With flooding intensity and frequency predicted to increase by roughly 7% for every 1°C increase in global average temperatures, University of Illinois entomology professor Esther Ngumbi writes that scientists must consider the impacts of floods to "protect the monumental gains made in building climate-resilient crops."
Photo by Fred Zwicky
Ngumbi has questions — lots of them — and she's using unconventional methods to answer some of them. She is purposely flooding tomatoes to see how they might respond to flooded conditions in farmers' fields — a scenario that is becoming more common as a result of climate change.
Ngumbi says that in nature "there are many stressors on plants during flooding. Once the tomatoes get flooded, they're already weak, so most likely they will be attracting insects, which like to eat weaker plants. We're investigating how the plants deal with the combined stress of flooding and herbivory."
Half of the tomato plants in the greenhouse Ngumbi works in are flooded, the other half are not flooded, allowing her team to compare the stressed plants with those grown in more common conditions. But more investigations are going on here.
Ngumbi explains: "Within this experiment, we are also looking at microbes. We want to understand how the microbial community changes in flooded conditions."
One of Ngumbi's key focuses is how soil microbes influence plant health and productivity. She's fascinated by mycorrhizal fungi, which form intimate associations with plant roots, offering essential elements like nitrogen to the plants in exchange for glucose supplied by the roots.
Photo by Fred Zwicky
The tomato plants are all growing in soil from an Illinois farm, but half were also inoculated with mulch from a local farmer who has developed his own recipe for nurturing mycorrhizal fungi in the soil. Ngumbi wants to see if this inoculation makes any difference to the plant's ability to defend itself from caterpillars.
Two years after beginning this experiment, Ngumbi published her results. She found that the two tomato varieties differed in gene expression and in the volatile compounds they emitted — before any intervention. When flooded, both varieties of tomatoes had very different chemical emission profiles than when grown in normal conditions. Herbivory influenced the production of these volatile compounds, but not as much as flooding did.
Today, the experiments continue, and Ngumbi's interest in the effects of flooding has only intensified. In a new review published in the journal Trends in Plant Research, she spells out the many changes that occur when plants are inundated with water for days or weeks at a time. Flooding disrupts plant metabolism and energy generation. It interferes with photosynthesis. Flooding kills beneficial bacteria and promotes pathogenic microbes in the soil. It also can compromise plants' ability to defend themselves from disease and harmful insects like the tobacco hornworm.
Writes Ngumbi: "Flooding is different from other climate-related stressors because it deprives plants of oxygen, an essential and indispensable element, and substrate for plant growth and development."
Ngumbi also warns that increased flooding can undermine decades of research aimed at making plants more resilient to climate change. Flooding may thwart efforts to build soil quality and microbial health to make crops more resilient to stressors such as heat and drought. Flooding also may eliminate gains derived from genetic engineering or plant breeding.
For more information:
University of Illinois
https://illinois.edu