Seasonal and diel variations in scent composition of ephemeral Murraya paniculata (Linn.) Jack flowers are contributed by separate volatile components

Scent profile of the ephemeral nocturnal floral species Murraya paniculata was characterized to assess diel and seasonal variability. The floral fragrance was found to constitute a characteristic set of 15 major volatile organic compounds (VOCs) dominated by benzenoids, terpenoids and phenylethanoids. Strong diel variability was detected due to dominantly endogenous regulation of 2-phenylethanol and (E)-β-ocimene emission levels, along with temperature-correlated emission rates of 2-phenylethanal, methyl benzoate, methyl anthranilate and germacrene D, resulting in high diurnal contents of the former two VOCs and high nocturnal contents of the latter four VOCs in the fragrance. Significant seasonal variation was contributed by a separate suite of VOCs including linalool, nonanal, decanal, methyl salicylate and methyl palmitate. Higher abundances of these components in certain seasons were found to add subtle variations in the strong diurnal/nocturnal division in the scent profile. Emission rate of linalool is endogenously regulated on a seasonal scale, but that of (E,E)-α-farnesene was maintained at consistent proportions even if correlated to temperature variations. It was concluded that the two sub-sets of major scent compounds, each comprising six VOCs, are adaptive responses such that the strong day/night component of variation in maintained along with necessary physiological adjustments to changing seasons. The varying effects of climatic factors on the 15 major VOCs indicated different regulating mechanisms comprising environmental and endogenous mechanisms in different degrees.