Spatial and temporal detection of root exudates with a paper-based microfluidic device

Abstract

Root exudates control critical processes in the rhizosphere, retaining water, selecting for beneficial microorganisms or solubilising nutrients prior to uptake by the plant. Analysing root exudation patterns however is challenging because existing methods are often destructive and unable to resolve spatial and temporal variations in the production of root exudates. Here, we present a paper-based microfluidic device with integrated colorimetric sensors for the continuous extraction of root exudates along plant roots. The microfluidic device used standard filter paper wax printer to create channels for water to carry the exudates towards the sensors. TiO 2 nanotubes/alginate hydrogel-based sensors were used to analyse the glucose content of the root exudates of living plants. The study shows that the paper microfluidic substrate successfully extracts the released glucose from the root, and transfers it to the hydrogel-based sensor to be calorimetrically detected from independent sections of the root at different times, up to 7 days. The method was tested on two different wheat varieties Triticum aestivum (rgt Tocayo and Filon varieties), where significant differences in exudation patterns were recorded. The researchdemonstrates the feasibility of low cost technological solution for high precision screening and diagnostic of the biochemical composition of root exudates.

Plant phenotyping relevance

植物根からの滲出物を空間・時間分解して連続測定する紙ベースマイクロ流体デバイスを開発・検証しており、根の生理的形質（滲出パターン）の取得が中心である。

Code and data availability

The paper reports root exudate glucose measurements via a paper-based microfluidic device, but no public phenotype dataset, image collection, analysis code, or trained model is deposited. The authors state only that data are in the manuscript/Supplementary Information, with no repository or URL. ImageJ is a generic, un

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