This flower blasts citrus scent only at dawn for bees
Mayorquin AZ, Paiva EAS, Dötterl S, Oliveira R, Vidal DM, Schlindwein C.
Plant Signaling
If you've ever wondered why some flowers in your garden seem fragrant one moment and scentless the next, this shows scent isn't a constant background hum but a precisely timed broadcast tuned to when specific pollinators are actually flying.
A passionflower called Passiflora pohlii opens its blooms right at dawn and releases a strong citrus smell from tiny structures on its petal-like fringes, called osmophores. That scent is aimed squarely at early-morning bees, and within about an hour it drops by 90% as the scent-making cells inside the flower break down, so the whole show is over almost as fast as it started.
Key Findings
Outer corona filaments (the fringe-like structures inside the flower) are the main scent source, packed with osmophore cells
Floral scent emission peaked at dawn and declined by 90% by late anthesis (early morning), even though the flower stayed fully turgid
Scent was dominated by monoterpenoids, mainly geraniol and related 'citronelloid' compounds, and the decline in scent tracked visible degradation of cell organelles under electron microscopy
chevron_right Technical Summary
A tropical passionflower opens at dawn and pumps out a strong citrusy scent for just a few hours, perfectly timed to attract the sleepy-eyed bees that pollinate it before the smell fades away by 90%.
Abstract Preview
Original paper
Scent rhythms in twilight-flowering <i>Passiflora pohlii</i>: osmophore structure and terpenoid volatiles.
Some plants emit floral scents at night and are pollinated by nocturnal bees, yet their scent dynamics, composition, and emitting tissues remain poorly understood. Here, we study <i>Passiflora pohl...
open_in_new Read full abstractAbstract copyright held by the original publisher.
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Passiflora, known also as the passion flowers or passion vines, is a genus of about 550 species of flowering plants, and the type genus of the family Passifloraceae.