Category Archives: D2O Effects on Life

Recreating Crumley: The setup (Updated)

Hi!

I’m setting up the Crumley Experiment now that I have most of what I need. I ordered some more tobacco seeds but I have no idea when those are set to arrive so I’ll begin a preliminary experiment with what I have to work out the kinks. If you are too lazy to click the link above then I’ll recall for you that the experiment involved putting tobacco seeds in different percentages of D2O and tracking seed germination.

Their setup was to put seeds in petri dishes on moist cloth. I found these slide/petri dish hybrids called Analyslide that seemed perfectly suited to this and I’m going to omit the moist cloth and instead just fully submerge the seeds. The volume of the dish portion seems pretty low (less than 5mL is my guess) and the lids create a nice seal which will hopefully keep deuterium exchange to a minimum.

I built a photography system for the dishes which works a little like an inverted microscope. The slides sit up high on some cage system rods (from Thor Labs) and the camera is mounted on a rail below aimed upward. Currently I have to use a mirror to see in the eyepiece, but I’m thinking of equipping a webcam under the camera so I can see precisely what I’m looking at.

You can see the setup below with some dummy slides and some test images. I wanted to see how easy it would be to focus on something in the Analyslide so I wrote “HI!” on a piece of paper and taped it inside. It worked pretty well.

Update: I forgot to mention where the water comes from! It is very easy to overlook that fact since water is the most used chemical in the lab. When Koch talks about setting up osmotic pressure experiments he always mentions that water is the most overlooked variable because it is everywhere and we take it’s effect on the experimental world for granted. Anyways:

All water is purchased from Sigma-Aldrich, except DI water which comes from a Thermo purifier in the lab. I purchased D2O in a 100g amount bottle product number 151882. Deuterium depleted water (DDW) is also purchased in 100g amounts and has the product number 195294.

The DI water comes from a Barnstead EasyPure RoDI filtration system from Thermo Scientific, with part number D13321. I took a picture of ours for your viewing pleasure below.

Barnstead EasyPure RoDI

Repeating Crumley et al (1950)

Koch asked me in a comment to replicate an experiment done in 1950 by Helen A Crumley et al demonstrating Tobacco seed growth in deuterium oxide (D2O). The experiment is rather simple (and the figure from the paper is shown below) as Crumley placed 100 seeds in differing amounts of D2O (double distilled water, 33%, 66%, and 99.8% D2O) and analyzed the growth.

Influence of ordinary water, 33%, 66%, and 99% deuterium oxide on tobacco seed germination. Counts made at daily intervals for 39 days. (From Crumley, Fig 3)

So here I am planning the experiment. I will change some things from their experiment. First they placed the seeds on wet cloths (paper towels?), and I will submerge the seeds in the water amounts they used. They also used a variety of plant species (tobacco, clover, radish, Kentucky bluegrass), where I will just use tobacco seeds (but I will try two different species). Finally they talk about their results in terms of percent germination, but it isn’t clear from the paper if they mean number of plants that have exhibited germination, or if they are referring to some amount of growth exhibited by each plant. I will look for both possibilities and report the results as I find them.

In a preliminary experiment I will submerge the plants in water in petri dishes and seal it with parafilm. I will be looking into a more airtight solution as time goes on. I also won’t do 100 seeds but probably on the order of 33 seeds per sample. And in the future I will look into figuring out a way to measure the seed growth.

Original Crumley paper can be found here.