Mangrove genetics .4. Postzygotic mutations fixed as periclinal chimeras

Red mangrove (Rhizophora mangle) has shoot apices with a tunica-corpus organization; consequently somatic mutations are often manifested as complete or partial periclinal chimeras. Trees with branch systems exhibiting such chimeras for chlorophyll deficiency are rare in natural populations. Less than 0.1% of red mangroves in Puerto Rico exhibit such chimeras. The detailed analysis of one such chimera (R35) revealed a number of unique characteristics. The mutant exhibited cytoplasmic inheritance, a pattern consistent with a plastid genome mutation. On the basis of ultrastructural and confocal fluorescence analysis of the guard cells and histological patterns in the apices and leaves, the mutant is in the LI histogen of the shoot apex (outer tunica). The LI in red mangrove gives rise to cells that can divide periclinally; thus cell lineages of the LI develop into sporogenous tissues in the flowers and mesophyll cells along the leaf margins. In both of these characteristics, red mangrove appears similar to some monocot species.