Let's say you've carelessly dunked your hand into a vat of liquid nitrogen and let it freeze solid. Every movie you've seen where this happens tells you that your hand will shatter like fine china should you bump it into something. If you're extremely careful, will your hand be okay once it thaws out? We'll explore this issue, using flower and onion cells rather than our hands!
Announcer: Frostbite Theater presents... Cold Cuts! No baloney!
Joanna and Steve: Just science!
Joanna: Hi! I'm Joanna!
Steve: And I'm Steve!
Joanna: By now, we all know what happens when you place a flower in liquid nitrogen.
The water within it freezes and makes it much easier to crush.
Joanna: But, what if we don't crush it? Will the flower return to normal once it warms up?
Once it thaws, it only takes about 20 minutes for it to wilt away.
Steve: So, what's going on?
We borrowed a microscope from our friends over in the Surface Characterization Lab, which is run by the College of William and Mary, to find out! Unfortunately, other than a color change, it isn't easy to see what happened to the flower's cells.
So, we tried a piece of onion! There's clearly some activity going on inside the cells before they get frozen and the cell walls look like cell walls should.
The story's different once they're frozen and thawed, though. The cell walls are fractured and, if we zoom in, all the activity we saw earlier has stopped.
Joanna: The problem, of course, is that water expands when it freezes. So, if a cell is full of water when it freezes, that's going to be a problem. If your goal is to cryogenically preserve something, you need to figure out a way to replace the water with something else.
Thanks for watching!
I hope you'll join us again soon for another experiment!
Steve: You just love crushing my flowers, don't you?
Joanna: This one's yours too, isn't it?
Joanna: Ha! I'm going to crush all of them!
A special thanks to Michelle, Olga and Nick for the use of their microscopes. The College of William and Mary's Surface Characterization Lab rocks!
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