Dioecism | reproduction | Britannica (original) (raw)

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• animal and plant systems differentiated
  • 
    In plant reproductive system: Angiosperms
    poplars, and mulberries, which are dioecious. In common parlance (and unfortunately in some botanical textbooks), staminate flowers and plants that bear them are often designated “male,” and pistillate flowers and the plants that bear them are called “female.” This may be traced back at least as far as to the…
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• fungi
  • 
    In fungus: Sexual reproduction
    Such species are termed dioecious. Dioecious species usually produce sex organs only in the presence of an individual of the opposite sex.
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animal systems

• Hydra
  • In reproductive behaviour: Coelenterates
    Hydras are also dioecious; that is, each individual produces either sperm or eggs. In many temperate-zone species of Hydra, sexual reproduction occurs during the autumn; the fertilized eggs enable the species to survive the winter.
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• sponge
  • 
    In animal reproductive system: Gonads, associated structures, and products
    In dioecious species, the sexes are separate. Generally, the male gonads ripen first in hermaphroditic animals (protandry); this tends to ensure cross-fertilization. Self-fertilization is normal, however, in many species, and some species undergo sex reversal.
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• vertebrates
  • In reproduction: Reproduction of organisms
    …all vertebrates, are unisexual (dioecious): the male and female gametes are produced by separate individuals.
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plant systems

angiosperms

• 
  In angiosperm: General features
  …flowers are on another are dioecious, from the Greek for “two houses.”
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• flowers

  • 
    In flower: Form and types
    …different plants, the plant is dioecious (e.g., date, holly, cottonwood, willow); when there are male, female, and bisexual flowers on the same plant, the plant is termed polygamous.
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• papaya

  • 
    In papaya: Physical description
    Normally, the species is dioecious, male and female flowers being produced on separate plants, but hermaphroditic forms are known, and numerous irregularities in the distribution of the sexes are common. Male flowers are borne in clusters on stalks 90 cm long; the flowers are funnel-shaped, about 2.5 mm (0.1…
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• Sapindales

  • 
    In Sapindales: Characteristic morphological features
    This culminates in dioecism, a condition where male and female flowers in the species are borne on separate plants. Dioecism has evolved independently in most families. Many members of the order have bisexual and unisexual flowers on the same plant (polygamous). In some inflorescences, for example, the terminal…
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• definition of unisexuality

  • In unisexuality
    …this condition is often called dioecism. A unisexual species is one in which all individuals are of the same sex. Some species of whiptail lizards, for example, are only female. New individuals grow from eggs that develop without fertilization (parthenogenesis).
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• gymnosperms

  • 
    In gymnosperm: Ginkgophyta
    Like the cycads, Ginkgo is dioecious and bears microsporangia and megasporangia on separate trees. A Ginkgo microstrobilus is borne on a dwarf shoot among the fan-shaped leaves. The microstrobilar axis bears stalked appendages at the ends of each of which are two microsporangia. Megastrobili are borne on elongated slender stalks,…
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• pollination and breeding methods

  • 
    In plant breeding: Mating systems
    …in the carrot and walnut), dioecy (male and female parts are borne on different plants, as in the date palm, asparagus, and hops), and genetically determined self-incompatibility (inability of pollen to grow on the stigma of the same plant, as in white clover, cabbage, and many other species).
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• willow and date palm

  • 
    In pollination: Structural
    …and willows (Salix species)—have become dioecious; that is, some plants produce only “male” (staminate) flowers, with the rest producing only “female” (pistillate or ovule-producing) ones. In species in which staminate and pistillate flowers are found on the same individual (monoecious plants) and in those with hermaphroditic flowers (flowers possessing both…
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