Question

What is called filiform apparatus?

Answer 1

Hint: Filiform apparatus is a finger-like projection, which consists of a core of microfibrils sheath to assist the pollen tube while entering the ovule. They also resemble the transfer cells and extracts food from the nucleus. It is made up of pecto cellulosic fibres that are evolved in the non-cellulosic sheath.

Complete answer:
The embryo sac or female gametophyte is formed by functional megaspore. The nucleus of the functional megaspore divides into two, four, and finally eight daughter nuclei. Two nuclei come to the centre to form two polar nuclei and then further fuse to secondary nuclei.

Antipodal cells are formed by the three nuclei present at the chalazal end of embryo sac. The remaining three nuclei form pyriform cells at the micropylar end and get surrounded by cytoplasm. And these three cells constitute the egg apparatus, consisting of an egg and a pair of synergids or help cells.

A special cellular thickening present in the synergids at the micropylar end is called filiform apparatus. After fertilization when the egg cell gives rise to zygote, they get disorganized. The major function is to guide the entry of pollen tubes into synergids and to release sperm cells. The invaginations of cell walls into protoplasm made the filiform apparatus to form.

Note: The function of synergid is the secret chemotactic substance for the attraction of pollen tubes. During the pollen entry, one synergid becomes degenerate, thus giving the way for the entry of the pollen tube into the embryo sac.