No abstract

Ozone (O3) effects on the visual attraction traits (color, perception and area) of petals are described for Erodium paularense, an endangered plant species. Plants were exposed to three O3 treatments: charcoal-filtered air (CFA), ambient (NFA) and ambient + 40 nL L−1 O3 (FU+) in open-top chambers. Changes in color were measured by spectral reflectance, from which the anthocyanin reflectance index (ARI) was calculated. Petal spectral reflectance was mapped onto color spaces of bees, flies and butterflies for studying color changes as perceived by different pollinator guilds. Ozone-induced increases in petal reflectance and a rise in ARI under NFA were observed. Ambient O3 levels also induced a partial change in the color perception of flies, with the number of petals seen as blue increasing to 53% compared to only 24% in CFA. Butterflies also showed the ability to partially perceive petal color changes, differentiating some CFA petals from NFA and FU+ petals through changes in the excitation of the UV photoreceptor. Importantly, O3 reduced petal area by 19.8 and 25% in NFA and FU+ relative to CFA, respectively. In sensitive species O3 may affect visual attraction traits important for pollination, and spectral reflectance is proposed as a novel method for studying O3 effects on flower color.

Climate warming is recognized as a factor that threatens plant species in Mediterranean mountains. Tropospheric ozone (O3) should also be considered as another relevant stress factor for these ecosystems since current levels chronically exceed thresholds for plant protection in these areas. The main aim of the present study was to study the sensitivity of four Mediterranean perennial grasses to O3 and temperature based on plant growth, gas exchange parameters (photosynthesis—A, stomatal conductance—gs, and water use efficiency—WUE), and foliar macro- (N, K, Ca, Mg, P, and S) and micronutrients (B, Cu, Fe, Mn, Mo, and Zn) content. The selected species were grasses inhabiting different Mediterranean habitats from mountain-top to semi-arid grasslands. Plants were exposed to four O3 treatments in Open-Top chambers, ranging from preindustrial to above ambient levels, representing predicted future levels. Chamber-less plots were considered to study the effect of temperature increase. Despite the general tolerance of the grasses to O3 and temperature in terms of biomass growth, WUE and foliar nutrient composition were the most affected parameters. The grass species studied showed some degree of similarity in their response to temperature, more related with phylogeny than to their tolerance to drought. In some species, O3 or temperature stress resulted in low A or WUE, which can potentially hinder plant tolerance to climate change. The relationship between O3 and temperature effects on foliar nutrient composition and plant responses in terms of vegetative growth, A, gs, and WUE constitute a complex web of interactions that merits further study. In conclusion, both O3 and temperature might be modifying the adaptation capacity of Mediterranean perennial grass species to the global change. Air pollution should be considered among the driving favors of biodiversity changes in Mediterranean grassland habitats.