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A B S T R A C T Pinwheel flowering African violets are bicolor forms that have a patterned arrangement of colors on the corolla segments. A median band of one color extends radially from the central portion of the corolla on each corolla segment and contrasts with the marginal color. In vitro culture of various tissues was accomplished, and observation of the flowering patterns of the regenerated plants supports the hypothesis that the cultivars 'Valencia', 'Dardevil', and 'Desert Dawn' are periclinal chimeras. Adventitious plants display a high proportion of monochromatic flowers of the same color as the lateral margin of the corolla segments. Petiole cultures from which the epidermal layers were removed yielded plants with flowers of the color of the central stripe of the corolla segments. Pinwheel flowering plants were regenerated through short-term culture of whole inflorescences, suggesting that the African violet inflorescence may possess axillary vegetative meristems. These results support the contention that adventitious shoots may arise from the epidermal layer only (L.I), or with the participation of the epidermal and subjacent layers (L.I and L.II). These results contradict the recent conclusion that all three histogen layers of African violet participate in adventitious shoot organization.

Plants of the foliarly variegated cultivar Saintpaulia ionantha Tommie Lou and the florally variegated cultivar Candy Lou were regenerated through tissue culture from leaf sections, petal sections, and subepidermal tissue. This provided explants with derivatives of all histogen layers of the shoot apex, layers I and II only, and layers II and III only. Over 1,000 plants of Tommie Lou and Candy Lou were grown to flowering. A low level of phenotypic variation was observed, but in no case could this be attributed to the separation of genotypically distinct cell lines. The foliar variegation pattern of both cultivars was stable through in vitro propagation. In contrast, the chimeral components of the flower color pattern in Candy Lou separated during regeneration. These data demonstrate that Tommie Lou-type foliar variegation is not caused by periclinal chimerism and that all leaf cell layers possess the genetic information necessary to produce variegated foliage. The production of all green and all white plants from a radiation-induced periclinal chimera demonstrated that the system used could detect chimeral separation. These results support the contention that adventitious shoots in Saintpaulia almost always differentiate in vitro from a derivative(s) of a single histogen layer, and this layer is usually the LI.

KRAUS, E. J., NELLIE A. BROWN, AND K. C. HAMNER. 1936. Histological reactions of bean plants to indoleacetic acid. Bot. Gaz. 98: 370-419. LEVINE, M. 1950a. The growth of normal plant tissue in vitro as affected by chemical carcinogens and plant growth substances. I. The culture of the carrot taproot meristem. Amer. Jour. Bot. 37: 445-470. . 1950b. The growth of normal plant tissues as affected by chemical carcinogens and plant growth substances. III. The culture of sunflower and tobacco stem segments. Bull. Torrey Bot. Club 77: 110-132. PIE:iRCE, G. J. I893. On the structure of some phaneroganmiic parasites. Ann. Bot. 7: 291-327. PRIESTLEY, J. H. AND C. F. SWINGLE. 1929. Vegetative propagation from the standpoint of plant anatomy. U. S. Dept. Agr. Tech. Bull. 151. SCHUMACHER, W. 1934. Die Absorptionsorgane von Cuscuta odorata und der Stoffiibertritt aus den Siebrohen der Wirtspflanze. Jarb. Wiss. Bot. 80: 79-91. SIEGLER, E. A. AND J. J. BOWMAN. 1939. Anatomical studies of root and shoot primordia in 1-year apple roots. Jour. Agric. Res. 58: 795-803.