Flowers come in a dazzling array of colors and emit lovely fragrances. But why have flowers evolved these traits? The bright colors and sweet scents of flowers actually serve important biological functions.
Attracting Pollinators
One of the primary reasons flowers have bright colors and pleasant smells is to attract pollinators. Pollinators, such as bees, butterflies, and hummingbirds, transfer pollen from one flower to another which allows the plants to reproduce. The brighter and more vivid the flower, the more likely it will catch the eye of pollinators. Fragrances serve a similar function by luring pollinators close to the reproductive parts of the flowers.
Different pollinators are attracted to different colors and scents. Bees cannot see the color red, but can see ultraviolet light patterns on flowers that signal where nectar can be found. Butterflies rely more on sight and are draw to warm colors like yellow, orange and red. Nocturnal pollinators like moths are lured in by pale or white flowers that are visible at night. The type of scent produced by a flower also targets specific pollinators. For example, flowers pollinated by flies or beetles emit aromas of rotting flesh!
| Pollinator | Flower Color Preferences | Flower Scent Preferences |
|---|---|---|
| Bees | Blues, purples, yellows | Sweet, fresh, floral |
| Butterflies | Red, orange, yellow | Fruity, rose, vanilla |
| Moths | Pale, white | Heavy, sweet |
| Flies | Brown, purple, red | Foul, fetid |
As shown in the table above, flowers have evolved specific color and odor combinations designed to appeal to certain pollinating creatures.
Signaling Ripeness
Another reason for bright flower colors and scents is to signal ripeness. Many flowers change color or emit stronger fragrances when they are at peak fertility. This visual and olfactory advertisement helps pollinators recognize which flowers are ready for pollination.
One example is lilies. Many lily species are white when in bud and turn vivid colors like yellow, pink or red upon blooming. This color change indicates the flower is now mature and ready to receive pollen. Lilies also intensify their floral sweet perfume as the flower opens up fully. This dual color and scent change serves as a reliable readiness indicator for pollinators.
Attracting Seed Dispersers
After flowers are pollinated, they develop into fruits containing seeds. Ripe fruits often use bright colors and distinctive scents to signal they are ready to be eaten. By attracting animals like birds and mammals to eat the fruit, the seeds get dispersed through defecation or regurgitation.
Some examples of ripe fruits that change color include bananas turning yellow, cherries becoming red, and blackberries darkening from red to black. These color changes indicate ripeness and nutrient richness to fruit eating animals. Many ripe fruits also emit strong, sweet fragrances. The aroma helps foraging animals locate the fruits among all the surrounding foliage.
Repelling Herbivores
While flowers and fruits want to attract pollinators and seed dispersers, they want to deter herbivores that would eat their leaves, stems, or unripe reproductive parts. Some plants have evolved chemical defenses using bright colors and scents to signal toxicity or unpleasant taste to herbivorous animals.
A classic example is poison dart frogs which are vibrantly colored to warn predators of their extreme toxicity. Some insect pollinated flowers also produce a smell of rotting meat to repel nibbling animals while still attracting specific flies or beetles. Prickly, foul smelling leaves or thorns on plants also function to repel grazing by mammals.
Communication Between Plants
Research has found that scent and volatile compounds produced by flowers and plants can also facilitate communication between neighboring vegetation. Plants release chemicals that can relay information about herbivore attacks. This allows surrounding plants to preemptively activate defenses. Flower scents might also provide cues on optimal times for neighbor plants to bloom.
Conclusion
In summary, flowers and plants have evolved brightly colored petals and strong fragrances for several biological reasons:
- To attract, guide, and reward animal pollinators
- To signal ripeness of reproductive parts to pollinators
- To attract seed dispersing animals like birds and mammals
- To repel plant-eating herbivores
- To communicate with neighboring plants
Next time you admire colorful blooms like daffodils, tulips, roses or orchids, or breathe in the lovely scent of jasmine, gardenias or lavender, remember that those traits serve critical functions for the plant’s reproductive success and survival.
