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Pollination

Pollination enables a plant to reproduce itself by producing seeds. It involves the transfer of pollen from the anthers (male organs) of one flower to the stigma (female organ) of another of the same species.

Flowers produce nectar to attract bees and other insects (and animals) to pollinate them. As a bee collects nectar, pollen collects on her hairy body. Her flower fidelity means she visits flowers of the same species and inadvertently pollinates them at the same time.

Most insect-pollinated flowers can be pollinated by a variety of insects. White clover, for example, is pollinated by honeybees, bumblebees and solitary bees. Others rely on only one sort of insect: for example, cocoa flowers are pollinated only by midges. Certain plants are pollinated by other animals (such as birds and bats); wind (for example, cereals, other grasses, most conifers and many deciduous trees); or humans (for example, greenhouse melons). And certain crops, including broad beans and coffee beans, can self-pollinate.

However, honeybees are the main pollinators of many plants, including many crops (such as almonds, apples, avocados, blueberries, cherries, cranberries, lettuce, oilseed rape and sunflowers). In 2011, a United Nations Environment Programme report noted that bees help pollinate more than 70 per cent of those 100 crops that supply 90 per cent of the world's food. In countries with a temperate climate, about a third of vegetable, fruit and nut crops, plus most wild flowers, depend on bee pollination.

A lack of bees limits the harvest from bee-pollinated crops. Some such crops, including almonds and blueberries, can crop without pollination, but this delays ripening; encourages damage by disease, poor weather, pests and pesticides; and produces fewer, smaller or seedless fruits.

All this has led to the vast industry of migratory beekeeping. Farmers pay beekeepers to transport bees sometimes thousands of miles to pollinate crops such as almonds, apples, blueberries, borage, field beans and oilseed rape. In the US, more than 2.5 million hives are rented to farms each year. One million, for example, go to almond orchards in California; 50,000 to blueberry fields in Maine; and 30,000 to apple orchards in New York State.

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