Cotyledon

The cotyledons or cotyledon (plural cotyledons ), also cotyledon is the leaf of the plant embryo. Nacktsamige plants usually have two to many cotyledons. The angiosperms have traditionally been in the monocots and the dicots with a divided with two cotyledons, a systematic subdivision, which has substantially held until today ( with the exception of the basal orders ).

Development of cotyledons

Embryogenesis in Arabidopsis thaliana has three characteristic morphological stages. First, a radially symmetrical spherical cell is generated by a precise pattern initially synchronously dividing cells, which is referred to as globular stage embryo. Next, the cotyledon plants ( Kotyledonenprimordien ) caused by rapid cell divisions in two areas on either side of the future apex of the stem axis. It forms the heart bilaterally stage. Finally, by the axis elongation growth and development of the cotyledons developed the torpedo stage of embryo. In many species, the cotyledons grow considerably after the torpedo stage and increase cell number and size until it accounts for nearly 90 % of the total embryo mass.

Most are cotyledons greatly reduced leaves; known exceptions are the slightly feathered cotyledons of garden cress or the well-developed cotyledons in Ricinus.

Special Functions

Cotyledons, the first leaves of a germinating plant. You sit at a particular intercept, the hypocotyl. In epigäischer ( supernatural ) germination as the radishes you can come from the seed coat on the surface of the earth, become green there and then contribute to nutrient production at. Hypogeal ( underground ) germination, however, as the scarlet runner bean, they remain in the seed coat, where they act as haustorial organs either absorb the nutrients from the surrounding endosperm, or even already storage organs such as the legume family. Beans and peas are primarily consumed for their protein-rich cotyledons.

From the plumule already applied between the cotyledons, the green leaves, of which the first are called primary leaves unfold.

Designation

The name derives from the ancient kotyle / cotyle / cotylicus ( κοτύλη ), which derived a bowl-shaped drinking vessel (see Skyphos ) and, of which, a measure of capacity designated, which was measured with such a ( calibrated ) vessel ( about 270 cubic centimeters). The name was adapted in the early modern period as a medical term for the Plazentallappen the uterus. Carl Linnaeus led in 1735 as a supposedly analogous to the formation of embryos of ruminants (endometrium) as cotyledon in the botany, a ..

Nathaniel Highmore recognized the cotyledons in 1651 than leaves; Nehemiah Grew calls 1682 the lobes of the seed ( cotyledons ), the same year she called John Ray folia seminalia ( seed leaves).