Sunflower embryo sacs - very early stages

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mrsonchus
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Sunflower embryo sacs - very early stages

#1 Post by mrsonchus » Mon Nov 27, 2017 12:55 am

Hi all, you may have seen my earlier thread re Sunflower (Helianthus.annus) embryos at the very early globular and pre-heart stages...

The sections of tissue were taken from the very young, small and only partly-opened flower-heads of some of the rather tragic Sunflowers that I grew (or at least attempted to grow - my Darling Wife said the kids in the local infant school had grown better Sunflowers.... she was I'm afraid quite correct, much to my shame... :oops: ) this Summer..

So, here's a recap-image of the early 'globular' stage of a very young embryo's life (the embryo is at this stage a 'ball of cells' on a stalk - the suspensor).
(I'm posting these images into the forum as Google's hosting is rather unpredictable at the moment it seems, so only 5 images per post - but several posts! :D :D )

Globular-stage embryo at 8µ - slightly thinner sections than the first ones of the earlier thread (they were at a morphological 10-12µ at which they also had a tendency to over-stain as embryonic tissue is very dense and very often mutinucleate/polyploidal) as I'm working-towards as much detail of the cellular organisation that I can get without going too thin where cellular-integrity (mainly broken cell-walls) is lost and the whole thing gets a little messy (usually at around 2-3µ I find with most plant tissue).
ws_helianthus embryo sac (10).jpg
ws_helianthus embryo sac (10).jpg (140.88 KiB) Viewed 3260 times
Closer-in cell-walls and discrete cells are more clearly defined than the original sections, and of course mitosis is now rampant and chromosomes are visibly dividing.
ws_helianthus embryo sac (12).jpg
ws_helianthus embryo sac (12).jpg (70.92 KiB) Viewed 3260 times
I also, as well as the very effective Safranin + Fast-green staining protocol seen above, stained several slides with the lovely Toluidine-blue. The TBO has a look, and of course a metachromasia, that I find really lovely to look at - and it gives great contrast and consequently images too! Another globular embryo sits snugly in it's embryo-sac and grows like fury!
ws_helianthus embryo sac (7).jpg
ws_helianthus embryo sac (7).jpg (79.43 KiB) Viewed 3260 times
This embryo - if it is an embryo - looks to be at an even earlier stage, perhaps of only several cells, not sure,
ws_helianthus embryo sac (6).jpg
ws_helianthus embryo sac (6).jpg (108.47 KiB) Viewed 3260 times
The embryo is initially (but only for a short while in the Compositae family of which Sunflower is a member) nourished by the endosperm, which is a mass of cells surrounding the embryo and undergoing much mitosis as it enlarges, seen below,
(at least I think this is endosperm, it may be nucellus but I don't think so as nucellus is very thin and soon degenerates in Helianthus),
ws_helianthus embryo sac (13).jpg
ws_helianthus embryo sac (13).jpg (59.82 KiB) Viewed 3260 times
That's my 5, more in the next post. I love peeking into these tiny secret worlds to discover 'what goes on' inside the plants that are all around us - truly fascinating! :D :D
Back in next post with a few more images.
John B

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mrsonchus
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Re: Sunflower embryo sacs - very early stages

#2 Post by mrsonchus » Mon Nov 27, 2017 1:40 am

Here are few more images that you may like to see, as soon as I can get hold of some more mature Sunflower embryos I will present some 'further-on' sections to follow these.
I tried Sunflower-seed from 'Parrot mix' but the kernels (the actual seeds proper) once removed from the stripey fruit that we think of as the seed - still refused to infiltrate properly - the resulting attempt to section - well... ahem, It wasn't pretty.... :oops: But I shall return with mature embryo ASAP! :D :D

Anyway here are a few more 'Sunflower the early days' images!
These are mostly sectioned at 6µ and have a reasonable level of detail whilst remaining intact...

