Precision Control: Engineering a Multi-Partition Growth Chamber

May 25, 2017

By Echo Martin

Traditional growth chambers control several environmental factors, such as humidity, light, and temperature. Some experiments, however, require more precise control of multiple factors—such as salinity and air composition—which traditional growth chambers either don’t manage efficiently or can’t manage at all. Traditional growth chambers just didn’t cut it for the Hegeman lab, where scientists are trying to gather data on plant metabolomics over time, but researcher Calvin Peters had the solution. Peters engineered specialized multi-partition growth chambers that can control almost any aspect of a plant’s environment—allowing for more precise measurements and better-controlled experiments.

The key to the metabolomics research currently underway in the Hegeman lab is carbon. The basic experiment starts with seedlings being germinated in the dark, as light is needed for carbon fixation. Once the plants have germinated they’re placed into the chamber, sealed, and purged with CO2-free air. Researchers pump in 13CO2, which contains a stable isotope of carbon called carbon-13. Over time, the chambers are switched individually back to 12CO2. At different points in a plant’s life cycle researchers freeze the plant in liquid nitrogen and measure the change of the isotope through the plant.

“You can actually trace the carbon isotope,” says Peters. “It has no physiological effect on the plant, but just changing the carbon isotope changes the weight of the molecules incorporating it, which can then be measured.”

With previous labeling growth chambers, researchers would need to switch the carbon isotope on all the plants in the chamber at the same time. This meant that an experiment would need to be restarted from the beginning to get data points further along in the plant’s growth. Because Peters’ chambers are partitioned, they can alter the isotope on a single group of plants at different points in a plant’s growth cycle to gather more detail on how different processes change over time.

The system appears intimidating, but the parts aren’t special. “Other than the aluminum base, which we had custom built,” says Peters, “everything is made from easily accessible parts. You can get things like the electronics and the pods from anywhere that sells computer or growth chamber parts.” Peters has a dual degree in chemistry and biochemistry and was hired to research metabolic flux, but electronics has always been a hobby of his. “I drew it all up using CAD software, and programmed it using C, C++, and Python.”

Light, media pH, water content, humidity, and more are all controlled in each chamber to ensure consistency throughout the experiment. Adding nutrient solution or removing waste can be done without opening the chambers. “Its automated design minimizes human intervention and avoids hazards,” says Peters. “The computer is basically just a display; the chambers run on their own independent of the computer. Even if the laptop crashes, microcontrollers still run the chambers.”

These chambers are useful for studying metabolic flux, but they have potential far beyond this application. They can be used to easily study a combination of stresses, such as salinity, light, nutrient solution, heat/cold, or CO2. They are extremely customizable, and will ensure that the variables not being studied remain consistent.

“When it runs right, it’s incredibly satisfying,” says Peters. Other labs have shown interest in the chambers Peters has created, but as of yet he hasn’t heard of anyone building something similar. His experience with this project has led him to pursue a software engineering degree while he continues his work in the Hegeman lab. “The chambers aren’t complete,” he says. “There’s always something else to do and a way to make it better.” Though the chamber may be made up of easily accessible parts, the precision it provides to the Hegeman lab and other researchers who utilize it has value beyond measure.