More spectacular microscope adventures, starring a gazillion orchid seeds!
This series of photos was actually taken last Sunday, placing the time line at 4 weeks post sowing. This first one shows the Laelia tenebrosa 'Coast Ovelins' AM/AOS x self, first shown in this post. You'll see some are much further along, some are starting to swell, and some are just sitting there thinking about it. The forming protocorms (green) have now shed their seed coats. This you can still see on the top right green mass - there is the empty husk along its bottom right side. Magnification is about 38x in this photo.
This one is Encyclia mariae, OSP #2769, magnification ~29x in the top photo, 144x in the bottom two photos, which were taken with blue light and a red-green filter. Here again you see a variety of developmental stages. The higher magnification photos also gives you a better look at the cast off seed coats, to the top right of each large protocorm. (Remember that chlorophyll naturally auto-fluoresces red under blue light, that is why they appear red in these photos) Possibly the most interesting thing about these two photos, however, is that on the bottom of the center protocorm you can see the beginnings of two nearly transparent root-like structures. I do not believe they are actual roots, but a simpler, more primitive structure. As protocorms develop, they form their first leaf and several fuzzy hairs on the other side. I suspect these are most similar to root hairs in structure, probably formed by one to a few cells each with no differentiation in terms of cell function, for the express purpose of improving water absorption over short distances. A true root has many cell types, each with its own function, shape, and location. Can anyone confirm for me the nature of the little hairs in the photo?
I also have plates of Cattleya leopoldii v. alba, OSP# 1383 which were sterilized and plated at the same time. Unfortunately these show no definite germination at this time, only an obvious difference between viable and not viable seeds. Not all seeds will germinate as quickly as the ones shown above. Hopefully these will start to germinate soon, too.