Morphological Parts of Monocot Seed
Angiosperms, the flowering plants, are classified into two classes by the morphology of their seeds. Monocots have a single, or "mono," cotyledon in their seeds and dicots have two, or "di," cotyledons in their seeds. Cotyledons are seed leaves, which are structures found within the seed that function for nutrient storage in dicots and perform secretory and absorptive functions in monocots. The structure of these two types of seeds is different.
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A Typical Seed
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All true seeds share three basic structures: an embryo, storage tissue and a seed coat. The embryo will become the new plant. The storage tissue is called endosperm, and provides nutrients for the growing embryo. The seed coat provides protection for the seed.
Monocot Endosperm and Coat
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All angiosperms undergo double fertilization. The haploid egg (n) fuses with the haploid sperm (n) forming the embryo (2n). Another sperm fuses with two female nuclei to form endosperm (3n). The nutrient endosperm of most monocots surrounds the cotyledon, taking up the majority of the space inside the seed. This endosperm is shuttled to the cotyledon as needed during growth. The endosperm is surrounded by the seed coat, or testa.
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Monocot Cotyledon
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The cotyledon is surrounded by endosperm. The cotyledon, in turn, surrounds the embryo. Endosperm shuttles through the cotyledon to provide nutrients for the embryo. There is only one cotyledon in monocots.
Monocot Hypocotyl and Epicotyl
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The hypocotyl is located below the cotyledon. The lower part of the hypocotyl is called the radicle. The radicle becomes the roots. The epicotyl is located above the cotyledon. This will become the stem and leaves. When a monocot first germinates, only one leaf emerges, called a plumule. When a dicot first germinates, it produces two small leaves.
Embryo
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The embryo of cereal and grain monocots is quite developed, consisting of the coleoptile, the scutellum, the radicle and the coleorrhiza. The coleoptile becomes the shoot sheath, which protects the plumule and shoot meristem as it pushes through the soil. The scutellum acts as the cotyledon, absorbing nutrients from the endosperm. The coleorrhiza is the first structure to grow through the seed coat.
Representative Monocots
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Wheat, barley, rice, maize, oats, rye, millet, onions, garlic, ginger, banana, palms, grasses, orchids, lilies and bamboos are a few representatives of monocot plants.
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