I think this is nucellus, but it may be the 'integumentary tapetum' - an epithelial layer of the enclosing 'integuments' that form the ovule's outer case, that takes over from the nucellus as it quickly degenerates after producing the megaspore (one survives from four produced) that divides and becomes the embryo-sac (the megagametophyte that produces the egg-cell - the female gamete). The individual cells are reasonably easy to see, as are the green-stained surrounding integument cells that have thankfully remained intact to a reasonable degree.
ws_helianthus embryo sac (9).jpg
ws_helianthus embryo sac (9).jpg (77.5 KiB) Viewed 3255 times
Here's a nice image (the stains are nice and bright thankfully) of an entire ovule - from the centre, the blue/green 'whispy' and sparse tissue is I think endosperm - which will be used-up or degenerate and be absorbed as the embryo enlarges.
The embryo if fertilised, or egg-cell and accompanying cells, is sitting at the bottom of the egg-sac.
Next-outwards is the lining of deeply-stained cells that is the integumentary tapetum.
At the top are some red-stained 'wavy looking' cells that I think are the remains of the nucellus - again not sure.
The red-stained channel leading to the base of the embryo-sac is the micropyle through which a pollen-tube will reach the embryo-sac end egg-cell to release the two male gametes for fertilization.
Finally the red-stained line from the lower right-hand of the image is the vascular-supply to the integument that 'feeds' the ovule from the placenta at the ovules base.
Amazing to think that all this complexity exists in the tiny embryo-sac and it's ovule!
ws_helianthus embryo sac (23).jpg
ws_helianthus embryo sac (23).jpg (92.77 KiB) Viewed 3255 times
Here are two different sections, each at 6µ, through the same embryo-sac.
Interesting to see how the view changes almost imperceptibly as the sectioning moves through the tissue. Needless to say, each ovule and embryo-sac doesn't give many, in-fact about 5 or 6, 'good views' per tissue-block!
If you look closely at the deeply-red cells of the surrounding tapetum you can see the cells are dividing 'both ways' - that is laterally and vertically (left-hand side especially) - I wish I had differentiated the Safranin a little more here!
ws_helianthus embryo sac (22).jpg
ws_helianthus embryo sac (22).jpg (66.58 KiB) Viewed 3255 times
and also a little closer-in,
ws_helianthus embryo sac (15).jpg
ws_helianthus embryo sac (15).jpg (59.55 KiB) Viewed 3255 times
One last image - sorry it's a little unclear - the slides used for these images were only mounted about 2 hours earlier and are not at their optical best for at least another week - but I can never wait that long to take images! Looks like 'something's going on' with a nucleolus here, although I'm guessing really...
ws_helianthus embryo sac (19).jpg
ws_helianthus embryo sac (19).jpg (40.33 KiB) Viewed 3255 times
Better call it a night now - I hope you like the images and sorry if I've included too much waffle - I forget sometimes that not everyone want's to know all the tiniest details - it's a habit I've always had....

Back soon, hope you like them! :D :D

John B :)
John B

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McConkey
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Re: Sunflower embryo sacs - very early stages

#3 Post by McConkey » Mon Nov 27, 2017 2:45 am

I may not 100% follow all the terms or know whats going on but one thing i do love about all your write ups is the details. You always provide a very well thought out explanation of what were looking at and for me it's always appreciated! I like to know what i'm looking at even if i dont understand it. I also really appreciate the measurements you give, helps put things in perspective!

You do a really incredible job with your slides and capturing the details in your specimens.

As always your images are great, full of colour and great detail! I especially like the first image on the second post.... image (9). It's very sharp! Really great job!

I look forward to getting my hands on some more of your slides!
Karl
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vasselle
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Re: Sunflower embryo sacs - very early stages

#4 Post by vasselle » Mon Nov 27, 2017 3:55 pm

Bonjour
Très bon sujet et les photos sont très belles.
Et bravo pour votre travail et le partage.
Cordialement serb
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mrsonchus
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Re: Sunflower embryo sacs - very early stages

#5 Post by mrsonchus » Tue Nov 28, 2017 11:33 am

Thanks Karl & Seb', you're very generous. It's great to know other folk like them too!

John B. :D :D
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billbillt
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Re: Sunflower embryo sacs - very early stages

#6 Post by billbillt » Wed Nov 29, 2017 4:06 pm

Yes, John B. needs to publish a text book..

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Re: Sunflower embryo sacs - very early stages

#7 Post by JimT » Wed Nov 29, 2017 11:21 pm

(or at least attempted to grow - my Darling Wife said the kids in the local infant school had grown better Sunflowers.... she was I'm afraid quite correct, much to my shame... :oops: )
You more than make up for it with your great sections and explanations.
John B. needs to publish a text book..
Yes but make it an "Idiots Guide" book. I ubderstand them the best.

JimT

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zzffnn
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Re: Sunflower embryo sacs - very early stages

#8 Post by zzffnn » Thu Nov 30, 2017 1:22 am

Beautiful work, John B! Thank you for sharing!

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