ROOT APICAL MERISTEMS OF FAGUS SYLVATICA

The concept of the quiescent centre and how it found support from work with X-rays. I. Historical perspectives

“…Clowes's first two publications deal with roots of beech (Fagus sylvatica) and their mycorrhiza (Clowes 1950(Clowes , 1951. Mycorrhiza and plant nutrition were topics of interest to JL Harley who, in 1938, had been appointed Demonstrator in the Botany School, Oxford University, where Clowes was then an undergraduate.…”

“…In theory, the method could also indicate something of the relative rates of division in the small group of cells which putatively co-located within the ontogenetic centre. When this method was applied to the beech roots (Clowes 1950), it was found that the ontogenetic centre was indeed the focus of the various cell files of plerome, periblem, and cap columella. Then, making the assumption that cells did not slide over one another (an assumption that becomes explicit only in Clowes's review of 1959b), it is evident that, for the cellular architecture of the root apex to be maintained, cells within the ontogenetic centre must grow and divide only slowly, or maybe not at all, whereas cells of the surrounding proximal and distal portions of the meristem, which are not subject to such constraint upon their rates of growth and division, could grow faster.…”

“…The staining procedure used a sequence of haematoxylin, safranin and crystal violet, which gave good definition not only of cell walls but also of nuclei and nucleoli (Clowes 1949). The weakly stained group of cells at the root apex was considered as a 'cytogenetic centre', or as an 'ontogenetic centre' (Clowes, 1950) or, later, as a cytogenerative centre' (Clowes, 1953(Clowes, , 1954b, all these terms being eventually superceded by 'quiescent centre' (Clowes 1956a), as documented by Dubrovsky and Barlow (2015).…”

The Cytogenerative Centre in Roots With Broad Columellas

“…It may be due to a decrease in size of the meristem such as occurs naturally (Clowes, 1950) or after the excision of part of the meristem. It also suggests that the meristem is more autonomous than is sometimes thought.…”

“…THEORIES OF THE NATURE OF THE CYTOGENERATIVE CENTREThe spatial organization and behaviour of the root apical meristem of Fagus sylvatica have been described from an analysis of the patterns of cell complexes which could be observed in sections through the meristem (Clowes, 1950). The complexes are groups of cells derived from a single cell, and from observing how the cells are arranged within the complex and how the complexes are arranged within the apex, it was possible to deduce the shape and behaviour of a multicellular cytogenerative centre or promeristem.…”