Role of bees in pollination of plants?

The role of bees in pollination is simply invaluable. It has long been proven by scientists that agricultural lands where there are beekeeping farms have a much higher yield.
Plants such as sunflower, clover, buckwheat, after pollination by bees, give high yields of seeds. This is especially facilitated by weather conditions during flowering. The clear, sunny weather attracts many bees, which collect nectar.
Today, bee labor is even used in greenhouses for pollination of cucumbers. Such greenhouses give incomparably higher yields than those in which pollination is done by hand.