Ovule , or ovule ( lat. Ovulum ), is the formation of seed plants from which (usually after fertilization ) the seed develops. Represents female sporangia ( megasporangium ) of seed plants. In angiosperms, the ovule is located in the ovary cavity; in gymnosperms , on the surface of the seed scales in the female cones .
Four megaspores are formed in the central part of the ovule ( nucellus ) as a result of meiosis of the spore of the mother cell, then three of them die, and female gametophyte is formed from one megaspore. In flowering, it is called the embryo sac , in gymnosperms it is sometimes called the primary endosperm , since in the mature seed nutrients are stored in it. Outside, the ovule is attached by the placenta to the placenta .
If the axis of the nucleus of the ovule is a continuation of the ovule, such an ovum is called atropic , or direct . If the placenta is bent, the ovule is called anatropic , or reverse . In the case when the ovule itself is bent, it is called campyllotropic , or semi- reversed [1] .
Notes
- ↑ ESBE: Campyllotropic ovule, 1905 .
Literature
- Ovule // Safflower - Soan. - M .: Soviet Encyclopedia, 1976. - ( Great Soviet Encyclopedia : [in 30 vols.] / Ch. Ed. A. M. Prokhorov ; 1969-1978, vol. 23).
- Korzhinsky S.I. Semyapochka // Brockhaus and Efron Encyclopedic Dictionary : in 86 volumes (82 volumes and 4 additional). - SPb. , 1890-1907.
- Campyllotropic ovule // Brockhaus and Efron Encyclopedic Dictionary : in 86 volumes (82 volumes and 4 additional). - SPb. , 1905. - T. add. Ia.
- Ovule in the Biological Encyclopedia Retrieved November 20, 2008
- Shamrov I.I. Morphological nature of ovule and evolutionary tendencies of its development in flowering plants // Botanical Journal. - 2006. - T. 91 , No. 11 . - S. 1601-1636 .