Question

Draw the embryo sac of a flowering plants and label:
(a)(1) central cell
(2)chalazal end
(3) synergids
(b)name the cellthat develops into embryo sac and explain how this leads to formation of embryo sac.
(c) mention the role plays by various cells of embryo sac.
(d) give the role of filiform apparatus.

Answer 1

Answer:

a)

Explanation:

 b) The nucleus of the functional megaspore divides mitotically to form two nuclei which move to the opposite poles, forming the 2-nucleate embryo sac. Two more sequential 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, that is, nuclear divisions are not followed immediately by cell wall formation. After the 8-nucleate stage, cell walls are laid down leading to the organization of the typical female gametophyte or embryo sac.

Six of the eight nuclei are surrounded by cell walls and organized into cells; the remaining two nuclei, called polar nuclei are situated below the egg apparatus in the large central cell.

c.)Egg cell fuses with one sperm to form diploid zygote. Two polar nuclei (central cells) fuses with other sperm cell from pollen grain to form triploid cell which forms endosperm. Synergids help in the entry of sperm cells into theembryo sac.

d.)Filiform system assists in entering a pollen tube into an ovule synergy. The filiform device is a finger-like projection consisting of an enclosed core of microfibrils in a sheath. The filiform apparatusresembles the transfer cells “meaning the movement of metabolites at short distances

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