The anther produces pollen male reproductive cells. The filament holds the anther up. During the process of fertilization , pollen lands on the stigma, a tube grows down the style and enters the ovary. Male reproductive cells travel down the tube and join with the ovule, fertilizing it. There are still a lot of mysteries about how and why some types of outcrossers are dioecious. Scientists decided to look at the DNA from many different kinds of dioecious plants to try to understand what makes them male or female.
There is a lot you can learn from DNA that may not be so obvious from just looking at or growing a plant. A DNA sequence is a lot like letters on a keyboard: the letters by themselves do not mean anything, but when they are put together they can form words. Scientists compared the genes from several dioecious plants to figure out which genes were important in determining whether a plant is male or female. They discovered that there are several ways a plant can determine gender. For example, there can be genes in the DNA that make plants male or genes that prevent them from becoming female [ 1 ].
Looking at plant DNA is not the only way scientists can learn about the differences between male and female plants. For example, they can study the shape differences between male flowers and female flowers. You can do this too! Unlike humans, plants cannot move around. This means that plants need to use other strategies to move pollen to ovules to make seeds. For outcrossers, the male plants do not need to spend their energy making seeds, so they can spend more energy on making and dispersing high-quality pollen.
Similarly, since female plants do not need to make pollen, they can spend more energy on making high-quality ovules. This means that they can pass on more resources to their offspring to improve their chances of survival.
Furthermore, because dioecious plants need two different plants to reproduce, the offspring will have more variety in the genes they get from the parents. This is especially important if the environment changes, because the offspring with greater variety in their genes will be more likely to have genes that help them adapt to a new environment. On the other hand, selfers, whose offspring only have genes from their one parent, would have less variety in their genes and might have more trouble adapting to environmental changes.
This is a pretty great advantage for outcrossers! The growing pollen tubes are guided by chemical signals emitted from the egg cells and tissues within the pistil. The ovary tissues are also involved in preventing sperm with certain genetic mutations from entering. By selecting which sperm cells can pollinate the egg cells, the ovary protects embryos from developing genetic mutations that may lead to infertility.
Different ovary arrangements result in many different types of fruit. Plants that have evolved to use animals to disperse their seeds use fruit — swollen ovaries — as an attractive food source and reward. The fruit plays a vital role in signaling to animals when it is ready to be eaten. Immature fruit tends to be green, hard and bitter tasting.
Once the seed has matured and is ready for dispersal, most fruits turn red, purple or orange and are soft and sweet tasting to lure animals in. This fertilization results in the production of a seed, which can grow into another plant once it finds soil. The ovary of a flower may contain only one ovule, but it usually has more.
Some plants, such as cherries, have only one ovary because these have only a single pistil. The egg structure is formally referred to as a gametophyte, in some species also called an embryo sac. Normally, there are usually eight cells in the gametophyte, including the egg itself; two synergids, one on each side the egg; two polar nuclei in the middle of the embryo sac; and three antipodal cells at the other end of the embryo sac from the egg.
Kevin Beck holds a bachelor's degree in physics with minors in math and chemistry from the University of Vermont. Formerly with ScienceBlogs. More about Kevin and links to his professional work can be found at www. What Is Function of the Pistil in Flowers?
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