Shoot Apical Meristems and Mutation: Selective Loss of Disadvantageous Cell Genotypes

The previously described mathematical model of stochastic apical meristem growth (Klekowski and K.‐Fukshansky, 1984) was used to study the fate of initials with disadvantageous genotypes. Such initials are heterozygous for somatic mutations with some dominant effects and consequently have lessened viabilities (V < 1) in contrast to initials with only wild type alleles (V = 1). Computer simulation studies show a dramatic increase in the loss of such mutations with increasing number of apical initials and/or the number of cell divisions of the initials and their daughter cells before the subsequent set of initials are chosen. Among plants with stochastic apices (most seed plants and some lower vascular plants), the major phylogenetic and ontogenetic trends are correlated with the development of apices with greater buffering against mutations. Whether these correlations reflect a causal relationship is of course unknown.