ORIGINAL PAPER Effects of UV radiation and water limitation on the volatile terpene emission rates, photosynthesis rates, and stomatal conductance in four Mediterranean species Joan Llusia • Laura Llorens • Meritxell Bernal • Dolors Verdaguer • Josep Pen ˜ uelas Received: 12 January 2011 / Revised: 26 September 2011 / Accepted: 18 October 2011 / Published online: 24 November 2011 Ó Franciszek Go ´rski Institute of Plant Physiology, Polish Academy of Sciences, Krako ´w 2011 Abstract This study examined the effects of the combi- nation of UV radiation and water limitation on the leaf photosynthesis, stomatal conductance, and terpene emis- sions of four Mediterranean species. 1-year-old seedlings of these Mediterranean species [Daphne gnidium L., Pis- tacia lentiscus L., Ilex aquifolium L. and Laurus nobilis L.] were grown under one of three UV treatments (without UV, with UVA, or with UVA ? UVB) and two watering regimes (high and low water supply). In general, UV treatments did not affect significantly leaf photosynthesis or stomatal conductance, although UVA and UVB radia- tion in September led to a reduction in leaf stomatal con- ductance in D. gnidium. Leaf photosynthesis rates did not differ significantly between the two watering treatments, even though, in three of the species, leaf stomatal con- ductance was significantly higher among the well-watered plants. The effects of UV on terpene emissions were spe- cies-specific; D. gnidium had the highest terpene emission rates when grown under UVA ? UVB radiation, which was also true for L. nobilis in September. Overall, UV treatments did not have a significant effect on total terpene emission rates in I. aquifolium, but UVB and UVA in July and September, respectively, reduced emission rates in P. lentiscus. A limited water supply reduced the terpene emission rates in D. gnidium, increased emissions in L. nobilis, and did not affect the emission rates in the other two species. Keywords UV radiation Á Mediterranean plants Á Monoterpenes Á Sesquiterpenes Á Terpene emission rates Abbreviations UVA Ultraviolet A UVB Ultraviolet B UV0 Without UV HWT High water treatment LWT Low water treatment Introduction In a rapidly changing world, changes in land use, increases in atmospheric CO 2 , tropospheric ozone, nutrient avail- ability, water limitations and UV radiation affect terpene emission rates by plants (Pen ˜uelas and Staudt 2010). Depletion of stratospheric ozone has increased the level of UVB radiation that reaches Earth; yet, little is known about the combined effects of UV radiation and water limitation on terpene emissions (Pen ˜uelas and Staudt 2010). UV irradiance affects nearly all organisms and several environmental processes, with the effects differing among wavelengths. Within the electromagnetic spectrum, wave- lengths of 320–400 nm are UVA radiation, and the radia- tion at shorter wavelengths (280–320 nm) is UVB. UVA radiation was thought to have little biological effects (Caldwell 1971) but, more recently, laboratory and field Communicated by J. Zwiazek. J. Llusia (&) Á J. Pen ˜uelas Global Ecology Unit CREAF-CEAB-CSIC Center for Ecological Research and Forestry Applications, Edifici C, Universitat Auto `noma de Barcelona, 08193 Bellaterra, Spain e-mail: j.llusia@creaf.uab.cat L. Llorens Á M. Bernal Á D. Verdaguer Department of Environmental Sciences, Faculty of Sciences, University of Girona, Campus de Montilivi, s/n, 17071 Girona, Spain 123 Acta Physiol Plant (2012) 34:757–769 DOI 10.1007/s11738-011-0876-8