Detection of volatile organic compounds in plant stress: a study on geraniol

Thesis

Detection of plant volatile organic compounds as indicators of plant stress can improve crop yield and agricultural sustainability by enabling early-stage treatment of crop stress and by reducing the overall use of agricultural resources. In this work, the feasibility of detecting gaseous geraniol, a plant volatile, using cavity enhanced absorption spectroscopy (CEAS), a sensitive and non-destructive analytical technique, was assessed. For geraniol gas, a limit of detection of 147 ppb was achieved, and a limit of 25.5 ppb was calculated to be attainable with modifications to the experimental setup. For geraniol in solution, gas chromatography–mass spectrometry (GC-MS) measurements were performed, and a detection limit of 2.6 μM was established. Rose (Rosa 'English Princess') petals, pelargonium (Pelargonium 'Attar of Roses') leaves, and genetically modified tobacco (Nicotiana benthamiana) leaves were analysed for their geraniol content. 8.2 μM of geraniol was detected in liquid extracts of 0.5 g of pelargonium leaf and, employing two different assumptions, upper limits of 670 and 1930 ppb were estimated for the concentration of geraniol expected in the headspace of this tissue. For 0.5 g of tobacco leaf, an emission rate of 117 ppb/h was calculated for a 20 mL headspace using data from previous studies. It was concluded that CEAS is a promising technique for sensitive detection of plant volatiles. In addition to geraniol measurements, chemical composition of the rose petals and the pelargonium leaves were analysed by headspace and liquid extract GC-MS measurements. Detected compounds were compared with compounds reported for related species and cultivars. Many of these compounds play key roles in stress signalling in various plants, and their detection could be instrumental in monitoring the health of these plants.

Authors: Cazimoglu, I

• Type of award: MSc by Research
• Level of award: Masters
• Awarding institution: University of Oxford
• Language: English