Seed germination and rising atmospheric CO 2 concentration: a meta‐analysis of parental and direct effects

Summary Plant regeneration from seed is largely governed by germinability and speed of germination. These fitness components have received considerably less attention in CO 2 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 CO 2 enrichment ( e CO 2 ). The direct effects of e CO 2 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 e CO 2 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 e CO 2 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 e CO 2 . Therefore, the observed diversity of regeneration success responses to parental e CO 2 is partly controlled by the direction and magnitude of changes in seed mass.