Warming and elevated CO₂ affect the relationship between seed mass, germinability and seedling growth in Austrodanthonia caespitosa, a dominant Australian grass

Abstract

While the influence of elevated CO 2 on the production, mass and quality of plant seeds has been well studied, the effect of warming on these characters is largely unknown; and there is practically no information on possible interactions between warming and elevated CO 2 , despite the importance of these characters in population maintenance and recovery. Here, we present the impacts of elevated CO 2 and warming, both in isolation and combination, on seed production, mass, quality, germination success and subsequent seedling growth of Austrodanthonia caespitosa, a dominant temperate C 3 grass from Australia, using seeds collected from the TasFACE experiment. Mean seed production and mass were not significantly affected by either elevated CO 2 or warming, but elevated CO 2 more than doubled the proportion of very light, inviable seeds (Po0.05) and halved mean seed N concentration (Po0.04) and N content (Po0.03). The dependence of seed germination success on seed mass was affected by an elevated CO 2 Â warming interaction (Po0.004), such that maternal exposure to elevated CO 2 or warming reduced germination if applied in isolation, but not when applied in combination. Maternal effects were retained when seedlings were grown in a common environment for 6 weeks, with seedlings descended from warmed plants 20% smaller (Po0.008) with a higher root : shoot ratio (Po0.001) than those from unwarmed plants. Given that both elevated CO 2 and warming reduced seed mass, quality, germinability or seedling growth, it is likely that global change will reduce population growth or distribution of this dominant species.

Mediation of seed provisioning in the transmission of environmental maternal effects in Maritime pine (Pinus pinaster Aiton)

“…However, in contrast with what occurred with total seedling biomass, this effect was not related to differences in seed provisioning. In accordance with previous studies (Hovenden et al, 2008), when considering the whole data set, we found that SM was negatively correlated with seedling RSR, with the smaller seeds leading to seedlings with greater RSR. However, when considering the effect of the maternal environment, we found that the stressful environment strongly determined a lower seedling RSR, even when the SM in that environment was the smaller.…”

“…Those SM-dependent epigenetic mechanisms, that is, a mixture of heritable and non-heritable maternal effects (sensu Boyko and Kovalchuk, 2011), are feasible whenever epigenetic regulation is resource dependent. Other authors have also found a significant SM Â maternal environment interaction on seedling growth, but they did not study the responsible mechanisms (Hovenden et al, 2008). Nevertheless, irrespective of the involved mechanisms, our results suggest that the maternal environment, rather than directly affecting the seedling total dry mass, modulates the extent to which the seedling phenotype depends on the SM, that is, a regulatory maternal effect.…”

“…Warmer maternal environments have been found to produce offspring with greater RSR in a grass species (Hovenden et al, 2008). The two maternal environments of the present study not only differed, however, in the temperature regime but also had extremely different edaphic properties (Cendán et al, 2012), with the warmer environment also having the best quality soils.…”

“…Previous studies have also shown that the maternal abiotic environment can modulate seedling biomass allocation (Hovenden et al, 2008;Sultan et al, 2009). Warmer maternal environments have been found to produce offspring with greater RSR in a grass species (Hovenden et al, 2008).…”

“…Several methods have been used to account for this potential bias in quantitative genetic studies. Including SM as a covariate in the statistical analyses has been probably the most frequent (Hereford and Moriuchi, 2005;Hovenden et al, 2008;Cendán et al, 2012) but this method is generally insufficient to cover all maternal effects, as effects unrelated to seed provisioning remain unaccounted for (Cendán et al, 2012). Alternatively, maternal effects may be controlled by growing parental genotypes in a common environment for at least one generation before genetic testing (Bischoff and Mueller-Schaerer, 2010).…”