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Horticulture Principles and Practices

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FIGURE 3–43<br />

type.<br />

Inflorescence<br />

Spike Panicle Raceme Corymb Simple umbel<br />

(a) Solitary<br />

flower<br />

Compound umbel Catkin Cyme Head Dichasium<br />

(b) Inflorescence<br />

Epicotyl<br />

FIGURE 3–44<br />

A dicot seed.<br />

Hyocotyl<br />

Radicle<br />

Testa<br />

Hilum<br />

Groove<br />

Notch<br />

Beak<br />

Hilum<br />

Cotyledon<br />

FIGURE 3–45<br />

caryopsis.<br />

A monocot<br />

Corn caryopsis<br />

Pericarp<br />

Aleurone<br />

Coleoptile<br />

Endosperm<br />

Scutellum<br />

(Cotyledon)<br />

(a) Whole<br />

Coleorhiza<br />

Tip<br />

(b) Transverse section<br />

Radicle<br />

Black layer<br />

or homozygous. Imperfect flowers have no choice but to engage in cross-pollination<br />

(pollen transferred from one flower <strong>and</strong> deposited on a different flower). Insects, birds,<br />

mammals, <strong>and</strong> wind are all agents of this process that promotes heterozygosity by permitting<br />

foreign pollen to be deposited.<br />

3.9 SEED<br />

Monocot<br />

A type of angiosperm<br />

characterized by seeds<br />

with only one seed leaf or<br />

cotyledon.<br />

Horticultural plants may be seed bearing (gymnosperms <strong>and</strong> angiosperms) or nonseed<br />

bearing (cryptogams). Seeds remain dormant until the proper environmental conditions<br />

for germination prevail. A seed contains an embryo, or miniature plant (sporophyte), that<br />

is encased in a seed coat, or testa, in dicots <strong>and</strong> a pericarp in monocots. In dicots, the<br />

embryo is s<strong>and</strong>wiched between two structures called cotyledons, which function as storage<br />

organs (Figure 3–44). Monocots have one cotyledon, which is called a scutellum in<br />

90 Chapter 3 Plant Anatomy

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