Pollination and fertilization

Pollination is the landing of pollen ripened in the anther on the stigma of the pistil. In cross-pollination pollen travels from the anther of one flower to the stigma of another by insects, wind, water or birds; in many plants pollen and pistil do not ripen at the same time, so a flower cannot pollinate itself. Insect-pollinated flowers (apple, apricot, pear, alfalfa, cotton) are brightly coloured, fragrant and have nectar; insects come for pollen and nectar and carry pollen stuck to their hairs to another flower; the stigma is moist and sticky. This is why beehives are placed in orchards and cotton fields during flowering — it raises yield and honey quality. Wind-pollinated plants (maize, rye, willow, poplar, walnut) have small, plain, scentless flowers with light, abundant pollen; willow, poplar and walnut often bloom before the leaves appear. Wheat, barley and rice are mainly self-pollinated; when their stamens hang out of the ear, the wind also helps. In self-pollination a flower’s pollen lands on its own stigma. People artificially pollinate plants such as maize — to raise yield and to create new varieties.