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Question Video: Recalling How Pollen Grains Are Caught by a Floral Structure Science

What structure within a flower is usually sticky to “catch” grains of pollen?

02:25

Video Transcript

What structure within a flower is usually sticky to catch grains of pollen?

A flower is a structure that contains the reproductive organs of certain plants, called flowering plants. This diagram is of a bisexual flower, which contains both male and female reproductive organs. The male organ of a flower is called the stamen. Each stamen consists of a stalk-like filament that supports bulbs called anthers, which produce pollen grains. The female organ is called the carpel or pistil. It contains a stigma, a style, and an ovary. Inside the ovary are structures called ovules.

The diagram here shows four stamens and eight ovules. But the number of both of these structures varies between plant species. An extreme case of this is found in the giant saguaro cactus, whose flowers can have over 3,000 stamens. For flowering plants to produce seeds, they must undergo sexual reproduction. You may remember that sexual reproduction requires the fusion of male and female gametes. In the case of flowering plants, the male gametes, or sperm, are contained in pollen grains. The female gametes, called ova, or ovum in the singular, are found in the ovules. So, how does a plant sperm actually reach an ovum?

Well, this occurs through the process of pollination. During pollination, nectar-feeding animals, such as the bee drawn here, pick up pollen grains from the anthers. This is represented by the small red dots on the bee’s legs and abdomen. Wind can also move pollen. If the animals brush against the stigma or the wind blows pollen in the right direction, the pollen will be deposited on the stigma. The sperm within the pollen grains can then travel down to an ovule to fuse with the ovum.

You might be wondering why the pollen doesn’t just blow off the stigma the same way it can blow off of an anther. Well, the cells of the stigma often secrete a special sticky substance, which ensures that any pollen grains that land on the stigma will stay put, allowing pollination to occur.

Now we have the information we need to answer our question. The structure within a flower that is usually sticky to catch grains of pollen is the stigma.

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