Question

Archesporium of ovule is
a. Single celled derived from nucellar epidermis
b. Single celled derived from nucellar hypodermis
c. Multicellular derived from nucellar epidermis
d. Multicellular derived from nucellar hypodermis

Answer 1

Hint: The group of cells from which the development of spore mother cell occurs is called archesporium. It is represented by endothecium. It is referred to as a generation of the first cell in sporogenous tissue. The archesporial cells develop into the sporogenous tissue which produces from the archesporium.

Complete answer:
During the megasporogenesis process which takes place in ovule or megasporangium, the hypodermal cells function as an archesporium cell and it will be more prominent. It is of large size with dense cytoplasm and a large nucleus. The archesporial cells function directly as a megaspore mother cell in the tenuinucellate ovules whereas it periclinally divides to form an outer parietal cell and inner primary sporogenous cell in the crassinucellate ovules. This also functions as a megaspore mother cell. So, the cell used is single-celled and it functions as a nucellus in the hypodermal cell.

The single crushed non-lignified layer of empty cells is called Nucellus epidermis or hyaline epidermis. During the development of the embryo, the nucellar epidermis stays only one cell thick. Due to its anticlinal divisions, cells of the nucellar epidermis become more or less isodiametric.

The multicellular archesporium is present in some cases of embryo sac and it will develop polyembryony or apomixis form.

The multicellular archesporium of nucellar hypodermis does not occur, which is why it is a wrong answer.

Hence, the correct answer is option (B).

Note: Nucellar can be epidermis or hypodermis as well as multicellular or unicellular (single-celled). The cells of the archesporium produce from only one cell and not from more than one cell which is named the megaspore mother cell. The function of megasporangium is done by the hypodermal cells which will develop large size archesporium and also large nucleus.