Chasing Plant Fragrances
ANUPAMA
People often ask me, “Why go through all the trouble of collecting floral scents directly from the field? Can’t you just pluck the flowers, boil them, and extract the essence?” Well, sure, I could do that—but it would only give me a chemical snapshot of the flowers, not the story behind the fragrance. Getting at this story would involve answering questions such as how different are each plant species in terms of their release of scents during day and night?, do they exhibit any difference, either in the number of the fragrance compounds that they release or their concentrations?
You might be wondering how I collect fragrance without plucking the flowers. Well, this method is called headspace sampling, where you wrap the whole bunch of flowers or inflorescence with an inert transparent oven bag while still being attached to the plant. We use two airflow pumps at standardised rates to pump air in and out of the bag., setting up a headspace of volatile fragrance compounds within the bag. After allowing the setup to run for a specified duration, a trap attached to the pump pulls the air out of the setup, and the fragrance compounds are also adsorbed into it which is later extracted into an organic solvent.
Image reference: Practical approaches to plant volatile analysis, 2006
Illustration by Ipshita
Voilà! I’ve collected the fragrance without ever plucking a single flower! This is the best method to obtain the true profile of fragrance compounds that plants emit in natural conditions.
But that won’t still tell me who the plants want to attract! They aren’t spending their precious energy to make us “humans” happy. These scents are for the tiny insects, birds, and other pollinators that visit them. But the plants too make use of their visits. It’s a trade-off: the pollinators get a meal (nectar or pollen), and the plants get their pollen transferred to other flowers, ensuring their survival and reproduction. Plants are chemists and as Micheal Pollan beautifully put it in the Botany of desire “Plants are nature’s alchemists, expert at transforming water, soil, and sunlight into an array of precious substances, many of them beyond the ability of humans to conceive, much less manufacture. While we are nailing down consciousness and learning to walk on two feet, they were by the same process of natural selection, inventing processes and investing their energies on making complex molecules.”
Along with other floral traits such as color and shape, scents attract pollinators from long distances. When animals visit the flowers to collect rewards like nectar or pollen, the plant ensures that its pollen grains attach to the animals' bodies. In this way, the animals act as vectors, transferring the pollen either to a different individual of the same plant species or to a related plant. Therefore, floral fragrances are their way of saying, “Hey, over here!” to pollinators, ensuring their fitness and survival.
This was just a glimpse of my first fieldwork experience. Over the years, I’ve figured out ways to make scent collection less tedious, but I’ll never forget that initial adventure. Fieldwork always starts with excitement and optimism—you dream of finding your plants, setting up experiments, and collecting pristine data. But for field ecologists like me, reality often has other plans. My work isn’t as simple as collecting whatever I find. Sure, I might spot my plants near roadsides, but I often need samples from what we call ‘pristine’ habitats, far away from air pollutants. My collection traps, though, are too generous—to the point that they’ll grab whatever’s in the air, good or bad.
The entire 2-3 months of the time I typically spend on the field hinge on hope—the hope that I’ve collected all the right scents. And the verdict? I only get that back in the lab. When I see peaks on the chromatogram, it’s like looking at the ECG of a healthy person. Relief washes over me. But if there are no peaks? BAM! It’s back to waiting for the next field season, when my plants decide to flower again.
The machine (Gas chromatography-mass spectrometry) tells me the verdict of my collection hates water. So I need to be extremely careful in the field to avoid water in my samples.
My samples are my babies, and I’m fiercely protective of them. Fieldwork isn’t just science—it’s an adventure, a test of patience, and a dance with nature. And every time I step into the field, I’m reminded why I fell in love with this work in the first place.
As Barbara McClintock said, "I know my [samples] intimately, and I find it a great pleasure to know them."
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References
Curious about how we collect fragrances, without plucking a flower? Check out these articles:
About Anupama
Anupama is a final-year PhD student at the Tropical Ecology and Evolution lab at IISER Bhopal, where she dives into the fascinating world of floral fragrances of wild tropical gingers. During free hours, you’ll likely find her singing, painting, or capturing the beauty of the world through her camera.
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Chasing Plant Fragrances
ANUPAMA
"People often ask me, “Why go through all the trouble of collecting floral scents directly from the field? Can’t you just pluck the flowers, boil them, and extract the essence?” Well, sure, I could do that—but it would only give me a chemical snapshot of the flowers, but not the story behind the fragrance."
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