Q.
Development of a gametophyte directly from the sporophyte tissue is called
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NTA AbhyasNTA Abhyas 2020Sexual Reproduction in Flowering Plants
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Solution:
Agamospermy (Gk. agamous-without marriage, Sperma-seed) is a mode of apomixis in which seeds are formed but are asexual in nature as the embryo develops directly without gametic fusion. It is commonly formed from a diploid nucellar cell (apospory) or megaspore mother cell (diplospory). When sporophytic cells of nucellus develop to form directly female gametophyte or embryo sac, it is known as apospory.
Adventive polyembryony is the formation of additional embryos from different parts of the ovule (other than egg of the embryo sac) like synergids, antipodal cells, nucellus, integuments, etc. (e.g., citrus, opuntia, Mangifera, trillium, onion, groundnut).
Apogamy (Gk. Apo-without, gamos-marriage) is the formation of sporophyte or embryo directly from cells of the gametophyte. In higher plants, only diploid apogamy is successful, that is, the gametophytic cell forming the sporophyte is diploid. In lower plants, haploid apogamy is equally successful.
The development of the egg cell without the process of fertilization to form an embryo is called parthenogenesis.