Question

Nucellar embryos found in Citrus sp. are
(a)Parthenogenesis
(b)Aposporous
(c)Apogamous
(d)Adventives

Answer 1

Hint: Nucellar embryony is a type of embryonic development that occurs without fertilization and the embryo doesn't develop from the gametes. It is a type of seed reproduction in which nucellar tissue can produce polyembryony.

Complete answer:
Nucellar embryos seen in Citrus sp are adventives.
It is a form of seed production mainly seen in citrus varieties in which the nucellar tissue surrounding the megagametophyte can carry out polyembryony i.e. produce additional embryos. These seedlings are identical to the parent plants. Unlike these, Zygotic seedlings inherit both parents' genetic material as they are produced by the result of sexual reproduction. Though both of them are different, zygotic and nucellar embryos can occur in the same seed.
This nucellar embryony culture is very important in commercial production of the uniform rootstock of citrus that yields consistent results in production. However, in the plants that possess this Nu+ trait, interference in cross-breeding is also noticed. For example, Scion varieties produce nucellar seedlings that do not inherit any paternal traits.

So, the correct answer is “Adventives”.

Notes:
Parthenogenesis is the process of asexual reproduction in which the growth of the embryo takes place without any fertilization by sperm. It is a component process of apomixis i.e. replacement of the normal sexual reproduction by asexual reproduction. In some cases like bryophytes, the sporophytes have the ability to produce a plant that looks like a gametophyte. But these plants have the ploidy level of a sporophyte. This phenomenon is known as apospory. On the other hand, the gametophytes of certain bryophytes have the ability to develop a group of cells that has similar look to sporophytes but has the ploidy level of the gametophytes. It is known as apogamy.