Dicotyledon
historical grouping of flowering plants From Wikipedia, the free encyclopedia
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The dicotyledons, also known as dicots, are one of the two groups of flowering plants (angiosperms). The name refers to their seeds having two embryonic leaves or cotyledons. There are around 200,000 species in this group.[1]
| Dicotyledon | |
|---|---|
.JPG) | |
| Lamium album (white dead nettle) | |
| Scientific classification | |
| Kingdom: | |
| (unranked): | |
| Synonyms | |
|
Dicotyledoneae | |
The other group of flowering plants were called monocotyledons or monocots, with one cotyledon. Historically, these two groups formed the two divisions of the flowering plants.
Sequence analysis showed what botanists already suspected: dicotyledons are not a monophyletic group. They are a number of lines, such as the magnoliids, and groups now known as basal angiosperms. They diverged earlier than the monocots did. The traditional dicots are a paraphyletic group.
The largest clade of the dicotyledons are known as the eudicots. They are definitely monophyletic. They differ from all other flowering plants in the structure of their pollen. Other dicotyledons and monocotyledons have an older type of pollen, whereas eudicots have derived pollen.
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Apart from cotyledon number, there are other differences between monocots and dicots. These are differences mainly between monocots and eudicots. Many early-diverging dicot groups have "monocot" characteristics such as scattered vascular bundles, trimerous flowers, and old-type pollen.[2] Also, some monocots have dicot characteristics such as reticulated leaf veins.[2]
| Feature | In monocots | In dicots |
|---|---|---|
| Number of parts of each flower | In threes (flowers are trimerous) |
In fours or fives |
| Number of furrows or pores in pollen | One | Three |
| Number of cotyledons (leaves in the seed) |
One | Two |
| Arrangement of vascular bundles in the stem |
Scattered | In concentric circles |
| Roots | Develop from various places |
Develop from the bottom of seedling |
| Arrangement of major leaf veins | Parallel | Reticulate |
| Secondary growth thickens stem |
Absent | Often present |
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