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.
Highlights
Grasslands sequester high amounts of carbon in their soils [1,2,3], enabling them to potentially mitigate the concentration of greenhouse gases in the atmosphere [4]
Roots are at the core of plant water dynamics and water status by enabling water uptake from the soil
A 14 h light cycle was applied with lamps on from 8:00 a.m.2 to−110:00 p.m., and an an intensity of photosynthetic active radiation (PAR) of 560 μmol2 m−1s, and off during 10 intensity of photosynthetic active radiation (PAR) of 560 μmol m s, and off during 10 h
Summary
Grasslands sequester high amounts of carbon in their soils [1,2,3], enabling them to potentially mitigate the concentration of greenhouse gases in the atmosphere [4]. The first step of this process is carbon fixation by photosynthesis in plant leaves, which is tightly coupled, at the leaf level, with transpiration, i.e., the outgoing flux of water in a plant. Carbon sequestration processes depend on plant’s water fluxes in the soil–plant–. Under optimal edaphic water conditions, water flows from areas of higher water potential (soil) to areas of lower water potential (air) [5]. This differential of water potential pulls water from the soil into plant roots, up through the vascular system, and out of stomata in the leaves, thereby impacting the entire water status of the plant. Plant water fluxes vary according to external parameters like radiation, soil water availability or plant characteristics such as total leaf area, root density, root conductance, root phenology, as well as circadian rhythm [5]
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