ORIGINAL PAPER Ecophysiological performance of Calotropis procera: an exotic and evergreen species in Caatinga, Brazilian semi-arid Gabriella Frosi • Marciel Teixeira Oliveira • Jarcilene Almeida-Cortez • Mauro Guida Santos Received: 17 February 2012 / Revised: 24 July 2012 / Accepted: 1 August 2012 / Published online: 24 August 2012 Ó Franciszek Go ´rski Institute of Plant Physiology, Polish Academy of Sciences, Krako ´w 2012 Abstract To better understand the proliferation of Calotropis procera in a semi-arid region of northeastern Brazil (Caatinga), we designed two experiments to deter- mine which ecophysiological characteristics contribute to the species adaptive success. The first experiment was conducted with young plants under greenhouse conditions and three water regimes. The second experiment was conducted with adult plants under field conditions subject to regional seasonality. Young plants exhibited a high tolerance to water deficits, mainly because of their strong stomatal control, which was observed before any bio- chemical alterations in leaf metabolism. Only under full suspension of irrigation did the plants show a reduction in relative water content. Under field conditions, adult plants showed a high resilience to the semi-arid environment with respect to gas exchange and other measured biochemical parameters, including photosynthetic pigment, soluble sugars, amino acids and protein content, even under the low soil water availability of the dry season. This season featured high photosynthetically active radiation, low rel- ative humidity and high temperatures, and thus exposed plants to extreme differences between leaf and air tem- peratures. Calotropis procera remains green throughout the year, indicating that it has developed several means of tolerating the semi-arid climate. Furthermore, this species maintains a high photosynthetic rate despite reduced sto- matal conductance, which increases its water use effi- ciency, a fundamental characteristic for survival in this ecosystem. Keywords Drought tolerance Á Invasive species Á Gas exchange Á Stomatal control Introduction The Caatinga is a semi-arid tropical forest in northeastern Brazil, covers 734,478 km 2 and is the fourth largest veg- etation type in the country, after the Amazonian forest, the Cerrado, and the Atlantic forest (MMA 2002). This forest is considered one of ‘‘Earth’s last wild pla- ces’’ and one of the 37 extant wilderness areas in the world (Gil 2002). Rainfall is generally confined to the summer months (December to April), with accumulation ranging from 300 to 750 mm per year. Therefore, the native veg- etation of the Caatinga is mostly deciduous or semidecid- uous, with leaf-fall occurring during the dry season (Mansur and Barbosa 2000). The vegetation is hyperxer- ophilous with patches of deciduous forest and is predom- inantly composed of trees and branched underbrush. In recent decades, this ecosystem has suffered constant human disturbances, mainly related to woody species consumption as an energy source, thereby reducing the natural habitat. This scenario has favored the establishment of several exotic plants (Milton and Dean 2010), such as Calotropis procera. Calotropis procera (Ait.) R. Br. (Gentianales: Asclepi- adaceae) is a perennial Asian shrub that primarily repro- duces via seeds. In degraded ecosystems, C. procera is known to be a key resource provider for about 80 Communicated by J. Franklin. G. Frosi Á M. T. Oliveira Á M. G. Santos (&) Laboratory of Plant Ecophysiology, Department of Botany, Federal University of Pernambuco, Recife, PE 50670-901, Brazil e-mail: mauro.gsantos@ufpe.br J. Almeida-Cortez Laboratory Plant-Animal Interaction, Department of Botany, Federal University of Pernambuco, Recife, PE 50670-901, Brazil 123 Acta Physiol Plant (2013) 35:335–344 DOI 10.1007/s11738-012-1076-x