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Phellogen is defined as the meristematic cell layer responsible for the development of the periderm. Cells that grow inwards from there are termed phelloderm, and cells that develop outwards are termed phellem or cork (note similarity with vascular cambium). The periderm thus consists of three different layers: [1] [2]
The monocots or monocotyledons have, as the name implies, a single (mono-) cotyledon, or embryonic leaf, in their seeds.Historically, this feature was used to contrast the monocots with the dicotyledons or dicots which typically have two cotyledons; however, modern research has shown that the dicots are not a natural group, and the term can only be used to indicate all angiosperms that are not ...
Aside from cotyledon number, other broad differences have been noted between monocots and dicots, although these have proven to be differences primarily between monocots and eudicots. Many early-diverging dicot groups have monocot characteristics such as scattered vascular bundles, trimerous flowers, and non-tricolpate pollen. [5]
As stems and roots mature lenticel development continues in the new periderm (for example, periderm that forms at the bottom of cracks in the bark). [citation needed] Lenticels are found as raised circular, oval, or elongated areas on stems and roots. In woody plants, lenticels commonly appear as rough, cork-like structures on young branches.
The epidermal cells are the most numerous, largest, and least specialized. These are typically more elongated in the leaves of monocots than in those of dicots. Diagram of moderate scale leaf anatomy. Trichomes or hairs grow out from the epidermis in many species.
Often a secondary covering called the periderm forms on small woody stems and many non-woody plants, which is composed of cork (phellem), the cork cambium (phellogen), and the phelloderm. The periderm forms from the phellogen which serves as a lateral meristem. The periderm replaces the epidermis, and acts as a protective covering like the ...
Vascular cambia are found in all seed plants except for five angiosperm lineages which have independently lost it; Nymphaeales, Ceratophyllum, Nelumbo, Podostemaceae, and monocots. [1] In dicot and gymnosperm trees, the vascular cambium is the obvious line separating the bark and wood; they also have a cork cambium.
Reproducing through seeds is the most widespread method of reproduction in both monocots and dicots. However, internal seed structure is vastly different between these groups. The cotyledon is the embryonic leaf within a seed; monocots have one whereas dicots have two. The evolution of having one or two cotyledons may have arisen 200-150 Mya ...