Recipe for fast recovery after flooding

Flooding of agricultural areas may result in the loss of crops. Until recently, scientists who study the influence of flooding on plants have mostly focused on the period of the flood itself. But now, biologists at Utrecht University have discovered that plants also experience stress after the water has receded. At first, they seem to be entirely in order, but a day later the leaves can suddenly appear to be dehydrated. The researchers in Utrecht have deciphered the system the plant uses to deal with stress after a flood. Their conclusions were published in the scientific journal PNAS.
 

Dehydration due to flooding

Researcher Rashmi Sasidharan at Utrecht University led the project, which discovered that the processes that take place in a plant during a flood are as important to its recovery as those that occur during the period after the flood has receded. “Like so many other plant biologists, we studied the influence of flooding on plant growth at first. But after an experiment, we discovered that certain individuals of the species Arabidopsis thaliana, which had looked healthy at the moment that we let the water drain away, suddenly appeared to be dehydrated the next day, even though the soil was still very wet.”
 

Stomata stay closed

Various factors appear to affect the speed of the plant’s recovery during the period following a severe flood. Research leader Sasidharan: “Due to the wilted leaves, we initially thought the problem might lie with the stomata. And we were right. The beautiful leaves don’t have a chance when the plant opens its stomata immediately after the flood to exchange carbon dioxide and oxygen for photosynthesis, because the plant also loses water via the stomata. Since the roots are damaged by the flooding, they aren’t yet able to compensate for that loss, so the stomata need to stay shut a bit longer. That means the plant needs to wait a bit to start photosynthesis. We discovered that the stomata open and close due to the interaction between the two hormones ethylene and abscisic acid.”
 

Oxidative stress

Another factor that the plant has to deal with, is oxidative stress. Sasidharan: “Once the water is gone, the plant is suddenly exposed to a lot of oxygen. The plant’s cells use that oxygen to produce harmful substances known as ROS, or reactive oxygen species. But the toxic substances are also important signal molecules. When a plant is exposed to them, it produces large quantities of anti-oxidants that contribute to its recovery. That makes the ROS signal essential.”

Deactivate gene for breaking down chlorophyll

Sasidharan and her former PhD Candidate and primary author of the article, Elaine Yeung, also discovered that the breakdown of chlorophyll resulting from the activation of the gene ORE1 does not help the plant’s recovery. “In the period following a flood, it is better for the plant to keep its full-grown leaves. Plants that do not activate ORE1 maintain greener leaves and recover faster”, according to Sasidharan.

Publication

A stress recovery signaling network for enhanced flooding tolerance in Arabidopsis thaliana

Elaine Yeung*, Hans van Veen*, Divya Vashisht*, Ana Luiza Sobral Paiva, Maureen Hummel, Tom Rankenberg*, Bianka Steffens, Anja Steffen-Heins, Margret Sauter, Michel de Vries, Robert C. Schuurink, Jérémie Bazin, Julia Bailey-Serres*, Laurentius A. C. J. Voesenek*, and Rashmi Sasidharan*

PNAS, 11 June 2018

* Affiliated with Utrecht University