CSU graduate student examines drought tolerance of plants

Robert Griffin-Nolan
Robert Griffin-Nolan

With every degree increase in Celsius, the atmosphere can hold 7 percent more water. Given rising global temperatures, this means longer periods without rain and more intense storms when precipitation does happen.

Robert Griffin-Nolan, a graduate student in the Ecology Program at Colorado State University, studies drought tolerance in grasslands. He recently published a paper on validating the use of a new physiology method on herbaceous plants.

“If we want to understand which ecosystems and which plant communities are going to be more sensitive or resilient to climate change and extreme droughts, we need to understand at the community level how species respond to drought,” Griffin-Nolan said. “If we have a community that has high prevalence of species with drought tolerance, then it might not be so sensitive to drought.”

Plants differ in their ability to maintain leaf hydration during drought, as anyone who forgets to water their house plants knows. The trait that describes this wilting point of a plant is called “leaf turgor loss point.” Griffin-Nolan tested a recently developed method for estimating this trait.

While scientists have been able to measure the turgor loss point of a leaf for some time, the process was previously time-intensive. It could take up to 48 hours.

A 50-fold faster way to measure the leaf turgor loss point on trees was recently developed by researchers out of the University of California, Los Angeles. Griffin-Nolan took this method and tested it on a variety of herbaceous plants including grasses in Colorado, Wyoming and Kansas. Some researchers were skeptical that the method would work for grasses because of their densely-veined, thin leaves.

“A lot of physiology methods are developed for trees because they are both easier to study than grasses and are a bit more charismatic,” Griffin-Nolan said, “But understanding drought tolerance in grasses is really important because they cover a huge proportion of Earth’s land surface, often growing in water-limited systems.”

Grasslands cover more than 30 percent of the earth’s surface and are composed of species that deal with drought regularly. Many of these species have evolved ways of dealing with drought, while many are highly sensitive to changes in precipitation and drought.

Working together

To clarify that this new method of estimating leaf turgor loss point works for herbaceous plants, Griffin-Nolan collaborated with researchers from USDA Agricultural Research Service, scientists from Cleveland State University and professors from CSU’s Departments of Biology and Forest and Rangeland Stewardship.

Griffin-Nolan hopes that the speed of this new technique will allow researchers to examine the leaf turgor loss point in multiple species in a given community or across a broader scale. Understanding drought tolerance in communities and ecosystems could improve predictions about responses to rising global temperatures across the planet.

This method is being used to look at community level drought tolerance in an ongoing research project called Extreme Drought in Grassland Ecosystems. Griffin-Nolan is participating in this project with a team of other researchers at CSU, the University of New Mexico and the University of Oklahoma.

After graduating this spring, Griffin-Nolan will fly to Japan in June to start a new research project addressing the physiology of invasive species in their home versus away ranges. He will be working as a postdoctoral scholar through Syracuse University conducting research in collaboration with Professor Jason Fridley. Griffin-Nolan will continue to study the relationship between plant physiology and larger global processes.