GENOME AND PLASTOME EFFECTS ON PHOTOSYNTHESIS PARAMETERS IN OENOTHERASPECIES OF DIFFERENTIAL LOW-TEMPERATURE TOLERANCE

The influence of the plastid genome (plastome) on the temperature depe ndence of chlorophyll fluorescence parameters was studied in four Oeno thera species from climatically different habitats. Equipped with thei r natural plastome, the species could be arranged with respect to thei r low-temperature tolerance in the order Oe. 'villosa' (plastome I) ap proximate to Oe. argillicola (V) > Oe. grandiflora (III) > Oe. elata s sp. hookeri (I). Exchanging the naturally occurring plastome with thos e from other species did not result in changes of the photosynthetic p erformance of the genotypes, except for decreasing pigment contents an d photosynthesis rates (on area basis) in Oe. elata ssp. hookeri with plastome III. Furthermore, plastome exchange in Oe. elata ssp. hookeri and in Oe. grandiflora did not affect kinetic properties of purified ribulose-1,5-bisphosphate carboxylase/oxygenase (EC 4.1.1.39), indicat ing that the gene for the large subunit of this enzyme has remained co nserved during plastome evolution in Oenothera. It is concluded that t he evolution of the plastome in North American Oenothera spp. did not influence the temperature adaptation of the photosynthetic apparatus, but that the latter is governed by effects residing in the nuclear gen ome.