Most flowering plants contain both male and female flower parts. Sometimes, these organs are found in the same flower, while other plants grow separate male and female flowers. With close observation, you can typically identify a flower’s reproductive organs and identify the sex of the flower.
Monoecious and Dioecious Plants
When a plant has both female and male flowers on the same plant, it’s called amonoecious plant.Often, these flowers will mature at different times to prevent self-pollination. This kind of plant is sometimes called the “perfect plant.” On this plant, you can find both complete and incomplete flowers.
Garden vegetables such as corn (Zea spp.) and squash (Cucurbita spp.) are monoecious, as well as some evergreens, such as pines (Pinus spp.) and cedars (Cedrus spp.). Several nut-bearing trees, such as chestnuts (Castanea spp.) and hazelnuts (Corylus spp.) are monoecious as well.
Dioecious plants are those in which male and female flowers are present on separate plants. A male and female plant must be present for pollination to occur. For these plants, it is physically impossible to self-pollinate, so genetic diversity is guaranteed.
Some edible fruits, such as mulberries (Morus spp.), kiwi (Actinidia spp.) and persimmons (Diospyros spp.) are dioecious. Evergreens can be dioecious, like hollies (Ilex spp.) and junipers (Juniperus spp.). Several shade trees are dioecious, such as the maples (Acer spp.) and honeylocusts (Gleditsia spp.).
Flowers are arranged in different ways. Perfect flowers or Complete flowers contain both male and female organs. Examples of plants with these types of flowers are peppers and tomatoes. Imperfect flowers or incomplete flowers have just male or female parts, such as many types of squash. In other words, a complete flower comprises all four flower parts, including the petals, sepals, stamen and pistil. Perfect flowers are often complete flowers, but some may be missing petals or sepals, making them incomplete flowers.
In monoecious plants, male and female imperfect flowers are on different parts of the same plant, while in dioecious plants, they are on separate plants. Regardless, the male sex cells or sperm — are contained within pollen and located on the anther of the flower. In flowers whose male and female organs are in the same bloom, these are the long, narrow stalks surrounding the main, thicker stalk within a flower. This thicker stalk is called the pistil. It contains the female sex organs in perfect and imperfect flowers and must receive pollen for fertilization to occur.
The pistil contains three main structures: the stigma, which is located at the top and receives pollen, and hence sperm; the style, which is the long stalk that transports the pollen downward to fertilize the ovule; and the ovary, which contains the ovule that in turn contains the egg. This egg is analogous to the egg that humans and other female animals possess in that it contains half of the reproductive information needed to form a new plant.
With dichogamous plants, the pistils and stamens (reproductive parts) are in the same flower but mature at different times. Almost all plants in the daisy family (Compositae) and the carrot family (Umbelliferae) are dichogamous, and include plants such as sunflowers (Helianthis spp.) asters (Aster spp.), parsley (Petroselinum spp.) and celery (Apium spp.), Pecan trees (Carya spp.) are also dichogamous.
Process of Pollination
Both monoecious and dioecious plants normally need to be cross-pollinated. A pollen grain will land on a receiving stigma and travel down the pollen tube to the ovary. The genetic material of the male fertilizes the ovule. These turn into seeds, which results in a pollinated calyx. The ovary surrounding it grows into a fruit.
Monoecious vs Dioecious Plants
|A monoecious plant is one that has male and female flowers on the same plant.||Dioecious plants are plants that have both male and female flowers on different plants.|
|Monoecious produce both male and female gametes by the same plant.||Dioecious produce male and female gametes in separate plants.|
|Monoecious plants are capable of both self and cross pollination.||Dioecious plants are only capable of cross pollination.|
|Squash, corn, walnut, oak and hazel are common monoecious plants.||Marijuana, Asparagus, Ginkgo biloba trees, Papaya, willow, holly, and poplar are dioecious plants.|
|Presence of Unisexual flowers on the same plant.||Presence of Unisexual flowers on different plant.|
|All plants are capable of seed production as there is female flowers.||Seeds are produced in female plant only. That is only 50% of the individuals in populations contribute to seed production|
|Low genetic variation and increased homozygosity due to self pollination or inbreeding.||High genetic variation and increased heterozygosity due to cross pollination.|
|Monoecious are capable of reproducing even when they are isolated.||Dioecious are incapable of reproducing when they are isolated.|
|Monoecious exhibit uniparental reproduction.||Dioecious exhibit biparental reproduction.|
|Comparatively less efficient pollinating mechanisms as self pollination is common.||Efficient pollinating mechanisms such as more flower production, large fleshy fruits etc and with different pollinating agents including insects, birds etc.|