Study: The Titanium:Sapphire laser is used to convert high-intensity green sunlight into bio-friendly wavelengths. Credit: University of Nottingham
Researchers trying to understand fluid motion in living plant tissues have found that it is difficult to observe water uptake within roots without damaging them.
Kevin Webb, Optics and Photonics Research Group's study lead, says, "To observe water absorption in living plants without damaging them," and that a sensitive laser-based optical microscopy technique has been used to non-invasively see water movement within living roots. This is something that was never done before.
Fundamentally, how plants can thrive and produce crops depends on their ability to absorb water and manage it. Water is an essential solvent for nutrients, minerals, and other biomolecules within plant tissues. We have a method that allows us to see the process at the level single cells. We can see water moving up the root and also how it moves around.
"Feeding the growing world population is already a problem. Climate change is creating huge changes in the distribution and density of waterfalls on the planet, which can lead to difficulties growing crops in areas hit by flooding or droughts. The goal of increasing global food productivity is to select plants that can better cope with stress. This involves understanding and using plant varieties that have the highest survival rates in all environments, regardless of how dry or moist.
How it works
For the study, water transport measurements were performed on the roots of Arabidopsis thaliana, which is a 'model plant' for scientists since they can be easily genetically-engineered to interfere with basic processes like water uptake.
The new imaging technique, based on the Nobel Prize-winning Raman scattered technique, allowed researchers to measure the water flowing up through Arabidopsis' root system at the cellular level and to create a mathematical model to quantify and explain this.
Researchers used heavy water (deuterium dioxide, or D2O), that contains an extra neutron in each hydrogen atom's nucleus. It was possible to observe the 'heavy water' moving through the root tip by scanning the laser with a straight line while the plant drank.
These measurements, combined with the mathematical model, revealed a significant water barrier in the root of Arabidopsis. This revealed that water uptake in the root's central tissues is limited, where the water vessels are located.
Malcolm Bennett, Professor in Plant Sciences at the University and co-lead of the project, stated that "this innovative technique is an important game-changer for plant scienceenabling researchersto visualize water movement at a cells and second level within living plant tissues. This is the first time this has been done." This will allow us to answer important questions like how plants sense water availability. These answers are crucial for designing future crops that can adapt to climate change and changing weather patterns.
These findings, which were funded by the Leverhulme Trust, were published in Nature Communications as a paper entitled "Noninvasive hydrodynamic imaging of plant roots at cellular resolution".
The initial focus of the research was on plant cells. These cells are approximately 10 times larger than human cells, making them easier to observe. These same methods are being used by the research team to study human cells in order to see exactly the same processes on a smaller scale.
The human body has tissues that handle water. This is just like plants. For example, fluid handling diseases can affect transparent tissues in the eyes, such as glaucoma, macular degeneration, and ocular lens cataracts. The new Raman imaging technology could be a useful tool for healthcare monitoring and detection.
Researchers are working to commercialize their hydrodynamic Raman imaging technology. They have applied for funding from four UK and EU agricultural companies to study tracers that travel from plant roots to plant leaves in order to understand water transport. The team is also developing portable versions of the technology that will allow farmers and scientists to measure water transport in the field. This will enable them to monitor water handling in crops grown in difficult local environments.
The current bid for the European Research Council Synergy Grant is being made by the research team with UK partners. This grant will allow the research team to study water uptake and drought resistance in order to develop a new tool that can help determine how certain crops can be adapted to specific local conditions.
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Flavius C. Pascut and colleagues, Non-invasive Hydrodynamic Imaging in Plant Roots at Cellular Resolution, Nature Communications (2021). Journal information: Nature Communications Flavius C. Pascut et. al., Non-invasive Hydrodynamic Imaging in Plant Roots at Cellular Resolution, (2021). DOI: 10.1038/s41467-021-24913-z