Stomatal density responses of temperate woodland plants over the past seven decades of CO 2 increase: a comparison of Salisbury (1927) with contemporary data

• Published in: American Journal of Botany
• Main Authors: Beerling, D. J., Kelly, C. K.
• Other Authors: British Ecological Society Small, U.S. National Science Foundation
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1997
• Subjects: Plant Science; Genetics; Ecology, Evolution, Behavior and Systematics; ice core
• Online Access: http://dx.doi.org/10.2307/2446619; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.2307%2F2446619; http://onlinelibrary.wiley.com/wol1/doi/10.2307/2446619/fullpdf

We investigated the possible effect of recent (1927–1995) increases in the concentration of atmospheric CO 2 on the stomatal densities of leaves of a wide range of tree, shrub, and herb species ( N = 60) by making new measurements for comparison with corresponding data reported by E. J. Salisbury in 1927—a time when ice core studies indicate CO 2 concentrations ~55 µL/L lower than present. A detailed intraspecific study of the herb Mercurialis perennis showed plants of M. perennis in a Cambridgeshire woodland in 1994 had significantly lower stomatal densities, irrespective of leaf insertion point, compared with their 1927 counterparts. Comparisons made across species using evolutionary comparative methods (independent contrasts) revealed a significant ( P < 0.01) decrease in stomatal density over the past 70 yr. The results of both the inter‐ and intraspecific comparisons are consistent with the hypothesis that historical CO 2 increases have influenced leaf morphology in a manner consistent with recent experiments and the palaeoecological record. Further analyses suggested that the strength of the stomatal density response was independent of life form but dependent on “exposure” and the initial leaf stomatal density. Consequently, firmer predictions for future changes in stomatal density across all species, expected as a possible result of anthropogenically related CO 2 increases, may now be possible.