Stomatal vs. genome size in angiosperms: the somatic tail wagging the genomic dog?
by Hodgson J. G., Sharafi M., Jalili A., Diaz S., Montserrat-Marti G., Palmer C., Cerabolini B., Pierce S., Hamzehee B., Asri Y., Jamzad Z., Wilson P., Raven J. A., Band S. R., Basconcelo S., Bogard A., Carter G., Charles M., Castro-Diez P., Cornelissen J. H. C., Funes G., Jones G., Khoshnevis M., Pérez-Harguindeguy N., Pérez-Rontomé M. C., Shirvany F. A., Vendramini F., S. Yazdani S., Abbas-Azimi R., Boustani S., Dehghan M., Guerrero-Campo J., Hynd A., Kowsary E., Kazemi-Saeed F., Siavash B.,Villar-Salvador P., Craigie R., Naqinezhad A., Romo-Diez A., de Torres Espuny L., Simmons E. (2010)
J. G. Hodgson1,†,*, M. Sharafi2, A. Jalili3, S. D ́ıaz4, G. Montserrat-Mart ́ı5, C. Palmer6, B. Cerabolini7, S. Pierce7, B. Hamzehee3, Y. Asri3, Z. Jamzad3, P. Wilson8, J. A. Raven9, S. R. Band8, S. Basconcelo10, A. Bogard6, G. Carter6, M. Charles6, P. Castro-D ́ıez5, J. H. C. Cornelissen11, G. Funes4, G. Jones6, M. Khoshnevis3, N. Pe ́rez-Harguindeguy4, M. C. Pe ́rez-Rontome ́5, F. A. Shirvany3, F. Vendramini4, S. Yazdani3, R. Abbas-Azimi3, S. Boustani3, M. Dehghan3, J. Guerrero-Campo4, A. Hynd6, E. Kowsary3, F. Kazemi-Saeed3, B. Siavash3, P. Villar-Salvador5, R. Craigie6, A. Naqinezhad2, A. Romo-D ́ıez12, L. de Torres Espuny5 and E. Simmons6
1 Peak Science and Environment, Station House, Leadmill, Hathersage, Hope Valley S32 1BA, UK,
2 Department of Biology, Faculty of Sciences, University of Mazandaran, Babolsar, Iran,
3 Research Institute of Forests and Rangelands, PO Box 13185- 116, Tehran, Iran,
4 Instituto Multidisciplinario de Biologıa Vegetal (CONICET – UNC) and F.C.E.F.y N., Universidad Nacional de Cordoba, Casilla de Correo 495, Vélez Sarsfield 299, 5000 Cordoba, Argentina,
5 Dept Ecologıa Funcional y Biodiversidad, Instituto Pirenaico de Ecologıa (CSIC) Aptdo. 202, E-50080 Zaragoza, Spain,
6 Department of Archaeology, University of Sheffield, Sheffield S1 4ET, UK,
7 Unità di Analisi e Gestione Biocenosi, Dipartimento di Biologia Strutturale e Funzionale, Universita` degli Studi dell’Insubria, Via J.H. Dunant, 3 – 21100 Varese, Italy,
8 Unit of Comparative Plant Ecology, Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK,
9 Division of Plant Sciences, University of Dundee at SCRI, Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, UK,
10 Ecologıa Agrıcola, Facultad de Ciencias Agropecuarias, Universidad Nacional de Cordoba, CC 509, 5000, Cordoba, Argentina,
11 Department of Systems Ecology, Faculty of Earth and Life Sciences, VU University, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands and
12 Institut Botànic de Barcelona, Parc Montjuıc, Av. dels Muntanyans s/n 08038, Barcelona, Spain
in Annals of Botany 105: 573–584, 2010 – doi:10.1093/aob/mcq011
† Background and Aims: Genome size is a function, and the product, of cell volume. As such it is contingent on ecological circumstance. The nature of ‘this ecological circumstance’ is, however, hotly debated. Here, we investigate for angiosperms whether stomatal size may be this ‘missing link’: the primary determinant of genome size. Stomata are crucial for photosynthesis and their size affects functional efficiency.
† Methods: Stomatal and leaf characteristics were measured for 1442 species from Argentina, Iran, Spain and the UK and, using PCA, some emergent ecological and taxonomic patterns identified. Subsequently, an assessment of the relationship between genome-size values obtained from the Plant DNA C-values database and measurements of stomatal size was carried out.
† Key Results: Stomatal size is an ecologically important attribute. It varies with life-history (woody species , herbaceous species , vernal geophytes) and contributes to ecologically and physiologically important axes of leaf specialization. Moreover, it is positively correlated with genome size across a wide range of major taxa.
† Conclusions: Stomatal size predicts genome size within angiosperms. Correlation is not, however, proof of causality and here our interpretation is hampered by unexpected deficiencies in the scientific literature. Firstly, there are discrepancies between our own observations and established ideas about the ecological significance of stomatal size; very large stomata, theoretically facilitating photosynthesis in deep shade, were, in this study (and in other studies), primarily associated with vernal geophytes of unshaded habitats. Secondly, the lower size limit at which stomata can function efficiently, and the ecological circumstances under which these minute stomata might occur, have not been satisfactorally resolved. Thus, our hypothesis, that the optimization of stomatal size for functional efficiency is a major ecological determinant of genome size, remains unproven.