Plant Story of the Month - The Tomato & the Bumblebee
Did you know that bumblebees pollinate many crops that cannot be pollinated by honeybees? Did you also know that tomatoes and bumblebees go hand in hand? Although tomato plants are self-fertile, the flowers must be vibrated by wind, vegetable growers, or bees to release pollen for fertilization. In fact, tomato plant flowers need to be shaken by bumblebees to release protein rich pollen. The “shaking” is oddly done by sound – sound that is generated by the buzzing of bumble bees – it’s called “buzz pollination” or “sonication”. When a bumblebee lands on a tomato flower, it clamps itself to the flower and flexes its wing muscles at a middle-C buzz which dislodges the pollen. Buzz pollinated flowers hide pollen grains deep inside the anthers. A bumble bee will come along and bite down on the base of the anther and violently vibrate it until pollen grains shoot out of the top and cover the bee. The bumblebee then grooms itself to comb the pollen grains down and mixes saliva with it to store easily in pollen sacs on her legs. Not only does this accomplish pollination but it often also accomplishes cross-pollination. Most commercial growers employ bumblebees to perform this service! Korean researchers took this phenomenon a bit further and to several tomatoes, played a loud, high C sound for 6 hours. The effect was that ripening was delayed by about 6 days. This means that sound vibration affects the way the fruit manufactures its ripening hormones. Clearly bumblebees have figured this all out and thus provide the perfect note, in just the right pitch and for the right amount of time to properly signal the fruit of a tomato plant to ripen. They do it so well in fact that they can pollinate over 10 million tomato flowers in a 30-acre greenhouse! Tomatoes are not the only plants that gets buzz pollinated, potatoes, eggplants, blueberries, cranberries, and peppers reply on it as well. Honeybees simply can’t do what bumble bees can. Honeybees can’t pollinate tomatoes because they can’t get the pollen and the flowers do not produce nectar therefore, there is no reward involved. Buzz pollination is an evolutionary strategy still puzzling to scientists. One biologist characterizes it this way, “The flower is almost like playing hard to get….. It’s intriguing, because these buzz-pollinated plants ask for a huge energy investment from the bees, but don’t give much back.” Buzz pollination occurs in about 22,000 flowering plants, many of them unrelated. And previous research has shown that the harder the bumblebees buzz, the more pollen they obtain. So, the next time you are in your garden, watch for bumblebees buzz-pollinating some of your veggies – you might just catch them in action!