Maternal and direct effects of elevated CO 2 on seed provisioning, germination and seedling growth in Bromus erectus

Abstract

Elevated CO can affect plant fitness not only through its effects on seed production but also by altering the quality of seeds and therefore germination and seedling performance. We collected seeds from mother plants of Bromus erectus grown in field plots at ambient and elevated CO (m-CO, maternal CO) and germinated them in the greenhouse in a reciprocal design under ambient and elevated CO (o-CO, offspring CO). This design allowed us to examine both the direct effects of elevated CO on germination and seedling growth and the indirect (maternal) effects via altered seed quality. Elevated m-CO significantly increased seed mass and increased the C:N ratio of seeds from field-grown plants. Percentage and rate of germination were not affected by the m-CO or o-CO treatments. Similarly, elevated m-CO had no significant effect on seedling size as estimated by the total leaf length. When differences in seed mass were adjusted by using seed mass as a covariate in ANOVA, a negative effect of m-CO on seedling size appeared which increased with increasing seed mass (significant covariate×m-CO interaction). This may indicate that the advantage of increased seed mass at elevated m-CO was offset by the reduced concentration of nitrogen (and possibly other nutrients) in these seeds. In contrast to m-CO, elevated o-CO greatly increased seedling size, and this stimulatory effect of elevated o-CO was found to increase with increasing seed mass (significant covariate×o-CO interaction). Taken together, these results suggest that in B. erectus transgenerational effects of elevated CO are relatively small. However, other factors (genetic and environmental) that contribute to variation in seed provisioning can critically influence the responsiveness of seedlings to elevated CO.

Can elevated CO2 modify regeneration from seed banks of floating freshwater marshes subjected to rising sea-level?

“…Our findings differ somewhat from germination studies of non-wetland species, which generally conclude that germination is little affected by elevated CO 2 (Garbutt et al, 1990;Huxman et al, 1998;Steinger et al, 2000;Poorter & Navas, 2003). In these terrestrial studies, a lack of germination density response to elevated CO 2 has been attributed partly to the fact that the CO 2 levels of terrestrial soils are higher than in the atmosphere (Bazzaz, 1979).…”

The effects of CO2 and nutrient enrichment on photosynthesis and growth of Poa annua in two consecutive generations

“…Negative effects of CO 2 on seed quality were also reported for the related species Bromus erectus (Steinger et al 2000). However, these effects did not lead to transgenerational effects of CO 2 , possibly because reduced seed quality coincided with increased seed size under conditions of elevated CO 2 (Steinger et al 2000). In contrast, a study of spring wheat (Tritium aestivum L.) showed that this plant species did not respond to elevated CO 2 during the first generation.…”

“…This can be explained by a negative effect of elevated CO 2 on seed size and the nutritional quality of seeds, which results in reduced photosynthetic rates of the next-generation seedlings (Huxman et al 2001). Negative effects of CO 2 on seed quality were also reported for the related species Bromus erectus (Steinger et al 2000). However, these effects did not lead to transgenerational effects of CO 2 , possibly because reduced seed quality coincided with increased seed size under conditions of elevated CO 2 (Steinger et al 2000).…”

“…Curtis et al 1994;Farnsworth and Bazzaz 1995;Andalo et al 1996;Steinger et al 2000;Kinugasa et al 2003;Hikosaka et al 2011). By affecting the reproductive output of a plant, the effects of CO 2 on plants can extend beyond a single growth period (Steinger et al 2000;Lau et al 2008).…”

“…Bezemer et al 1998;Huxman et al 1998Huxman et al , 2001Steinger et al 2000;Ward et al 2000;Schulte et al 2002;Derner et al 2004;Lau et al 2008). For example, seedlings of the annual grass Bromus madritensis respond to elevated CO 2 by increasing their growth rate, but this increase is less when the parent plant was also grown at elevated CO 2 than when the parent plant was grown at ambient CO 2 (Huxman et al 1998).…”