Direct and Maternal Effects of Elevated CO2on Early Root Growth of GerminatingArabidopsis thalianaSeedlings

Individuals of Arabidopsis thaliana , collected in different natural populations, were grown in controlled and elevated CO 2 in a glasshouse. Following germination, root growth of progeny of different lines of these populations was studied in control and elevated atmospheric CO 2 . No significant direct effect of atmospheric CO 2 concentration could be demonstrated on root growth. An important parental effect was apparent, namely that root length and branching were decreased in seeds collected from a mother plant which had been grown in elevated CO 2 . This was correlated with smaller seeds, containing less nitrogen. These parental effects were genetically variable. We conclude that CO 2 may affect plant fitness via parental effects on seed size and early root growth and that the genetic variability shown in our study demonstrates that Arabidopsis populations will evolve in the face of this new selective pressure.