The laboratory now has a cryo-stage for the scanning electron microscope! But let's take a step back in case this type of microscopy is new to you. Basically a scanning electron microscope (SEM) shoots electrons at a sample that is placed in a chamber under high vacuum. The electrons bounce off the sample and enable you to detect an image of the surface that is at a much higher magnification than you can see with a light microscope. The light (dissecting) microscope that I have in the lab magnifies 50-250X, whereas the SEM can magnify up to 200,000X! That is pretty awesome in and of itself, but the cryo-stage adds a whole other level to this equipment. Typically the samples that you look at have to be completely dry before placing them into the vacuum. This is a big issue for biological samples, which can be full of water. There are a number of ways to get rid of the water, but these processes often change the shape of the structures. For some studies this is not a major issue, but for other studies scientists are really trying to see what the plants or animals look like when they are hydrated as they would be when alive.
Cryo-stage to the rescue! With this equipment a sample can be flash frozen in liquid nitrogen with all of the water in place and then placed into the microscope on the chilled cryo-stage. Then the sample can be viewed with the tissues fully hydrated.
I was out of town when they used some of my moss samples for a test run, so I didn't get to see the equipment in action, but here are some of the images that were taken.
This is a leafy gametophyte stem with a cluster of antheridia at the apex. We are looking down at the top of the stem and there is a second leafy gametophyte lying on its side in the background. The leaves are fully expanded and in an arrangement that you would see when hydrated. If they were dry they would be all folded and curled up on themselves.
Here is the cluster of antheridia and hairs at higher magnification.
And at an even higher magnification. The hairs located in the antheridia clusters in the Funariaceae are characterized by having a large apical cell, which we can see here is fully hydrated. The filaments covering the hairs are probably fungs or bacteria. These mosses were grown in the laboratory but not in sterile conditions.
Some of the leaves were removed from the gametophyte to make for easier viewing. This image shows the inside of the leaf cells. The outline of the cell walls are visible and it is super cool that we can see the water filling each of the cells.
Congratulations to Dr. Cantino and colleagues on their successful National Science Foundation research grant that funded this new piece of equipment.