Question

Space occurs between nucellus and integument towards the micropylar end. It is called.
A. Endostome
B. Endothecium
C. Endothelium
D. Endosperm

Answer 1

Hint: The ovule is the structure of the female reproductive that gives rise to the female reproductive cells. Network of features that forms the covering of an organism is generally known as integument.

Complete answer:
The ovule is composed of the integument, forming its outer layer, the nucellus (or remnant of the megasporangium), and the female gametophyte (formed from a haploid megaspore) in its center. A mature ovule consists of a food tissue covered by one or two future seed coats, known as integuments. A small opening (the micropyle) in the integuments permits the pollen tube to enter and discharge its sperm nuclei into the embryo sac.

Option a: The space between nucellus and inner integument towards the micropylar end, is called endostome. Within the ovule, an opening is formed at the tip of the ovule due to the absence of integuments is called the micropyle. It acts as a pore for the entry of the pollen tube into the ovule for fertilization. Therefore, this is the correct option.

Option b: Endothecium is the lining of the cavity of anther. It secretes materials that are essential for the proper maturation of the pollen grains. Therefore, this is an incorrect option.

Option c: Endothelium is a thin membrane that lines the inside of the heart and blood vessels. It forms an interface between circulating blood or lymph in the lumen and the rest of the vessel wall. It lines the interior surface of blood vessels and lymphatic vessels. Therefore, this is an incorrect option.

Option d: Endosperm is the tissue that surrounds and nourishes the embryo in the seeds of angiosperms. It is triploid in most species. Therefore, this is an incorrect option.

Thus, the correct option is (a) Endostome.

Note:It is to be noted that the opening formed by the outer integument is termed as exostome and when it is formed by both the integuments and termed as amphistome.