The embryo , also the embryo [1] (in botany ), is the germ of a new sporophyte , an asexual (diploid) generation in the development cycle of higher plants .
The embryo is characteristic of both higher spore and seed plants .
The embryo develops from the zygote , a cell formed by the fusion of two gametes during the sexual process.
The embryo is largely composed of educational tissue .
Embryo Structure
In seed plants, the embryo is part of the seed and consists of the following parts:
- The germinal root is the part from which the main root of the plant develops.
- Hypocotyl , or hypocotyl , or embryonic stalk , or submucosal knee - the part located in the embryo between the germinal root and plume ; later - the part of the plant that is located between the main root and the main shoot ; in anatomical terms, the hypocotyl also occupies an intermediate position between the root and the stem . When the seed sprouts above the soil surface, it is usually the hypocotyl that first becomes visible - at first it has the shape of a loop, and then, straightening, draws the cotyledons and the embryonic kidney from the soil.
- The embryonic kidney , or plume , is the part from which the main shoot of the plant develops.
- Cotyledons , or seed breeders , or germinal leaves are the first leaves of a plant that develop at the embryo in the seed; often differ significantly from subsequent leaves - both in shape and in internal structure, and sometimes in function. In gymnosperms, the number of cotyledons is from two to eighteen, and their number can vary even within the species . Monocotyledonous cotyledons have one, dicotyledons usually have two (but there are exceptions: for example, some types of magnolia can have either two or three cotyledons, and degeneration can have either three or four cotyledons, but never two, which is considered as primitive trait inherited from gymnosperm ancestors [2] ). In some highly specialized monocotyledonous plants, the cotyledon was transformed into a special organ that protects the embryonic kidney - the coleoptile , which has the appearance of a cap (scutellum); during seed germination, it breaks through the soil with a hard top [3] .
There are many representatives of flowering plants in which the embryo is not differentiated. In some cases, such an organization of the embryo is a sign of primitiveness, in others it is a sign of reduction (secondary simplification). In orchids , as well as in many parasitic (for example, from the Zarazikhovy families) and saprophytic (for example, from the Grushanka family of Heather ) subfamilies, the embryo is precisely reduced, but it is often difficult to establish whether it is primary or secondary. [3]
Sprout of Aleppo pine ( Pinus halepensis ) with eight cotyledons
Sprouts of Hypericum perforatum ( Hypericum perforatum ) with two cotyledons
The sprout of a species of palm trees in Washington , Washingtonia filifera with one cotyledon
Notes
- ↑ Korovkin, 2007 .
- ↑ Takhtadzhyan A. L. The family of degenerative (Degeneriaceae) // Plant Life. In 6 t. / Ed. A. L. Takhtadzhyana. - M .: Education , 1980. - T. 5. Part 1. Flowering plants. - 430 s. - 300,000 copies. - S. 121-125.
- ↑ 1 2 Khrzhanovsky VG Course in General Botany (cytology, histology, organography, reproduction): Textbook for agricultural universities. Part 1. 2nd ed. - M .: Higher school , 1982.- 384 p. - 55,000 copies. - S. 314-315.
Literature
- Germ // Euclid - Ibsen. - M .: Soviet Encyclopedia, 1972. - ( Great Soviet Encyclopedia : [in 30 vol.] / Ch. Ed. A. M. Prokhorov ; 1969-1978, vol. 9).
- Korovkin O. A. Anatomy and morphology of higher plants: glossary. - M .: Bustard, 2007 .-- 268 p. - (Biological Sciences: Dictionaries of Terms). - 3000 copies. - ISBN 978-5-358-01214-1 .
- Subcotyledonous knee // Fee - Prob. - M .: Soviet Encyclopedia, 1975. - ( Great Soviet Encyclopedia : [in 30 vols.] / Ch. Ed. A. M. Prokhorov ; 1969-1978, vol. 20).
- Cotyledons // Safflower - Soan. - M .: Soviet Encyclopedia, 1976. - ( Great Soviet Encyclopedia : [in 30 vols.] / Ch. Ed. A. M. Prokhorov ; 1969-1978, vol. 23).