An investigation into the anatomy of the shoot apex of Petunia hybrida in connection with the results of transformation experiments

From observations of flower colour chimeras of Petunia the conclusion can be drawn that dominant alleles of corolla colour genes can only express themselves in those cells in which these alleles are present. Anatomical studies of shoot apices of eight-day-old seedlings show that at this stage of development of the plant three independent cell layers are already present in the shoot apex, viz., two tunica layers and a corpus. In his interpretation of the results of his transformation experiments with Petunia, Hess did not take the existing differentiation of the shoot apex in his seedling material into account.