Question

In a type of apomixis known as adventive embryony, embryos develop directly from the______
a. Nucellus or integuments
b. Synergids or antipodals in an embryo sac
c. Accessory embryo sacs in ovule
d. Zygote

Answer 1

Hint: Organisms reproduce to sustain their generation. Plants also undergo reproduction in order to increase the population of species. But sometimes reproduction is not done by regular means. Apomixis is a process in which plants undergo asexual reproduction without undergoing fertilization. It asexual formation of seed. Adventive embryony is one such example.

Complete answer:
Apomixis have various types in flowering plants such as-
• Recurrent apomixis- It is a type of gametophytic apomixis. It generally arises from some other parts of the nucellus.

• Non-recurrent apomixis- The mother cell undergoes meiotic divisions like usual. The new embryo may arise from the egg through parthenogenesis.

• Vegetative apomixis- The flowers are replaced with bulbils in this type.

• Adventive embryony- It refers to the formation of an embryo somewhere else than within an embryo sac. In this type, the adventive embryo may develop from nucleus or integument and do not arise from the gametophyte. It may occur together with a normal zygotic embryo. The most common example includes that of the Citrus plant. It is also referred to as sporophytic apomixis.

Hence, the correct answer is option (A).

Note: Some important points-
• The term apomixis was first defined by Hans Winkler.
• In flowering plants, the term is generally used to denote agamospermy( reproduction through seeds).
• Apospory- The sporophytes of non-flowering plants may also have the ability to form a plant that looks like a gametophyte but with the ploidy level of the sporophyte(n). It is also known as somatic apostrophe.