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.
Laurent,
I just borrowed your Allium microsporocyte meiosis micrographs to use in my introduction to botany lecture on the plant life cycle and sex.
I shall give you full credit and congratulations on the fine micrographs!
thanks,
Larry
hi
Could you please refer me to a procedure how to obtain meiotic cells from anthers? Preferrably a detailed, easy and foolproof one :-).
You only have to find out the time when developping anthers are at the meiotic stage. The procedure is to squash these into an appropriate staining medium (here it’s Carmine Red and it’s the best so far to my knowledge) and see if you got it right. Beware it’s generally early in stamen development, always when flower is at an early bud stage. I would say that in Monocots, it is usually best to look at about 2-3 weeks before flowering time, though some species behave differently…
Dear Laurent
Thank you for the most wonderful pictures showing meiosis in pollen grains. I am going to use the image in my Grade 12 Life Sciences examination and will give you full credit.
Regards
Anne Bredenkamp
St Stithians Boys’ College: Souh Africa
Oh my, this brings back my bio teaching days!
Reblogged this on DownHouseSoftware and commented:
Check out this excellent series of micrographs of an onion cell undergoing meiosis to produce pollen. Be sure to check out the descriptions of each phase in the process as you walk through the process. The Prophase2 illustration is difficult to pick out – however, this is reality. To paraphrase Roger Waters “Reality shows what is;Textbooks illustrate what mother nature intended.”
Thank you for these excellent micrographs. Our class is in the middle of discussing cell division right now – although we stand interrupted by a pair of winter storms. I’ve reblogged so that my class can see. Also thank you for the identification of the stages, they will surely find that useful.
[…] Male meiosis in onion […]
Does meiosis take place somewhere within the onion, in that case where? Or is it some part of the onion’s flower that undergoes meiosis? (By onion I mean Allium Cepa.) Would be very helpful, thank you!
Not within onion bulb, rather, in flowers. Male meiosis in developping stamens, female meiosis in developping carpels. You should know, meiosis is for sex. Plants sexual organs are in flowers.