[Physiological genetics of quantitative characters in Arabidopsis thaliana (L.) Heynh. : Part 3. Dauermodifications of pleiotropic effects of homoallelic genes].

The genephysiological and developmental basis of "Dauermodifications" (DM) have still not been explained. In particular definite evidence for DM in plastids is lacking up to now. Moreover no attention has been paid to the connections with the problem of quantitative gene effects. For that reason mutants of the nuclear gene ch in Arabidopsis thaliana (L.) Heynh., quantitatively defective in chlorophyll b were tested during seven generations under continuous yellow radiation (λ < 550 nm) expecting DM.The following results were obtained: 1) The main effects of the homoalleles ch (+), ch (1) and ch (2) on the reactions of chlorophyll transformation, especially on chlorophyll b-synthesis, cannot be modified permanently. 2) DM in certain accessory effects of the gene ch, i.e. carotinoid content (CC), apparent radiation energy use (EAG) and net assimilation rate (NAR) were induced by the applied radiation. These modifications are quantitative and cannot be restituted in the following generation after return to normal light.The induced DM affects phenotypic characters of the plastids which may result from biochemical regulation modified at the level of translation. The effects of multiple interactions between the allelic condition of the gene ch, the rest of the nuclear genes, the carriers of the extrachromosomal gene information, and the inducing environmental factor must be considered.