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Horticulture Principles and Practices

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Anther<br />

Filament<br />

Stamen<br />

FIGURE 3–41 Whole <strong>and</strong><br />

cross-sectional view of male<br />

flower parts.<br />

Microspore<br />

mother cells<br />

Cross section of anther<br />

Stigma<br />

Style<br />

FIGURE 3–42 Whole <strong>and</strong><br />

cross-sectional view of female<br />

flower parts.<br />

Ovule<br />

Ovary<br />

Ovule<br />

Carpel<br />

Pericarp<br />

(a) Simple pistil<br />

(b) Compound pistil<br />

anther, the sack that contains the pollen grains (Figure 3–41). The female reproductive<br />

parts are collectively called gynoecium. The carpel consists of three structures: the style,<br />

which is similar to the filament; is tubular <strong>and</strong> capped by the stigma, a receptacle for<br />

receiving pollen grains; <strong>and</strong> the third structure is the ovary, which contains ovules<br />

(Figure 3–42). Gymnosperms have no flowers. Instead, their reproductive structures are<br />

called strobili (singular: strobilus).<br />

If a flower has both male <strong>and</strong> female parts it is said to be perfect. When all of the<br />

four parts of a flower are present, a complete flower exists. If one or more parts are missing,<br />

the flower is said to be incomplete. Certain flowers are either male or female <strong>and</strong>,<br />

therefore, imperfect. In plants described as monoecious, both male <strong>and</strong> female flowers occur<br />

in one plant but are physically located on different parts. In sweet corn, the male flowers<br />

(tassel) occur at the terminal parts while the female flowers (silk) occur on the middle<br />

region on the leaf axil. Cucumber, walnut, <strong>and</strong> pecan are also monoecious, <strong>and</strong> as such<br />

both sexes are required for fruiting to occur in cultivation. In dioecious plants, such as<br />

date palm, holly, <strong>and</strong> asparagus, however, one plant is exclusively either male or female.<br />

Flowers may occur individually (solitary) or in a bunch or cluster (inflorescence, as<br />

in urn plant, lupine, <strong>and</strong> snapdragon). The main stalk of an inflorescence is called a<br />

peduncle; the smaller stalks are called pedicels. There are three basic types of inflorescence:<br />

head (e.g., daisy <strong>and</strong> sunflower), spike (e.g., gladiolus <strong>and</strong> wheat), <strong>and</strong> umbel<br />

(e.g., onion <strong>and</strong> carrot). These <strong>and</strong> other types of flower clusters are shown in Figure 3–43.<br />

The physical structure <strong>and</strong> display of certain flowers make them capable of selfpollination<br />

(pollen grains from the anther are deposited on the stigma of the same flower).<br />

Since the mating system excludes foreign pollen, the species tends to be genetically pure,<br />

3.8 Flowers 89

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