The branching pattern of the barley plant is analyzed and the anatomical structure of the resting barley embryo studied in longitudinal and cross-sections as well as by dissection techniques. The frequency and distribution of ethylmethane-sulfonate induced chloroplast and morphological seedling mutants were analyzed in spikes classified according to their ontogenetic relationship. The frequency with which two spikes segregated identical mutants was determined by pairwise comparisons of all spikes in each plant. In this way the frequency of mutant cluster sharing between spikes and spike groups was obtained.The absence of cluster sharing allows the recognition in the barley plant of 8 mutually exclusive mutant sectors which never had a mutant cluster in common. The anatomical analysis proves that the barley embryo contains at least 6 separate shoot meristems or prospective shoot meristems, which will constitute mutually exclusive mutant sectors in the plant. The combined genetical and anatomical analysis reveals that in large seeds there are always 9 meristems leading to 9 mutually exclusive mutant sectors. Up to 7 additional meristems leading to mutually exclusive mutant sectors can be present in the embryo of the seed. These will, however, not appear in plants under normal development.There are, according to the present analysis, 6 spikes for which 1 or 2 functional initial cells for their sporogenous tissue are already established in the embryo, i.e. at the time of mutagenic treatment. Except for these spikes all spikes belong to 6 shoot groups. The sporogenous tissue of any 2 spikes within these groups can arise from 1 functional initial cell in the embryo.
|Publication status||Published - 1966|