Shoot apical meristems and mutation: fixation of selectively neutral cell genotypes

摘要: Shoot apical meristems are interpreted as either structured, that is having a permanent set of initials, or stochastic, initials which represent ". . momentary representatives the continuous meristematic residue at apex relevant layer zone" (Newman, 1965). The two main parameters stochastic growth average number (cz) and mitotic cycles (r) their daughter cells prior to random selection subsequent initials. Mathematical analysis computer simulation studies have shown if one starts with 1 mutant initial cx1 nonmutant eventually mosaic plant results. frequency shoot apices composed 1/CY only ( cx)/cx. These asymptotics attained after considerable growth, thus mericlinal chimeras can persist for many nodes give appearance present. IN TERMS mutation analysis, be divided into groups: 1) consisting single, readily identified cell; 2) based upon indeterminate numbers cannot cytologically. Apical-cell-based characterize vascular cryptogams, whereas without an cell found in most seed plants (Popham, 1951; Bierhorst, 1977). Because regular segmentation patterns ontogeny apical-cell-based meristems, persistent impossible. Any passed on mitotically all derivative cells, tissues, organs and, thus, soon characterized by genotype. Meiotic spores collected from such will segregate wildtype genotypes 1:1 ratios (Klekowski Klekowski, 1982; 1984). In fate somatic mutations not obvious. When has genotype, unstable chimera results may ' Received publication 31 January 1983; accepted June 1983. We grateful Drs. L. Fukshansky H. Mohr Freiburg University valuable discussions criticisms ideas presented here. senior author (E.J.K.) would like thank Alexander von Humboldt Stiftung support Dr. his gracious hospitality. some period growth. With continued ofthe meristem, three outcomes possible: genotype lost; increase so meristem mutant; 3) stable form periclinal common angiosperms (Satina, Blakeslee Avery, 1940). latter situations referred "mutation fixation" former loss." mathematical modeling fixation loss various kinds subject this communication. Apical encompass very broad range anatomical ontogenetic (for recent survey, see Clowes, 1961). Although diversity importance taxonomic, phylogenetic, morphogenetic studies, aspects need considered terms loss: whether structured stochastic. sectors certain indicated investigators there relatively resident distal point (see Stewart, 1978 review). Such described "structured" A more "stochastic" view been proposed other (Soma Ball, 1964; Newman, 1965; Wardlaw, 1968; Esau, authors