|MadSci Network: Botany|
In most flowering plants, or Angiosperms, each flower contains both male and female parts: the male parts are the stamen with pollen-producing anthers at the end of long filaments; an d the female parts are the pistils, each with a stigma for collecting pollen at the end of a style attached to the ovaries. Most of the familiar garden and wild flowers have both male and female parts, so there is no difference between flowers on the same plant.
However, there are several monoecious flowering plants in which the male and female organs are separated on different flowers, as a means of preventing self-fertilization. There are a lso several monoecious Gymnosperms, or non-flowering higher plants. Common flowering plants, like begonias, several trees, l ike hazels, and some grains, like corn, all have separate male and female flowers. In each case, the male flower contains sepals, petals, and stamen, while the female flowers contain sepals, petals, and pistils. Usually, it takes more than a quick look to tell whether a flower is male or female, but generally the filament-anther structure of the stamen is fairly distinct from the s tigma-ovary structure of the pistil.
Several of the non-flowering plants are dioecious, meaning the male and female organs are found on separate individuals of the same species, just like in animals. The most common exa mples of this are the ginkgoes, or maidenhair trees, and the cypresses. The male individuals can be identified by their release of pollen in the spring, while the females can be identified by their ability to produce seeds. Since gymnosperms don't have true flowers, it can be difficult to distinguish male and female cones without already knowing something about the species.
Spending some time in a garden, at a park, or even at a nursery this spring is a good way to do some field botany of your own, but don't forget that many of the flowers that you find may not look s howy, and may even not look like flowers at all.
David Hershey adds the following:
Dioecious species are not that rare among the angiosperms. About 4%, or roughly 9,400, of the known angiosperm species are dioecious with separate male and female individuals. Familiar examples include pussy willow (Salix discolor), holly (Ilex spp.), kiwi (Actinidia chinensis), pistachio (Pistachia vera), hops (Humulus lupulus), bittersweet (Celastrus scandens), date palm (Phoenix dactylifera), asparagus (Asparagus officinalis), and fig (Ficus carica).
Grant, S. et al. 1994. Genetics of sex determination in flowering plants. Developmental Genetics. 15:214-230.
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