Abstract
Oil palm plantations are rapidly expanding in the tropics because of insatiable global demand for fruit oil to be used in food, biofuels and cosmetics. Here we show that three tissue-specific volatiles can be quantified in ambient air above an African-American hybrid oil palm plantation in Brazil and linked photosynthesis (isoprene), floral scent (estragole), and for the first time, fruit oil processing (6-methyl-5-hepten-2-one, MHO). Plant enclosure techniques verified their tissue specific emission sources with ambient concentrations displaying distinct diurnal patterns above the canopy. Isoprene concentrations were near zero at night, but dramatically increased during the day while estragole showed elevated concentrations at night suggesting a light-independent, temperature-driven emission pattern from flowers. MHO also showed elevated concentrations at night and both estragole and MHO increased during the day. Our observations demonstrate that the African-American oil palm hybrid is strong isoprene emitter and suggest that MHO is a specific oxidation product of lycopene released during the industrial processing of palm oil. This study highlights the potential value of quantifying volatile oil palm signals in the atmosphere as a novel, non-invasive method to better understand biological functioning and its interactions with the environment including carbon assimilation, floral-insect interactions, and fruit oil production/processing.
Highlights
Oil palm is cultivated in the tropics as a major global source of healthful and low-cost vegetable oil for use in food additives and as a cooking oil with its widespread use in a multitude of food products increasingly consumed around the world.[1]
The occurrence of isoprene emissions from tropical leaves has been previously described as mainly deriving from carbon and energy resources from photosynthesis through a direct utilization of photosynthetic products by the 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway; the isoprene formation pathway that occurs within the thylakoid membranes of chloroplasts located inside the mesophyll cells of leaves.[13,14]
The gas chromatography-mass spectrometry (GC-MS) chromatogram obtained from the glass chamber with a leaf inside shows a strong peak for this compound occurring with a retention time of 7.2 min (Figure 2)
Summary
Oil palm is cultivated in the tropics as a major global source of healthful and low-cost vegetable oil for use in food additives and as a cooking oil with its widespread use in a multitude of food products increasingly consumed around the world.[1]. To verify the identity of different VOC sources within the oil palm plantation, we used manual collections of air samples on thermal desorption tubes from plant enclosures on the ground to identify tissue-specific VOC emissions from leaves, flowers, and fruits, including the first report of atmospheric 6-methyl5-hepten-2-one (MHO) as a volatile biomarker of lycopene oxidation, possibly during fruit oil processing.
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