Aroma profile and morphological analysis of Salvia elegans grown in Nemo's Garden® biospheres

Nemo’s Garden® biospheres are underwater greenhouses: they represent an alternative system of agriculture, especially dedicated to those areas where environmental conditions, economical or morphologic reasons make plant growth extremely difficult. The aim is to utilize seas and oceans as viable areas for plant growth. One of the species grown in these biospheres was Salvia elegans Vahl, also known as “pineapple sage”. It has been grown inside a biosphere, both in pot and in a hydroponic system. The phytochemical analyses, performed by means of Head-Space Solid Phase Micro-Extraction (HS-SPME)[1], evidenced differences in the spontaneous volatile emission of the Salvia samples. Volatiles from both the Nemo’s Garden samples are dominated by sesquiterpene hydrocarbons, with differences in terms of type and relative abundances. The most abundant volatile organic compound (VOC) in the hydroponic sample was trans-α-bergamotene, followed by viridiflorene. This latter was the most represented VOC in the potted specimen, along with β-caryophyllene. A different emission pattern was evidenced by the potted control sample: it was rich in sesquiterpene hydrocarbons as well, but in lower amounts; it also shows a relevant presence of nonterpene derivatives, mainly n-alkanes. As for the Nemo’s garden potted specimen, the most abundant VOCs in the control sample are viridiflorene and β-caryophyllene. The combined use of light and electron microscopy allowed to describe the micromorphology, distribution pattern and histochemistry of the glandular indumentum of S. elegans leaves: peltate trichomes and three types of capitate trichomes were detected. A general morphological consistency of the secreting hairs, and of the secretory products as well, resulted from our study, indicating that the biosphere habitat did not affect the indumentum features in both potted and hydroponic cultivation methods. The different patterns in the emission profiles of the specimens permitted to hypothesize that the biosphere conditions induced metabolic changes in the secondary metabolites pathways. Light, humidity and temperature played a key-role in the production of these compounds, as they represented the plant reaction to the environment. On the other hand, the micromorphology did not show differences in comparison with the control sample