Abstract
BackgroundInvestigating plant mechanisms to tolerate freezing temperatures is critical to developing crops with superior cold hardiness. However, the lack of imaging methods that allow the visualization of freezing events in complex plant tissues remains a key limitation. Magnetic resonance imaging (MRI) has been successfully used to study many different plant models, including the study of in vivo changes during freezing. However, despite its benefits and past successes, the use of MRI in plant sciences remains low, likely due to limited access, high costs, and associated engineering challenges, such as keeping samples frozen for cold hardiness studies. To address this latter need, a novel device for keeping plant specimens at freezing temperatures during MRI is described.ResultsThe device consists of commercial and custom parts. All custom parts were 3D printed and made available as open source to increase accessibility to research groups who wish to reproduce or iterate on this work. Calibration tests documented that, upon temperature equilibration for a given experimental temperature, conditions between the circulating coolant bath and inside the device seated within the bore of the magnet varied by less than 0.1 °C. The device was tested on plant material by imaging buds from Vaccinium macrocarpon in a small animal MRI system, at four temperatures, 20 °C, − 7 °C, − 14 °C, and − 21 °C. Results were compared to those obtained by independent controlled freezing test (CFT) evaluations. Non-damaging freezing events in inner bud structures were detected from the imaging data collected using this device, phenomena that are undetectable using CFT.ConclusionsThe use of this novel cooling and freezing device in conjunction with MRI facilitated the detection of freezing events in intact plant tissues through the observation of the presence and absence of water in liquid state. The device represents an important addition to plant imaging tools currently available to researchers. Furthermore, its open-source and customizable design ensures that it will be accessible to a wide range of researchers and applications.
Highlights
Woody plants’ adaptations to withstand freezing temperatures are key for their survival in environments with extreme winter temperatures, as well as, in the case of agricultural crops, for the attainment of consistent yields under the threat of climate change [1,2,3,4]
Woody plant buds are vulnerable to damage by extreme freezing temperatures [5]
Engineering challenges are of particular concern when attempting the study of plant buds with Magnetic resonance imaging (MRI) at freezing temperatures, given the need to keep plant samples at consistent freezing temperatures within the MRI equipment for many hours. Addressing these challenges, the objective of this report is to describe the design, fabrication, and testing of a low-cost MRI-compatible sample holder and cooling device that enables the controlled freezing of plant specimens while samples are scanned in an MRI device
Summary
Woody plants’ adaptations to withstand freezing temperatures are key for their survival in environments with extreme winter temperatures, as well as, in the case of agricultural crops, for the attainment of consistent yields under the threat of climate change [1,2,3,4]. Insight into the freezing mechanisms used by plant tissues can be determined by the acquisition of images at a series of different temperatures [7], allowing researchers to infer where and when ice is being formed This approach results in a robust technique for the study of plant cold hardiness [11]. Despite its benefits and past successes, the use of MRI in plant sciences remains low, likely due to limited access, high costs, and associated engineering challenges, such as keeping samples frozen for cold hardiness studies. To address this latter need, a novel device for keeping plant specimens at freezing temperatures during MRI is described
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