Just because people deserve microscopy! Here is illustrated a male meiosis, which produces the four pollen grains, in Allium senescens (Alliaceae, Asparagales). There is nothing like seeing chromosomes or cells dividing… (before I come back into writing stuff).
From left to right and top to bottom, you can see successively:
The first meiotic division with
-a prophase, the step where chromosomes are condensating from nucleic DNA;
-then a metaphase where these chromosomes unite and get paired on a metaphasic plate (it’s almost metaphysics here!);
-then an anaphase where two chromosomic sets migrate each to a single pole of the cell.
The second nuclear division follows (without telophase: DNA doesn’t turn back into the nucleus stage but immediately goes into the next steps), with
- prophase 2 (you can verify the two groups : one is above, and one slightly blurred is below);
-the end of metaphase 2 and the very beginning of anaphase 2, almost four sets of chromosomes are distinguished;
-and finally a tetrad of four microspores, which will mature into pollen grains. To date, they are still united within the callosic mother cell wall. Nuclei are easily observed in those cells…
In the pictures illustrated here, cells were stained with Acetocarmine (colors are reversed so as to increase the contrast). Scales indicate 20 micrometers.