Seed germination and rising atmospheric CO2 concentration: a meta-analysis of parental and direct effects



Plant regeneration from seed is largely governed by germinability and speed of germination. These fitness components have received considerably less attention in CO2 research relative to studies of vegetative or reproductive output responses. Moreover, the limited literature has not been rigorously examined for generalizable patterns of responses and/or potential mechanisms. We used a meta-analytic approach to summarize literature results of seed germination characteristics in response to parental CO2 enrichment (eCO2). The direct effects of eCO2 on germination components were also analyzed. The data set came from 29 original research papers encompassing 64 species and 116 observations. Across all studies, parental eCO2 increased subsequent germination by 9%, but the responses varied among species by as much as 300%. The response was significantly higher in trees than in other life forms. With the exception of crops, parental eCO2 also increased germination rate in most life forms and functional groups. Despite a considerable interspecific variability, we found a positive correlation between germination success and seed mass responses to parental eCO2. Therefore, the observed diversity of regeneration success responses to parental eCO2 is partly controlled by the direction and magnitude of changes in seed mass.