Question

The sequence of development of embryo sac is
A. $Archesporium{\text{ }} \to Megaspore{\text{ }}mother{\text{ }}cell{\text{ }} \to Megaspore{\text{ }} \to Embryo{\text{ }}sac.$
B. $Archesporium{\text{ }} \to Megaspore \to Megaspore{\text{ }}mother{\text{ }}cell{\text{ }} \to Embryo{\text{ }}sac.$
C. $Archesporium{\text{ }} \to Megaspore \to Megaspore \to Embryo{\text{ }}sac.$
D. None of these

Answer 1

Embryo sac is the structure within a plant ovule that contains the egg cell. It develops from megaspore and contains the embryo plant and endosperm after fertilization.
A single hypodermal cell of the nucleus in the ovule or megasporangium, called the archesporium cell behaves as a megaspore mother cell.

Complete answer:
The classification of development of embryo sac is based on:
(1). The number of 9 spore nuclei entering into the formation of embryo sac. Thus, embryo sac may be monosporic, bishopric or tetrasporic type.
(2) It can be monosporic, simple or polygonum type.
(3). The total number of nuclear divisions occurring during megasporogenesis and development of female gametophyte.

A single megaspore mother cell matures within the ovule. Through meiosis, a single mother cell forms four haploid megaspores and this process is called megasporogenesis. Out of the four megaspores, only one remains functional and the rest three degenerate. This functional megaspore then develops into embryo sac or female gametophyte by the process of mega gametogenesis The nucleus of functional megaspore divides three times by mitosis to form 8 nuclei which then get organized to form 7 celled and 8 nucleate embryo sac.

This option is correct as the sequence of development of embryo sac is

B. This is not the correct sequence of development of embryo sac. Hence, this option is not correct.
$Archesporium{\text{ }} \to Megaspore{\text{ }}mother{\text{ }}cell{\text{ }} \to Megaspore{\text{ }} \to Embryo{\text{ }}sac.$

C. Option C does not include a megaspore mother cell. Hence, this option is not correct.
D. This option is not correct because according to the question the correct sequence of development of embryos is given in Option A.

So, our correct answer is option A.

Note: The embryo sac is surrounded by a cellulosic wall sometimes complete with cellulose as in maize. The commonest pattern of embryo sac is the polygonum type (monosporic, eight nucleate). In total, the embryo sac is composed of seven cells each of which has a precise role during the fertilization process.