Factors influencing real time internal structural visualization and dynamic process monitoring in plants using synchrotron-based phase contrast X-ray imaging.

Chithra Karunakaran,Rachid Lahlali,David M L Cooper,Ning Zhu,Kyle Fransishyn,Jeremy Olson,Emil Hallin,George Belev,Marina Schmidt,Adam M Webb,Tomasz Wysokinski

doi:10.1038/srep12119

Chithra Karunakaran, Rachid Lahlali + Show 9 more

Open Access

https://doi.org/10.1038/srep12119

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Abstract

Minimally invasive investigation of plant parts (root, stem, leaves, and flower) has good potential to elucidate the dynamics of plant growth, morphology, physiology, and root-rhizosphere interactions. Laboratory based absorption X-ray imaging and computed tomography (CT) systems are extensively used for in situ feasibility studies of plants grown in natural and artificial soil. These techniques have challenges such as low contrast between soil pore space and roots, long X-ray imaging time, and low spatial resolution. In this study, the use of synchrotron (SR) based phase contrast X-ray imaging (PCI) has been demonstrated as a minimally invasive technique for imaging plants. Above ground plant parts and roots of 10 day old canola and wheat seedlings grown in sandy clay loam soil were successfully scanned and reconstructed. Results confirmed that SR-PCI can deliver good quality images to study dynamic and real time processes such as cavitation and water-refilling in plants. The advantages of SR-PCI, effect of X-ray energy, and effective pixel size to study plant samples have been demonstrated. The use of contrast agents to monitor physiological processes in plants was also investigated and discussed.

Highlights

Study of surface characteristics of plants or plant structures[1] at high spatial resolution (~2 nm), and as three dimensional (3D) objects
The experimental setup used for acquiring projection (2D) images using absorption and phase contrast imaging (PCI) modalities at the biomedical imaging and therapy beamline-bending magnet (BMIT-BM beamline) is shown in Supplementary Figure (F1)
The venation system and internal structures of the cotyledon and stem of a 10 day-old canola plant were most clearly revealed by PCI

Summary

Introduction

Study of surface characteristics of plants or plant structures[1] at high spatial resolution (~2 nm), and as three dimensional (3D) objects. CLSM has been effectively used to visualize cellular structures as well as to produce 3D images of larger anatomical structures of plant tissues with high resolution[3,4,5], including visualization of endophytic microorganisms in plant roots[6] using fluorescent dyes[7] These microscopic techniques require a variety of time consuming sample preparation methods and staining agents to improve differentiation of specific sample features[8]. DEI requires complex set up and the data acquisition time is about three times higher than PCI18 For these reasons, SR-PCI was selected as the best candidate technique to study low density light element plant tissues, especially for events like cavitation. The objectives of this work using an SR X-ray source were to: 1) compare absorption imaging and PCI of live plant parts; 2) determine the optimum X-ray energy for SR-PCI of seedlings in vivo; 3) determine the optimum effective pixel size required for plant imaging using PCI; 4) determine the best soil type to image plant roots in vivo; and 5) explore the use of contrast agents to monitor physiological and dynamic processes in live plants

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Conclusion