How does the megaspore mother cell develop into 7-celled, 8 nucleate embryo sac in an angiosperm? Draw a labeled diagram of a mature embryo sac.

Solution

The nucleus of the functional megaspore mother cell divides mitotically to form two nuclei which move to the opposite poles, forming the 2-nucleate embryo sac. Subsequent mitotic nuclear divisions result in the formation of the 4-nucleate and later the 8-nucleate stages.

of the embryo sac. These mitotic divisions are strictly free nuclear in nature, that is, nuclear divisions are not followed immediately by cell wall formation. Among the eight nuclei, six are enclosed by cell walls and organised into cells, while the remaining two nuclei (called polar nuclei) are situated above the egg apparatus in a large central cell. Out of the six cells, three are grouped at the micropylar end, and constitute the egg apparatus out of which two are synergids and one egg cell. The other three cells are located at the chalazal end, and are called antipodals. All this leads to the organisation of the typical female gametophyte or embryo sac which is 8-nucleated and 7-celled.

Some More Questions From Human Reproduction Chapter

For Daily Free Study Material Join wiredfaculty

Human Reproduction

How does the megaspore mother cell develop into 7-celled, 8 nucleate embryo sac in an angiosperm? Draw a labeled diagram of a mature embryo sac.

Some More Questions From Human Reproduction Chapter

Seminiferous tubules open into vasa efferentia through :

Polar bodies are produced during the process :

In 28 days woman's menstrual cycle, ovulation occurs on :

Scrotum communicates with abdominal cavity through :

How many spermatozoa or sperms are present in human ejaculate ?

Acrosome is a part of:

Humans are :

Menstrual cycle occurs in :

Spermatozoa are produced in the .................. tubules of testes while ova are formed in the .................. of ovaries.

Corpus luteum secretes..................while Leydig cells secrete..................

Mock Test Series

NCERT Sample Papers

Entrance Exams Preparation

Phone Number

Email Address

Location