What is pollenkitt?
Pollenkitt is a sticky covering found on the surface of pollen grains. It is also spelled “pollen kit” or “pollenkit” and is sometimes called “pollen coat.” It is found in some plant families more often than others, but it is especially common in plants that are pollinated by insects. Because of this, scientists believe that one of the major functions of pollenkitt is to help the pollen stick to the bugs.
Honey bees have special body parts where they pack pollen to be carried back to the hive. The parts—one on each hind leg—are called corbiculae or “pollen baskets.” The corbiculae are covered with hairs which help to hold the pollen in place, but very sticky pollen can form large clumps—something that makes provisioning even easier.
Other bee species carry pollen in hairy receptacles called scopae which may be found on the legs, the underside of the abdomen, or on the back of the thorax. All of these structures are better able to collect and carry pollen that is sticky, rather than pollen that is dry and fluffy.
Not all pollen is sticky
The pollen from many wind pollinated plants, such as grass, is much drier and not nearly so sticky. Dry pollen has to be carried in smaller clumps. When they are carrying smaller loads, the bees have to make more trips to collect an equal amount of pollen. This wastes both time and energy.
Plants that are insect pollinated not only have sticky pollen, they have lots of pollen. This provides the win-win relationship that defines plant-pollinator mutualisms. In this case, the plant has to expend lots of energy to produce excess pollen with sticky coatings to attract the bees. In turn the plant gets pollinated. The bees benefit from lots of pollen that is easy to carry home. In addition, pollenkitt contains lipids, proteins, and phenolic compounds which are important to honey bee health.
Bees carry pollen in multiple ways
It is interesting to note that, in honey bees and bumble bees, the pollen in the corbiculae is not the pollen that is transferred to other flowers for pollination. The pollen that does that job is the pollen that sticks to the body of the bee and rubs off when she visits the next flower. But pollenkitt facilitates this transfer as well: the pollen sticks to the bee until she rubs up against another flower, and then the pollen sticks there instead.
Researchers have suggested many other reasons for pollenkitt and, in truth, it probably has multiple functions. It may keep the pollen from blowing away or drying out, or it may protect the pollen from ultra-violet radiation and certain pathogens.
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