Volatile profile of perennial leaves of seven cultivated species of Ceratozamia (Cycads)

Ceratozamia (Zamiaceae) is a genus of New World Cycads, containing more than 20 species distributed in eastern and southern Mexico, with extensions into Central America [1]. Morphology, anatomy, and molecular data allowed resolution of some aspects of species relationships, suggesting phytogeographic hypotheses [2]. Renewed interest in cycads has also resulted in works focused on phytochemical topics [3 and literature therein], however data on the volatile emission profiles lack. Seven Ceratozamia species belonging to clade “C” [2] and cultivated in a cold greenhouse at the Florence Botanic Garden were investigated: Ceratozamia fuscoviridis D. Moore, Ceratozamia hildae Landry & M. Wilson, Ceratozamia kuesteriana Regel, Ceratozamia latifolia Miq., Ceratozamia longifolia Miq., Ceratozamia mexicana Brongn., Ceratozamia vulgaris J. Schust. Perennial leaves were screened in February, July and September 2011 for the emission of volatile organic compounds (VOCs) by means of headspace solid phase microextraction coupled with gaschromatography and mass spectrometry (HS-SPME-GC/MS); two leaflets per species were sampled from coetaneous leaves, and analysed. In this study we assessed and compared the volatile profiles among species and across sampling periods, with the main objective to collect preliminary information to evaluate the potentiality of VOCs for taxonomic purposes. The VOC analysis revealed the emission of overall 199 compounds, of which 144 identified. The unknown compounds dominated the volatile profiles, accounting for about 27%, followed by aldehydes, terpenes, alcohols, ketones and esters. The highest number of compounds (115) was found in C. fuscoviridis, the lowest (91) in C. longifolia. In all the examined species, February profiles invariably exhibited the major amount of volatiles in comparison to July and September. Statistical data processing proved: (i) a low level of diversity among the VOC profiles of the examined species referred to each collection time; (ii) a great variability in the temporal emission patterns of all the species across the three sampling periods. These evidences revealed the predominance of the environmental components at the study area in affecting the volatile profiles of Ceratozamia species, at the expense of the metabolic resilience related to the different climatic conditions of the native regions. Possible ecological roles of the VOC temporal variation in relation to the plant phenological stages are discussed.