NUCLEAR GENE-INDUCED PLASTOME MUTATIONS IN OENOTHERA HOOKERI. II. PHENOTYPIC DESCRIPTION WITH ELECTRON MICROSCOPY

The nuclear gene pm of Oenothera hookeri T. & G. strain Johansen increases the frequency of plastome mutations. These plastome mutations are visible because they form variegation sectors. A distinctive feature of the pm system is the large number of different phenotypes induced by the plastome mutator. The fine structure of four plastome mutants has been studied using electron microscopy. Each of the four mutants had a unique phenotype which was characterized by the amount of thylakoid development, the number of plastoglobuli, and the dilation of thylakoids with age. The developmental sequence of the phenotype of one of the mutants was studied by following plastid development in progressively larger leaves. The phenotypes of the pm-induced mutants are generally similar to those of spontaneous plastome mutations described in the literature.