Thanks Michael, appreciated.
Well, I've been mounting some of Wednesday's sections and haven't found the heart-shaped embryo stage - but, I have been lucky enough to have several slides showing the very, very earliest stage of the embryo. The fertilised egg-cell becomes a zygote, which then begins it's transformation to a fully-formed embryonic plant within a seed - awaiting germination.
The very first cell divisions of the zygote form the 'suspensor' - the 'stalk' essentially atop of which the embryo develops. We've seen the 'globular' stage and the very start of the 'heart-shaped' stage, but I now have a few images of the stage immediately after formation of the suspensor and before formation of the 'sphere of cells' that is the globular stage.
This stage of very first cell-divisions of the embryo proper consists of only 2 or 4 cells!
Here's a picture of this extremely early stage - this is before the previously seen globular and early heart-shaped stages... This is stained with Safranin-O and Alcian-blue counterstain - I love the bright Alcian-blue - but if not applied and removed very quickly (say 5 seconds max) if will render the Safranin dull.
Here's a nice image of the cells of the ovule - the nuclei can be seen suspended by the cytoplasmic skeleton - rendered this stringy-form by the fixative, in particular the acetic-acid component. This is often called the 'acid fix figure' I believe. I like it for the detail and the stain colours which are pretty bright yet clear.
This tissue is stained with the marvellously metachromatic 'Toluidine Blue' - a sort of (aqueous) 'all in one' that stains in different colours - usually pinks, reds, purples, light blue and darker blue shades - also an excellent stain for live tissue. For permanently-mounted tissue it has to be handled carefully - if it encounters a slightly alkaline solution (such as with tap water) rather than de-ionised water during the rinsing and dehydration stages it simply 'blues' and become monochromatic. Here it has performed very nicely and maintained its differentiation right through to mounting.
Here's a nice Safranin and Fast-green staining of the ovary's funiculus that connects it to the parent plant and runs into the side of the integument that folds over the ovule.
Here's a whole achene and ovary stained with Methylene-blue - another metachromatic stain related to Toluidine-blue - it too is very sensitive to pH and easily loses it's metachromasia if rinsed with a trace of alkali. If again added strong and fast the effect is far better than a long and weaker exposure (staining time).
and,
I thought I may as well post these extra images as I have used a few different stains that some may not have seen very often. The trick is to stain to maximise contrast and brightness whilst avoiding the loss of detail that often occurs. Sometimes it's good, sometimes not - but I've improved my staining lately and am pretty please with 'where I'm at' - it's a very long learning curve - but such fun and so rewarding.
Still plenty more sections to be cut from that set of tissue-blocks - I'll have some more made soon - hopefully with some interesting morphology to show you - at the very least I'll have a practice with some more stains I think!
Back soon.
