Question

Which of the following forms monosporic embryo sac?
a. Oenothera type
b. Fritillaria type
c. Allium type
d. None of the above

Answer 1

When the mature embryo sac is laid into order in an egg apparatus with an uninucleated central cell it is also called Oenothera type. The micropylar megaspore of the tetrad gives hike to this embryo sac by two nuclear divisions that results in the formation of four nuclei in the form of two synergies, egg as well as a polar nucleus.

Complete answer:

Oenothera type:
In Oenothera type is like Polygonum type, is a usual linear tetrad of megaspores is formed, but instead of the innermost one, the outermost megaspore which is present towards micropyle remains functional along with performing its functions it is also forms the embryo sac. The functional megaspore undergoes two successive divisions along with it forms 4 nuclei.

Fritillaria type:
Fritillaria Type is a type of embryo sac that occurs in a large number of genera. In this case scenario, Three out of four megaspore nuclei are arranged in 3 + 1 order. Three nuclei migrate to the chalazal end. The remaining nucleus comes at the micropylar pole.

Allium type:
Allium is a genus of monocotyledonous plants that consists of hundreds of species, including the cultivated onion, garlic, scallion, shallot, leek, and chives. The generic name Allium is derived from the Latin word for garlic, as well as it is a type species for the genus is Allium sativa which means "cultivated garlic".

Hence, the correct answer is option (A).

Note: The third division is absent in Oenothera type along with it all the nuclei are situated in the micropylar region of the developing embryo sac. Resulting in a lower polar nucleus as well as antipodal cells is absent.