Time-Resolved Chemical Phenotyping of Whole Plant Roots with Printed Electrochemical Sensors and Machine Learning

Abstract

Plants are non-equilibrium systems consisting of time-dependent biological processes. Phenotyping of chemical responses, however, is typically performed using plant tissues, which behave differently to whole plants, in one-off measurements. Single point measurements cannot capture the information rich time-resolved changes in chemical signals in plants associated with nutrient uptake, immunity or growth. In this work, we report a high-throughput, modular, real-time chemical phenotyping platform for continuous monitoring of chemical signals in the often-neglected root environment of whole plants: TETRIS (Time-resolvedElectrochemicalTechnology for plantRootIn-situchemicalSensing). TETRIS consists of screen-printed electrochemical sensors for monitoring concentrations of salt, pH and H2O2 in the root environment of whole plants. TETRIS can detect time-sensitive chemical signals and be operated in parallel through multiplexing to elucidate the overall chemical behavior of living plants. Using TETRIS, we determined the rates of uptake of a range of ions (including nutrients and heavy metals) inBrassica oleracea acephala. We also modulated ion uptake using the ion channel blocker LaCl3, which we could monitor using TETRIS. We developed a machine learning model to predict the rates of uptake of salts, both harmful and beneficial, demonstrating that TETRIS can be used for rapid mapping of ion uptake for new plant varieties. TETRIS has the potential to overcome the urgent "bottleneck" in high-throughput screening in producing high yielding plant varieties with improved resistance against stress.

Plant-on-a-chip: continuous, soilless electrochemical monitoring of salt uptake and tolerance among different genotypes of tomato

“…We have previously observed a similar effect in kale seedlings for multiple salts with a range of ions (including sodium salts, heavy metal salts and nutrients), and TETRIS is not limited to just measuring changes in [NaCl]. 28 To compare this observed uptake between experiments, the rate of uptake, k uptake , was calculated by taking the gradient of the slope in the log( Z ) vs. t plot (Fig. 1D).…”

“…1A). 28 The chamber comprised a transparent acrylic lid and silicone base with water reservoir, allowing the plant to photosynthesize whilst maintaining a constant humidity. Screen-printed electrodes on polyester transparency sheet were affixed to a raised platform, placed into the measurement chamber and connected to a potentiostat (PalmSens 4 by PalmSens BV, Netherlands).…”

Plant-on-a-chip: continuous, soilless electrochemical monitoring of salt uptake and tolerance among different genotypes of tomato

“…We have previously observed a similar effect in kale seedlings for multiple salts with a range of ions (including sodium salts, heavy metal salts and nutrients), and TETRIS is not limited to just measuring changes in [NaCl]. 23 To compare this observed uptake between experiments, the rate of uptake, kuptake, was calculated by taking the gradient of the slope in the log(Z) vs. t plot (Figure 1D). (D) The rate of uptake of NaCl by tomato seedlings ("Heinz 1350", 20 plants, 7 days growth) could be found by plotting log(Z) against time and fitting a line from the point of lowest impedance after addition of treatment and the point at which the impedance returns to the initial average value (if at all), with 5% tolerance.…”

“…General experimental setup of TETRIS TETRIS consisted of a measurement chamber and a disposable sensing module (Figure 1A). 23 The chamber comprised a transparent acrylic lid and silicone base with water reservoir, allowing the plant to photosynthesize whilst maintaining a constant humidity. Screen-printed electrodes on polyester transparency sheet were affixed to a raised platform, placed into the measurement chamber and connected to a potentiostat (PalmSens 4 by PalmSens BV, Netherlands).…”

“…We have previously shown that TETRIS can be adapted for use in agar, commonly used in plant experiments for Arabidopsis thaliana. 23,35 An impedance sensor can be embedded into the agar growth medium and monitor as ions are taken up by plants.…”