Text by Lauri Laanisto
It´s not only trees and other woody species that we study in our lab(s). Occasionally also herbaceous plants. This week came out, in Journal of Plant Growth Regulation, paper led by our Chinese postdoc Yifan Jiang, who together with Jiayan, Shuai and Ülo (all from our workgroup) studied the volatile emissions of basil. To be more precise, which organs emit which molecules and how much. Intraspecific volatile variability of 41 compounds (check table 2)! It´s a pretty chemical text…
Not yet full citation: Jiang, Y., Ye, J., Li, S., & Niinemets, Ü. (2016) Regulation of Floral Terpenoid Emission and Biosynthesis in Sweet Basil (Ocimum basilicum). Journal of Plant Growth Regulation, DOI 10.1007/s00344-016-9591-4 (link to full text)
Past studies have focused on the composition of essential oil of Ocimum basilicum leaves, but data on composition and regulation of its aerial emissions, especially floral volatile emissions, are scarce. We studied the chemical profile, within-flower spatial distribution (sepals, petals, pistils with stamina, and pedicels), diurnal emission kinetics and effects of exogenous methyl jasmonate (MeJA) application on the emission of floral volatiles by dynamic headspace collection, and identification using gas chromatography-mass spectrometry (GC–MS) and proton-transfer reaction mass spectrometry. We observed more abundant floral emissions from flowers compared with leaves. Sepals were the main emitters of floral volatiles among the flower parts studied. The emissions of lipoxygenase compounds and monoterpenoids, but not sesquiterpene emissions, displayed a diurnal variation driven by light. Response to exogenous MeJA treatment of flowers consisted of a rapid stress response and a longer-term acclimation response. The initial response was associated with enhanced emissions of fatty acid derivatives, monoterpenoids, and sesquiterpenoids without variation of the composition of individual compounds. The longer-term response was associated with enhanced monoterpenoid and sesquiterpenoid emissions with profound changes in the emission spectrum. According to correlated patterns of terpenoid emission changes upon stress, highlighted by a hierarchical cluster analysis, candidate terpenoid synthases responsible for observed diversity and complexity of released terpenoid blends were postulated. We conclude that flower volatile emissions differ quantitatively and qualitatively from leaf emissions, and overall contribute importantly to O. basilicum flavor, especially under stress conditions.