Deterministic cellular descendance and its relationship to the branching of plant organ axes

Abstract

A double-wall map L-system, designated as S(5-5), was developed to simulate the cellular pattern found at the summit of shoot apices of Psilotum nudum. Commencing from a 3-sided autoreproductive founder cell, fives steps of simulation established a basic set of ten different cell types. Continuing the simulation beyond the fifth step revealed that, in addition to the regular production of new 3-sided cells, a group of autoreproductive 5-sided cells came into being. A close correspondence exists between the cells of the two-dimensional simulation and the two-dimensional cellular patterns found on the epidermis of the apices of Psilotum species. The 3-sided cells produced during the simulation correspond to the potentially organogenetic 3-sided cells that can be seen upon the apical surfaces. Successive generations of these 3-sided apical cells (which are actually 4-sided tetrahedral cells when viewed in three dimensions) and their immediate descendants are thought to be selected to organise the successive pairs of apices that bring about the repeated bifurcation of the Psilotum shoots. The 5-sided cells contribute to the cellular "pavements" which separate these pairs of organogenetic centres, each with their 3-sided apical cells. The cellular patterns simulated by the S(5-5) system may also correspond to the cellular patterns found on the surfaces of some other pteridophyte apices, including that of the rhizophores of Selaginella species. Tritiated-thymidine labelling of rhizophore apices revealed a group of nonproliferating cells that was associated with rhizophore bifurcation and which may correspond to a group of pavement cells. Nonproliferating cells, by regulating the siting of new organogenetic centres, may have evolved as an accompaniment to branching events such as the bifurcation of root and organ axes.

Plant roots: autopoietic and cognitive constructions

“…Then, in accordance with the operation of system S 5-5 , cell a proceeds to repeat the same sequence of cell production as does cell b, except that the handedness of its cell productions is the contrary to those from cell b. This feature of the notional cellular system agrees with the biological system (Barlow and Lück 2004). The similarity between the L-system mode of cell production and that observed in the biological material is strong.…”

“…This cell b is an analogue of a 3-sided structural initial, or apical cell; such a cell is characteristic of root and shoot apices of certain ferns. The operation of system S 5-5 was found to produce a sequence of notional cells which faithfully reproduce the spiral patterns of actual biological cells observable upon the apices of roots and shoots of the fern, Psilotum nudum (Barlow et al 2000, 2004a, Barlow and Lück 2004.…”

The botanical multiverse of Peter Barlow

“…Those studies often used sophisticated methods of analysis such as 'bootstrap' L-systems, as exemplified in his long-standing collaboration with Jacqueline and Hermann Lück [3,4,[6][7][8][9][10][11]. This marriage of mathematics and modelling to the 'old-fashioned', traditional observational botany approach [12] was a particular forte of Peter's that is also particularly evident in his lunisolar researches [see Extra-terrestrial influences on plant-life].…”

Early “Rootprints” of Plant Terrestrialization: Selaginella Root Development Sheds Light on Root Evolution in Vascular Plants

“…It is currently unknown which events are taking place to prepare Selaginella roots for branching. In addition, how two new ICs appear is still not clear: They are considered to emerge either after inactivation of the original IC ( Imaichi and Kato, 1989 ; Otreba and Gola, 2011 ), or alternatively, a second IC might be derived from the original IC ( Barlow and Lück, 2004 ). Investigation into the early branching events is required to answer this fundamental question.…”