A Mobile NMR Sensor and Relaxometric Method to Non-destructively Monitor Water and Dry Matter Content in Plants

Abstract

Water content (WC) and dry matter content (DMC) are some of the most basic parameters to describe plant growth and yield, but are exceptionally difficult to measure non-invasively. Nuclear Magnetic Resonance (NMR) relaxometry may fill this methodological gap. It allows non-invasive detection of protons in liquids and solids, and on the basis of these measures, can be used to quantify liquid and dry matter contents of seeds and plants. Unfortunately, most existing NMR relaxometers are large, unwieldy and not suitable to measure intact plants or to be used under field conditions. In addition, currently the appropriate NMR relaxometric methods are poorly suited for non-expert use. We here present a novel approach to overcome these drawbacks. We demonstrate that a basic NMR relaxometer with the capability to accept intact plants, in combination with straightforward NMR and data processing methods, can be used as an NMR plant sensor to continuously, quantitatively and non-invasively monitor changes in WC and DMC. This can be done in vivo, in situ, and with high temporal resolution. The method is validated by showing that measured liquid and solid proton densities accurately reflect WC and DMC of reference samples. The NMR plant sensor is demonstrated in an experimental context by monitoring WC of rice leaves under osmotic stress, and by measuring the dynamics of water and dry matter accumulation during seed filling in a developing wheat ear. It is further demonstrated how the method can be used to estimate leaf water potential on the basis of changes in leaf water content.

In situpod growth rate reveals contrasting diurnal sensitivity to water deficit inPhaseolus vulgaris

“…Similarly, more straightforward, sensor-like applications of mobile NMR have been demonstrated by using small scale NMR devices (NMR sensors; NMRS) as online sensors to measure changes in water content in growing trees and pods ( Rascher et al , 2011 ; Lechthaler et al , 2016 ). More recently, an NMRS coupled with relaxometric analysis was shown to enable the concurrent, real-time quantification of both solid and liquid matter in situ ( Windt et al , 2021 ). Using a custom designed C-shaped NMR magnet, NMR coil, and magnet housing, plant samples can be inserted into the NMRS to monitor the development of plant tissues through developmental stages with little to no impact on the tissue under investigation (see also: Windt and Blümler, 2015 ).…”

“…This capacity gives unprecedented insight into the dynamics of tissue growth with potential to add significantly to our fundamental understanding of seed yield development in cropping systems. The NMRS enables the observation of diel variation in organ growth with high precision ( Rascher et al , 2011 ; Windt et al , 2021 ) facilitating the observation of growth rates across diurnal time scales and developmental processes. Using this approach, it has been shown that dry matter accumulation in reproductive tissues of wheat continues under dark conditions ( Windt et al , 2021 ), suggesting that processes such as starch remobilization and phloem transport supply photoassimilates for tissue maintenance and growth.…”

“…The NMRS enables the observation of diel variation in organ growth with high precision ( Rascher et al , 2011 ; Windt et al , 2021 ) facilitating the observation of growth rates across diurnal time scales and developmental processes. Using this approach, it has been shown that dry matter accumulation in reproductive tissues of wheat continues under dark conditions ( Windt et al , 2021 ), suggesting that processes such as starch remobilization and phloem transport supply photoassimilates for tissue maintenance and growth. The dynamics of these processes in response to water deficit likely influence the determinacy and susceptibility of yield development to changes in resource supply.…”

The exposome paradigm to predict environmental health in terms of systemic homeostasis and resource balance based on NMR data science

“…67,68 This is a useful approach to evaluate the crystalline state 69 and determine carbon chain lengths of fatty acid mixtures. 70 As a result, NMR-based relaxometry is widely used in various industries and research elds such as plants, 71 point-of-care testing, 72 food 73,74 and materials. 75,76 For the characterization of constituents in complex materials using low-resolution NMR relaxometry data, Laplace inversion using sparse representation methods has been applied.…”

Intraspecific differences in plant functional traits are related to urban atmospheric particulate matter

“…2d, the leaf dry matter content of T3 was significantly higher than that of T1 and T2 (p < 0.01), but there was no a significant difference between T1 and T2. Leaf dry matter content can reflect the adaptability of leaves to arid climates, and is the most stable variable on the axis of resource acquisition [49]. Leaf dry matter content is the preferred index in plant ecology research, and it can be a good indicator of the plant's ability to preserve nutrients [43,50].…”