Question

Apomictic embryo in citrus arises from
(a) Maternal saprophytic tissue in the ovule
(b) Antipodal cells
(c) Diploid cells
(d) Synergids

Answer 1

It's the method during which the replacement of the traditional amphimixis by agamogenesis, without fertilization. Its offspring are genetically just like the parent plant. It occurs in a minimum of 33 families of flowering plants and has evolved multiple times from sexual relatives.

Complete answer:
Apomixis may be a quite agamogenesis during which a viable embryo is made within the confines of the testa, without meiosis and syngamy. Adventive embryonic may be a sort of Apomixis found in Citrus during which there's the formation of additional embryos thanks to sporophytic budding. At least one diploid sporophytic cell, either nucleus or integuments, goes through phases of embryogeny and in the end, become full-grown incipient organisms.

Additional information: Non Recurrent apomixis: during this type "the megaspore cell undergoes the standard meiotic divisions and a haploid embryo sac [megagametophyte] is made. The new embryo may then arise either from the egg (haploid parthenogenesis) or from another cell of the gametophyte (haploid apogamy)." The haploid plants have half as many chromosomes because of the mother plant, and "the process isn't repeated from one generation to another'' (which is why it's called nonrecurrent). cf. parthenogenesis and apogamy below.
Adventive embryony: they arise from cells of the nucellus of the integument. Adventive embryony is vital in several species of Citrus, in Garcinia, Euphorbia dulcis, mango, etc.
So the correct answer is ‘(a) Maternal saprophytic tissue within the ovule’.

Note: Apomictic species or individual plants often have a hybrid origin and are usually polyploid. In plants with both apomictic and meiotic embryology, the extent of the different kinds can contrast at various seasons, and photoperiod additionally can change the extent. It appears unlikely that there are any truly completely apomictic plants, as low rates of amphimixis are found in several species that were previously thought to be entirely apomictic.