How are plants pollinated?
Why does understanding how plants are pollinated matter to a seed saver?
There are perfect flowers and imperfect flowers.
1. Perfect flowers have the male and female parts in the same flower. Some perfect flowers are self-pollinated, which means the male part fertilizes the female in the same flower. Others cross-pollinate, which means pollen from another flower. The pollen can come from a flower on the same plant or a different plant, but the plant needs to be the same species. For example, only a cosmos flower can pollinate and fertilize a cosmos flower.
Examples of plants with perfect flowers that self-pollinate are tomatoes, peas and beans. Broccoli and cauliflower are perfect flowers, but they tend to be self-incompatible, which means they do not accept their own pollen and need to cross-pollinate.
2. Imperfect flowers have separate male and female flowers. A common example are plants in the cucurbit family. Cucurbits include cucumbers, squash and melons. If you've ever grown squash, some of the female blossoms shrivel and die. That is because the female was not fertilized Some people like to cook squash blossoms. They eat the male flowers because if they ate the females they would not get the fruit.
Flowering plants are classified as angiosperms. Angiosperms co-evolved with other organisms, such as insects and birds, to increase the plant's ability to reproduce. Sometimes the plant provides food or shelter to the animal in exchange for pollination services.
Pollination happens usually by animal, wind or self:
1. Wind pollination occurs in about 20% of angiosperms. The wind can carry pollen a long distance. Many members of the grass family are wind pollinated. Corn, a member of the grass family, is wind pollinated and is very difficult to save properly in the home garden if other people in the neighborhood are growing it. Corn has imperfect flowers. The male tassels are on top and the female silks are attached to a kernel on the cob. It is difficult to save because wind can carry pollen a long distance and if you want to save seeds from corn a distance of 800-1/2 mile from other corn varieties is needed. There some advanced seed saving techniques where plants are bags and hand-pollinated, but this takes a lot of time. Additionally, to ensure quality corn seed a minimum population of 200 plants need to be grown!
2. Animal Pollinated - Mostly Insects
Flowers are often pollinated by insects, but bats, birds and even humans sometimes pollinate flowers. Bees are attracted to flowers because they get pollen and nectar as major food sources. Nectar is a sweet, sugary liquid that flowers of many angiosperms produce to attract animal pollinators. When animals pollinate flowers, both organisms benefit. The flowers get pollen transferred and the insects or other animals get food.
Although bees are not the only things that pollinate flowers, about 1/3 of the food that humans eat depends on pollination by bees. In the last 50 years, there has been a huge loss of honey bee colonies that has been called Colony Collapse Disorder.
Some common crops that are pollinated by insects are sunflowers, squash and broccoli. In order to save these crops cross pollination from other varieties needs to be prevented. Squash is hand pollinated whereas in broccoli cages are places around the plants allowing the insects inside the cages to pollinate while excluding insects from other plants with other pollen to enter.The night before flowers open male and female flowers are taped shut. Then the following morning, before the insects awake, the male is removed and used like a paintbrush to pollinate the female. Then she is closed back up.
Some flowers accept their own pollen. This happens with some perfect flowers. Remember that perfect flowers have the male and female parts in the same flower. This type of pollination is called self-pollination. Beans and peas are extremely self-pollinating meaning that the pollen and ovule are from the same flower. This makes them super easy to save the seeds properly and the seeds will come true-to-type, which means they will look like the parent plant.