1939;Avers, 1963;Cutter and Feldman, 1970). In a third group of plants, which includes Arabidopsis and other members of the Brassicaceae, a distinct position-dependent pattern of epidermal cell types is generated (Cormack, 1935;Bunning, 1951;Dolan et al, 1994;Galway et al, 1994). In this case, trichoblasts form in the crevice between underlying cortical cells (outside an anticlinal cortical cell wall), whereas atrichoblasts develop over a cortical cell (outside a periclinal cortical cell wall; Figures 2A and 26).…”

“…Indeed, three different experimental approaches show that epidermal cells that have embarked on one differentiation pathway can switch to the alternate pathway at a relatively late stage. These analyses include surgical experiments in which atrichoblasts can be induced to form root hairs when they are physically separated from the underlying cortical cells (Bunning, 1951), anatomical studies in which trichoblast daughter cells from rare longitudinal divisions develop as hairless cells (F. Berger, G. Hung, L. Dolan, and J.W. Schiefelbein, unpublished results), and pharmacological experiments in which hormone treatments induce root hair production on atrichoblasts (Tanimoto et al, 1995;.…”

A Common Position-Dependent Mechanism Controls Cell-Type Patterning and GLABRA2 Regulation in the Root and Hypocotyl Epidermis of Arabidopsis1

“…The formation of the root epidermis provides a simple model for investigating this problem in plants. In many species, two distinct cell types are formed during root epidermis development, root-hair cells and hairless cells (Cormack, 1949;Bunning, 1951;Cutter, 1978). The specification of cell fate in the root epidermis (i.e.…”

“…in contact with two underlying cortical cells) differentiate into root-hair cells, whereas cells located outside a periclinal cortical cell wall (i.e. in contact with a single cortical cell) differentiate into mature, hairless cells (Bunning, 1951;Cutter, 1978).…”