A typical angiosperm has bilobed anther and its microsporangium has four microspore mother cells. How many tetrads and pollen grains will be formed in it?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 16 tetrads and 64 pollen grains
A typical angiosperm anther is bilobed, and each lobe has two theca (it is dithecous). So one anther has four microsporangia. In each microsporangium, every microspore mother cell (a cell of the sporogenous tissue) undergoes meiosis and forms one microspore tetrad, a group of four cells. Each microspore then develops into a pollen grain.
Microsporangia in one anther = 2 lobes × 2 = 4
Microspore mother cells = 4 microsporangia × 4 = 16
Tetrads = 16 (one from each mother cell)
Pollen grains = 16 × 4 = 64
(1) 4 tetrads and 4 pollen grains — Incorrect. This counts only one microsporangium, and it also forgets that each tetrad has four cells.
(2) 16 tetrads and 64 pollen grains — Correct. 16 mother cells give 16 tetrads, and each tetrad gives 4 pollen grains.
(3) 64 tetrads and 16 pollen grains — Incorrect. The two numbers are reversed. There are always four times as many pollen grains as tetrads, never fewer.
(4) 64 tetrads and 64 pollen grains — Incorrect. The number of tetrads cannot equal the number of pollen grains, because each tetrad gives four pollen grains.
NCERT Extract:
Stamen, Microsporangium and Pollen Grain – “… A typical angiosperm anther is bilobed with each lobe having two theca, i.e., they are dithecous (Figure 1.2b). Often a longitudinal groove runs lengthwise separating the theca. Let us understand the various types of tissues and their organisation in the transverse section of an anther (Figure 1.3a). The bilobed nature of an anther is very distinct in the transverse section of the anther. The anther is a four-sided (tetragonal) structure consisting of four microsporangia located at the corners, two in each lobe.”
Stamen, Microsporangium and Pollen Grain – “… As the anther develops, the cells of the sporogenous tissue undergo meiotic divisions to form microspore tetrads.”
Figure 1.2 (a) A typical stamen; (b) three–dimensional cut section of an anther
