Effect of growth temperature on biomass production of nearly isonuclear triazine-resistant and -susceptible common groundsel (Senecio vulgaris L.)

Abstract. The effect of growth temperature on biomass production and photosynthesis of nearly-isonuclear triazine-resistant and -susceptible Senecio vulgaris L. bio-types was investigated. Plants were grown in growth chambers with day/night temperatures of 13/8, 20/15 and 30/25°C, and were harvested 35, 42, 49 and 56d after planting (DAP). The S biotype produced more shoot dry weight than the R × S_BC6 biotype, and the S × R_BC6 biotype produced more shoot dry weight than the R biotype at all DAP and growth temperature combinations. The S and S × R_BC6 biotypes had greater photosynthetic rates than the R X S_BC6 and R biotypes, respectively. Thus, plants containing the susceptible chloroplast genome produced more biomass and had greater photosynthetic rates than those with the resistant chloroplast genome, when in association with the same nuclear genome. There was no differential temperature effect on biomass production of isonuclear plants possessing resistant or susceptible chloroplast genomes. However, there was a large differential temperature effect on the amount of biomass produced by plants containing different nuclear genomes (R or S) in association with the same chloroplast genome. The R nuclear genome appeared to be better adapted to cooler growth temperatures while the S nuclear genome was better adapted to warmer growth conditions.