Plant regeneration from cultured immature embryos of early and late barleycultivars: 1. Plant regeneration in the primary callus derived from immature embryos

The frequency of multiple plant regeneration (MPR) of cultured primary call i derived from developing embryos of 22 barley (Hordeum vulgare L.) cultiva rs differing in ripening time (the period between seedling emergence and ea r formation) was determined. The capacity for MPR was lower in the early-ri pening cultivars as compared to the late-ripening ones. Changes in embryo t ransparency within an intact ear (an index characterizing embryo developmen t) were monitored visually during the period between 6 and 12 days after ar tificial pollination in a climatic chamber. During this period, completely transparent embryos became opaque at the axis, then at the scutellum, and, finally, they became completely nontransparent. This process proceeded more rapidly in the early-ripening cultivars. We suggested that the cause of th e lower level of MPR in the early-ripening cultivars was the accelerated de velopment of their embryos and, as a result, the shortening of the period f or which they were capable of MPR.