Plant regeneration from cultured immature embryos of early and late barleycultivars: 2. Morphological differentiation of embryos as an indicator of their competence for plant regeneration

The frequency of multiple plant regeneration (MPR) was studied in the calli derived from the embryos of three early-ripening and three late-ripening b arley (Hordella vulgare L.) cultivars differing in their size, the degree o f transparency, and morphological differentiation. The loss of embryonic ce ll capacity for plant regeneration in vitro coincided with the termination of morphological differentiation in the embryonic axis. In the early-ripeni ng cultivars, the differentiation of embryonic axes terminated earlier, at smaller sizes and higher transparency of embryos. In all cultivars, the ter mination of the differentiation of embryonic axes into plant organs was acc ompanied by changes in the coleoptile shape from spherical into semispheric al and by the loss of the coleoptile capacity for staining bright blue-gree n with toluidine blue. These coleoptile characteristics were chosen for the workable markers of embryo morphological differentiation in selecting the embryos with a high potential for plant regeneration in vitro.