Project

Using ultrasound for drought stress quantification

A new technology based on ultrasound has the potential to quantify in real-time the water status in plants. The company Plense has developed a first prototype of a sensor that is attached to the stems of plants to detect the ultrasonic signal generated by the water movement in the xylem. This project search to validate this technology by comparing this signal with different measurements that normally serve as proxies for the quantification of water status in plants.

Project description

Monitoring crop water status in real-time not only can assist irrigation management, but also it can provide insights on the physiological mechanisms underlaying crop responses to drought stress. This knowledge is essential for adapting agronomic practices as well as for selecting new cultivars that are more resilient to water deficit. Most of the approaches available for monitoring crop water status rely either on labor intensive leaf-level methodologies, or on indirect estimations using crop models or remote sensing. In either case, the translation of these estimations to real-time crop water status is difficult. The company Plense Technologies has been working in developing an innovative technique that uses ultrasound to monitor plant water status in real-time. Their new sensor is able to “hear” the flux of water in the xylem! Water moves through the xylem as a result of the potential gradient generated by the transpiration in the leaves. If this gradient becomes large due to high transpiration, tiny air bubbles form in the xylem. When the bubble is formed, a measurable ultrasonic pulse is created that provides information about the geometry of the xylem, water content and sap flow. Following this principle, the sensor produces short ultrasonic pulses that bring the vascular bundles of the plant into resonance. The resulting vibration response is received by the sensor and, based on machine learning, translated into quantitative measurement data related to the plant’s water balance. The Plense sensor has been tested in a small pilot experiment on tomato plants, showing that the sensor gets different vibration responses with varying plant water balance. This project is intended as the next step, where we will try to calibrate the sensor and validate the signal as a direct and quantitative measurement of plant water status. In collaboration with Plense and the Netherlands Plant Eco-phenotyping Centre (NPEC), we will conduct an 8-weeks experiment using potato and maize plants subjected to contrasting water. The plants will be cultivated under controlled conditions at the Plant-Ditech system (NPEC) for detailed monitoring of their transpiration and growth over time, enabling a thorough characterization of the plants response to drought. Simultaneously, the ultrasound sensor will be attached to the stems of the plants.

Objectives and methods

Objective: Validate and quantify an ultrasound technology (Plense’s sensor) as an approach for monitoring drought stress in plants.

Experiment: We will conduct an 8-weeks experiment using potato and maize plants. These two crop species differ in their photosynthetic pathway (potato is a C3 plant and maize is a C4 plant) which translates into differences in water use efficiency. Each of the species will be subjected to contrasting water regimes. The combination species x treatment will ensure variability in plant water potential, resulting in different levels of drought stress. The plants will be grown under controlled conditions at the Plant-Ditech system (NPEC) for thorough characterization of their transpiration and growth. The ultrasound sensor will be attached to the stems of the plants. The installation and monitoring of theses sensors will be supervised by Plense in coordination with the student.

Activities:

  1. Co-supervise the greenhouse experiment together with the NPEC personnel.
  2. Conduct complementary measurements at leaf level including stomatal conductance, chlorophyll content (SPAD meter) and other photosynthetic traits. The water use efficiency at plant level will estimated by measuring the final plant biomass.

Analyze all the collected data in order to validate and elucidate the physiological meaning of the signal detected by the ultrasound sensors.

Expectations

We expect that we can describe the physiological meaning of the ultrasound signal detected by the Plense’s sensor by using the data collected at leaf level and also using the NPEC technology.

Required skills

  • Data analysis and interpretation
  • Proficiency in using sensors and equipment for
    measuring physiological parameters (e.g. porometer, IRGA, SPADmeter)

Types of research/work

Research work, which includes conducting a greenhouse experiment and data analysis.

Period

Mid of September 2024 until middle of March 2025. The experiment will start on October 7th 2024.

Location

WUR - NPEC

Supervisor