There are two ways in which new plants are made: sexual propagation and asexual propagation. Sexual propagation consists of the combination of egg and pollen to form a seed. Whereas, asexual propagation is a clonal way to create new plants that does not utilize the reproductive parts of flowers. Not all new plants can be created successfully the same way, so it important to understand how different plants reproduce.
To give you an idea of how sexual propagation works, there are a few things you need to know beforehand.
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Perfect Flowers versus Imperfect Flowers
There are two different types of flowers: perfect and imperfect (also known as complete and incomplete). Perfect flowers contain both male and female reproductive parts, while imperfect flowers either contain only female reproductive parts or only male reproductive parts. This is important to know because in sexual propagation, the male parts need to fertilize the female parts.
Monoecious Plants versus Dioecious Plants
There are two types of plants: monoecious and dioecious. Monoecious plants have both male and female reproductive parts on the same plant. Monoecious plants can have perfect flowers, where the male and female reproductive parts are included in the same flower or imperfect flowers, where the male and female flowers occur separately throughout the plant. Dioecious plants have only male or female flowers on each plant. With dioecious plants, you will never find both male and female reproductive parts on the same plant.
Why is this important? Because all this determines how easy it is for a female flower to get pollinated.
Cross-Pollination versus Self-Pollination
The two types of sexual propagation are self-pollination and cross-pollination. This idea entails whether the flowers on the same plant fertilize themselves or if another plant’s involvement is necessary and the plant needs to cross-pollinate in order for the fertilization process to be successful.
- Self-pollination – Self-pollination can only take place in monoecious species, where there are both male and female plant parts on the same plant. However, although a species may be monoecious, that does not mean that the plants will be self-pollinated. Walnuts are a great example of this. Walnuts are monoecious species, but the female flowers do not open at the same time as when the male flowers release the pollen, so it is impossible to be self-pollinated. A way to combat this problem is to strategically plant different cultivars/varieties throughout an orchard to make sure the female flowers are pollinated by the desired male pollen that has the same season as those female flowers.
- Cross-pollination – Cross-pollination occurs with both monoecious and dioecious species. In any case, flowers on one plant are being pollinated by pollen on another plant.
Insect Pollination versus Wind Pollination
Plants are also predisposed to prefer either wind versus insect (e.g., bees, insects, butterflies) pollination. The basic indicator for this is whether or not the plant has showy flowers. The flowers are meant to attract insects for pollination. Some common examples include fruit trees in bloom, strawberry flowers and your everyday ornamental flowers.
If adapted to be wind pollinated, the female flowers do not have any petals, no nectaries and the female portion of the flower (stigma) is exerted. For male flowers, they also do not have any petals, the male portion of the flower (anther) is exerted and the pollen is lightweight so that it can be easily carried by the wind. If you have a dark car, you might have noticed when the pollen transfer is happening with the trees around you!
If you are interested in learning more about plant propagation, click here to learn all about asexual propagation!
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