Circadian Variation of Root Water Status in Three Herbaceous Species Assessed by Portable NMR

Abstract

Roots are at the core of plant water dynamics. Nonetheless, root morphology and functioning are not easily assessable without destructive approaches. Nuclear Magnetic Resonance (NMR), and particularly low-field NMR (LF-NMR), is an interesting noninvasive method to study water in plants, as measurements can be performed outdoors and independent of sample size. However, as far as we know, there are no reported studies dealing with the water dynamics in plant roots using LF-NMR. Thus, the aim of this study is to assess the feasibility of using LF-NMR to characterize root water status and water dynamics non-invasively. To achieve this goal, a proof-of-concept study was designed using well-controlled environmental conditions. NMR and ecophysiological measurements were performed continuously over one week on three herbaceous species grown in rhizotrons. The NMR parameters measured were either the total signal or the transverse relaxation time T2. We observed circadian variations of the total NMR signal in roots and in soil and of the root slow relaxing T2 value. These results were consistent with ecophysiological measurements, especially with the variation of fluxes between daytime and nighttime. This study assessed the feasibility of using LF-NMR to evaluate root water status in herbaceous species.

Challenges and advances in measuring sap flow in agriculture and agroforestry: A review with focus on nuclear magnetic resonance

“…In 1998, a portable NMR device named NMR-MOUSE (Figure 4iii) was constructed by Blümich et al (1998) and used for a variety of applications, such as analysis of porosity of the materials (Blümich et al, 2010), stratigraphy of paintings in a non-destructive and non-invasive manner (di Tullio et al, 2016), leaf water status (Capitani et al, 2009), and moisture fraction in wood (Casieri et al, 2004). In a recent study, NMR-MOUSE was used to analyze the circadian variation of root water status in three herbaceous species (Nuixe et al, 2021). A further step in developing portable NMR is the use of permanent C-shape magnets (Rokitta et al, 2000).…”

Towards portable MRI in the plant sciences

“…But, as far as we know, spatially resolved root water uptake has not yet been studied with portable MRI. Nonetheless, diurnal variations of proton density and relaxation times have been observed in the roots of herbaceous species [ 46 ]. Such variations in proton density were also observed in the stems of trees [ 34 , 47 ].…”

“…[ 13 ] Sorghum bicolor (L. Moench) 0.047 2D and 3D imaging of root architecture in soils; Root segmentation Nuixe et al . [ 46 ] Dactylis glomerata ; Plantago lanceolata ; Medicago sativa 0.3 Diurnal variation in water content and in T 2 …”