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How do cotyledons differ between eudicots and monocots?
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plant development
The life cycle of the fern. (1) Clusters (sori) of sporangia (spore cases) grow on the undersurface of mature fern leaves. (2) Released from its spore case, the haploid spore is carried to the ground, where it germinates into a tiny, usually heart-shaped, gametophyte (gamete-producing structure), anchored to the ground by rhizoids (rootlike projections). (3) Under moist conditions, mature sperm are released from the antheridia and swim to the egg-producing archegonia that have formed on the gametophyte's lower surface. (4) When fertilization occurs, a zygote forms and develops into an embryo within the archegonium. (5) The embryo eventually grows larger than the gametophyte and becomes a sporophyte.
The primary difference between eudicots and monocots regarding their cotyledons lies in their number: monocot embryos possess a single cotyledon, whereas eudicot embryos typically have two.12
These embryonic seed leaves serve critical roles in plant development by supplying nutrition to the germinating seedling, either by storing reserves themselves or by absorbing nutrients from the endosperm. Their specific functions and structures often reflect these taxonomic differences:2
- Monocots: The single cotyledon frequently acts as a specialized absorbing organ. For example, in grasses, it is modified into an enzyme-secreting structure called a scutellum, which helps mobilize and withdraw nutrients from the endosperm.2
- Eudicots: When reserves are stored directly within the two cotyledons, these organs may shrink and die after germination, or they may develop chlorophyll and become the plant's first photosynthetic organs.2
Regardless of the group, cotyledons do not usually persist long after the seedling becomes nutritionally independent.2