Nucellus
In botany, the nucellus is the tissue in the ovule of the seed plants that forms the megaspores (megasporangium). It is enclosed by one or two sterile covers, the integuments , and together with them forms the ovule.
In the generation change of plants, a distinction is made between the sporophytes and the gametophytes . The sporophyte forms a tissue that forms the asexual spores , called the sporangium. From these spores, the gametophytes develop, which form the sex cells ( gametes ), which then fuse to form a zygote ( fertilization ), from which a new sporophyte emerges. This is still the case with Moosen , for example.
In the seed plants , the female gametophyte is reduced to a few (sometimes one) cell (s), completely in the so-called " megaspore ", which is referred to as endosporia . The spores that the male gametophytes reside in are much smaller and are called microspores. This hidden generation change was only discovered by Wilhelm Hofmeister in 1851 , which is why "Nucellus" is only the counterpart of the seed plants for the megasporangium of the lower plants.
The nucellus of the flowering plants is often broken down after fertilization, but can also take on the function of storing nutrients as a perisperm .
Web links
- Nucellus in the Lexicon of Biology
Individual evidence
- ^ Nucellus. In: zeno.org. Retrieved May 20, 2017 .
- ^ P. Sitte, EW Weiler, JW Kadereit, A. Bresinsky, C. Körner: Strasburger Textbook of Botany, 35th Edition, page 799, ISBN 3-8274-1388-5