A study has shown that the caffeine-laced nectar of some plants improves the learning process for bees by enhancing their memory.  As a result, the bees are more likely to keep returning to pollinate the flowers providing caffeine.
In effect, these plants use caffeine to alter the pollinating bees’ behavior, said Geraldine Wright, a honeybee brain specialist at Newcastle University in England, who, with her colleagues, reported these findings in Science this week.

Bee and Coffee Blossom

Flowers demonstrating this effect include coffee plant blossoms.  According to researchers, the nectar from these blossoms delivers about as much caffeine concentration as a cup of instant coffee.  In addition, we are now being told that the nectar of orange and grapefruit blossoms is also a source of caffeine, although in lower concentrations.  Supposedly, these researchers discovered that, as a result of caffeinated pollination, some kinds of honey contain caffeine as well.
Caffeine helps bees remember that the flower’s scent will give them what they are looking for, so the bees will seek out the caffeinated flowers, and, as a result, will transfer their pollen.

How did researchers determine that caffeine improves a bee’s memory? The scientists trained individual bees to expect a sugary drink when they smelled a certain floral scent.  Some bees received nectar-like concentrations of caffeine in their drink, while others did not.  After a day or two passed, the bees were exposed to the same scent and researchers watched to see if they extended their feeding tubes in response, a sign they were ready to sip.  Incredibly, after 24 hours, three times as many bees remembered the connection between odor and reward if the reward contained caffeine.  Researchers then tested the effect of caffeine on neurons in the bee brain and found that its action could lead to more sensitivity in neurons called “Kenyon cells” that are involved in learning and memory.

The amount of caffeine occurring in the leaves of many plants is toxic to insects, and, in fact, caffeine is used by plants to ward off predatory insects and microbes.  But the lower concentration found in nectar attracts some insects and boosts their memories by affecting certain brain cells.

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