Autoreproductive cells and plant meristem construction: The case of the tomato cap meristem

Abstract

Root apical meristems are composed of two zones in which either formative or proliferative cell divisions occur. Within the formative zone, autoreproductive initial cells (a-cells) occupy distinctive locations. By means of graph-L-systems, the behavior of one such type of a-cells has been investigated, with particular reference to root caps within the developing primordia of lateral roots of Lycopersicon esculentum cultivated in vitro. Here, the a-cells constitute the "protoderm initials", cells which are found also in the root cap of many angiosperm species. A set of cuboidal (i.e., six-sided) a-cells develops early in the ontogeny of a lateral-root primordium. Then, according to both anatomical observations and theoretical simulations obtained by the application of graph-L-systems, sequential production of descendents from each a-cell leads to the formation of a new autoreproductive cell (a), a cap columella initial (c), and two mother cells (e and f) whose respective descendents differentiate as root epidermis and cap flank cells. In this graph-L-system, there is specification of the location of sister cells with respect to the three orthogonal directions of a cuboidal. In the early stage of root cap formation, only a few rounds of these formative cell divisions by each a-cell and its four types of descendents are required to provide the basic set of cells necessary for full cap development. After the lateral root emerges from the parent root, there may be a temporary cessation of the formative divisions of the a-cells which give rise to columella initials. Columella production is then supported entirely by its own independent set of autoreproductive c-initials. At the same time, division of the autoreproductive protoderm initial cell is directed towards maintaining the cap flank and the epidermal cell files. The regulation of the types of formative division by the a-cell may be represented by means of a division counter which may be specific for a given species.

Estimation of directional division frequencies in vascular cambium and in marginal meristematic cells of plants

“…The result is that the extra cells are eventually squeezed out from the initial ring. It is interesting to note that the apparent excess of anticlinal divisions in the initial cells would be expected if the cells conformed to a deterministic division programme, such as has been postulated for a similar autoreproductive system by Barlow et al . (2001).…”

“…In the earlier study of Barlow et al . (2001) it was proposed that the direction of cell production was determined according to the states attached to the walls of the dividing cell and that, following such a production, these states altered according to a definite sequence that could be codified as a set of directed production rules.…”

“…(In a periclinal division, the new division wall is orientated parallel to the cambial perimeter.) The initials are autoreproductive stem cells (Barlow 1997; Barlow et al . 2001) and are designated as a cells.…”

The simulation model of growth and cell divisions for the root apex with an apical cell in application to Azolla pinnata

“…In this aspect both shoot and root apices possessing one or more apical cells were investigated (Barlow et al 2000, 2001). Such analysis does not need simulation performed at the organ level.…”

Characteristics of Root Caps in Four Root Types of <i>Avicennia marina</i> (Forsk.) Vierh.

“…This condition appropriate to the research of [4] and the structural evidence obtained in studies of different root types indicates that the roots are effective in water and nutrient absorption. [34] describe a pattern of cell division in the cap meristem in detail. The regions considered were columella and flank meristem and the principles of the model may be regarded as general for the caps of roots, such as mangrove, with a closed meristem structure.…”