Citronellol: geraniol ratios and temperature in geranium (Pelargonium hybrid)

SummaryConcentrations of citronellol and geraniol in essential oil from rose geranium (Pelargonium hybrid) were monitored monthly over four years using gas chromatography-mass spectrometry. Geraniol concentrations fell in winter and citronellol concentrations increased in spring. The citronellol/geraniol (C:G) ratio was a more sensitive indicator of change in oil composition than the concentration of either alcohol in isolation. C:G ratios rose sharply if the minimum air temperature (Tmin) fell below 5.58C for any time during the 5 d prior to monthly harvesting. A nonlinear model is proposed to predict the C:G ratio at any Tmin. High C:G ratios indicated cold stress in geranium plants.