Planet Earth

Charged Pollen


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Wind, insects, bats, and birds have been pollinating flowers for millions of years, and to all appearances doing it rather well. Yet Souvik Banerjee thinks he might be able to do better. He has found a way to give pollen grains an electrostatic charge. The charge, says the University of Georgia research engineer, naturally attracts the pollen to plants.

Farmers in the United States, as in other countries, now rely mostly on natural means of pollination. For crops that are not native to a region and that therefore don’t have a large number of natural pollinators available, they often have to rent bees, at high cost. Farmers do occasionally dust pollen on their crops. But the pollen not only goes to the plant, it also goes everywhere else, says Banerjee. It isn’t reliable, there is a lot of waste, and since pollen grains are very small, they tend to remain airborne for a long time and be more of an irritant to people. I’m personally very allergic to pollen, and during the spring I have a terrible time.

Banerjee and Edward Law, an agricultural engineer, may have a better way. They decided to try to apply a small electric charge to pollen. As a charged pollen grain wafted near a flower’s stigma--the female part of the flower--the researchers reasoned that the grain’s tiny electric field would induce an opposite charge in the stigma. If the pollen were positively charged, it would attract electrons to the stigma’s surface; if negatively charged, it would attract protons. In either case, the electrical attraction would help pull the pollen to the stigma.

Pollen turned out to be a poor electrical conductor and was difficult to charge. So Banerjee and Law mixed the pollen with distilled water and some salt. This pollen-water mixture is easily charged and applied: it’s stored inside a tank and pumped through a hollow electrode. A high-speed airstream turns the mix into a fine spray.

In lab tests, the researchers sprayed their mix on plants that were isolated from natural pollinators. In another part of the lab they sprayed uncharged pollen on a control group of plants. The charged mix deposited nearly five times as much pollen on the plants as did spraying with uncharged pollen.

The only field test to date has been in a California almond grove. Unfortunately, a heavy rain the day after the test washed away the pollen--and the test results. Worse, the trees came down with a fungal infection unrelated to the spraying. But Banerjee and Law plan to repeat the test early next year. We have seen from the lab studies that there is a tremendous amount of increase in pollen deposition, says Banerjee, so we don’t have any basis to think this wouldn’t work.

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