Causes of flower colour patterns with a focus on chimeral patterns

Colour patterns in flowers are of ornamental value and are important for histological studies. Similar flower patterns may have different causes. Bicoloured flowers may result from genetically inherited patterns, instable alleles of floral genes, infections, or chimeral dispositions. A transgenic Petunia Juss. serves as an example of an epigenetic chimera. Bicoloured cultivars of Angelonia Humb. et Bonpl., Pelargonium L´Herit. ex Ait., Petunia, and Saintpaulia H. Wendl. and other species are examined in terms of their flower colour pattern. The investigation of the causes of flower patterns is based on inheritance analysis (self-pollination), double marking of the different apex layers, grafting and somatic segregation (spontaneous and by in vitro callus culture). In the case of chimerally determined flower patterns, conclusions about the participation of apex layers in the histogenesis of flower tissues can additionally be drawn by apex layer double marking.