Wednesday, May 28, 2014

Improvements on measuring drought tolerance

Just a quick note here on measuring drought tolerance.

In the past, we were using a pressure bomb to determine a plant's water potential at which stomatal conductance falls below a threshold (5 mmol m-2 s-1).

Using a pressure bomb on grasses can be tough. They are often just a few mm across and don't have that much water in them. Magnifying glasses just don't magnify enough.

I dug around a bit and bought a digital microscope. Turns out these work great.

First, we lock in the grass blade at a pretty high height. Note we spray painted everything black to reduce glare.

Then we place the microscope camera near the blade. The scope camera is 5 MP which gives fairly good resolution. A Macbook Pro with a Retina display is high enough resolution to show things well (most laptop monitors are only 2 MP).

The scope camera is under $100 at Amazon.

After that, we pressurize and wait for the water.

Holding things still can be problematic, but it's working pretty well to be honest. Also, what we see on the screen is a bit higher resolution than this video for some reason.

Much better than magnifying glasses.


  1. First, I've enjoyed reading this blog for the last couple years, please keep the research updates coming!

    Second, I'm wondering if you're still happy with the Celestron 5 MP scope. I read comments that the image quality it is no better than the 2 MP scope, and the image quality in your video isn't incredible.


    1. The 5 MP scope is better. You need a high resolution monitor to see it though. It can zoom in a lot closer than the 2 MP scope (at least the one we bought).

      I'll try to get a better video up. Not sure why it didn't come out better.