Stomatal traits in Iberian populations of Osmunda regalis (Osmundaceae, Polypodiopsida) and its relationship with bioclimatic variables

Abstract

Stomata are very conserved structures in plants, which allows and control the gas exchange. This ecophysiological fact appears to be critical in the ecology and adaptation of plants to environment. Plant individuals can, among other issues, adjust size and density of the stomata to adapt themselves to hydric, thermic and light regimes. In turn, this led to the reduction of transpiration and control of water losses, which is crucial in areas with Mediterranean climate. The fern Osmunda regalis has populations in both biogeographical regions of the Iberian Peninsula (Eurosiberian and Mediterranean regions), but when locations are highly continental the populations are scarce and isolated. The objective of this study is to characterize the stomatal morphological traits in both regions, to detect possible adaptations in individuals occurring in Mediterranean locations. 26 individuals of 17 different populations were sampled. Applying microscopic techniques, 4447 observations of length and width, and 234 of density and PCI were done. The sampling spots were characterized by two bioclimatic indices of Emberger and Gorzynski, and also mean maximum and minimum temperature values were obtained. All the information was included in a dataset that was statistically analyzed with the software SPSS. Our results show that Osmunda regalis fronds have higher PCI and density values in the Eurosiberian region, as expected. Gorczynski continentality index (K), and the mean maximum and minimum annual temperatures influences over stomatal traits. This is clearly informing that in the Mediterranean region, the temperature is an important factor that triggers stomatal adaptations of O. regalis to continental locations with higher levels of environmental stress. On the contrary, Emberger pluviometric index (Q) seems to be less explicative by its own. Perhaps this is related with the habitat of O. regalis in soils with high freatic level, fact which could lead to a more independent stomata from rainfall.