Question

In the amoeboid type of tapetum.
(a) The cell remains in situ.
(b) The cells secrete chemicals for the degeneration of middle layers.
(c) The cells pass in between the middle layers.
(d) The cells from plasmodium that pass in between pollen grain mother cells.

Answer 1

Hint: The layer of the pollen grain is made up of specialized tissues and are responsible for fulfilling the requirement of the nutrients. The cells of this layer will divide and form cells that may be either bi-nucleate or multinucleate cells.

Complete answer
The tapetum is found between the anther wall and the sporogenous tissue which consists of a specialized layer of nutritive cells. The tapetal layer is required for the nourishment of the pollen grain and for their development also. It also helps in the formation of the pollen coat which is double layered in structure. The outer layer of pollen is called exine made up of hard sporopollenin and is the most resistant substance while the inner layer is called intine. In the amoeboid type of tapetum, the tapetal cells will undergo fusion and form tapetal plasmodium. Their protoplast then surrounds the pollen grains and their protoplasm will enter the locule, this whole process occurs during the prophase stage of the meiosis. Thus, in this process, the cell will break down resulting in the movement of their whole protoplast to nourish microspores of pollen grains by moving in the center or locule.

Additional information
These tapetal cells will form bi-nucleate or multinucleated by undergoing the process of endomitosis where the nucleus in the nuclear membrane divides, but cytokinesis does not occur. The cells formed are large in size having many nuclei. The tapetal cells divide their nuclei through meiosis and it is done with the help of the sporogenous cells. The mitosis will sometimes result in the formation of the multinucleated tapetum cells as the mitosis that occurred was not normal.
The innermost layer of the tapetum is called the anther wall having a cell with cytoplasm and large prominent nuclei. These cells help in the growth and development of the pollen grains.

So, the correct answer is ‘The cells from plasmodium that pass in between pollen grain mother cells’.

Note:
Tapetum cells provide nutrients, but auxin in tapetum cells is not sufficient to support the early stages of pollen development. Tapetum is classified into two categories based on their mode and position of division, they are plasmodial (amoeboid), secretory (glandular). These glandular or secretory cells surround the lobe of the anther. The auxin produced in the sporophytic microsporocytes is required for the male gametophyte development.