In vivo Observation of Tree Drought Response with Low-Field NMR and Neutron Imaging

Abstract

Using a simple low-field NMR system, we monitored water content in a living tree in a greenhouse over 2 months. By continuously running the system, we observed changes in tree water content on a scale of half an hour. The data showed a diurnal change in water content consistent both with previous NMR and biological observations. Neutron imaging experiments show that our NMR signal is primarily due to water being rapidly transported through the plant, and not to other sources of hydrogen, such as water in cytoplasm, or water in cell walls. After accounting for the role of temperature in the observed NMR signal, we demonstrate a change in the diurnal signal behavior due to simulated drought conditions for the tree. These results illustrate the utility of our system to perform noninvasive measurements of tree water content outside of a temperature controlled environment.

Is desiccation tolerance and avoidance reflected in xylem and phloem anatomy of two coexisting arid‐zone coniferous trees?

“…Desiccation‐avoiding plants, on the other hand, could have high hydraulic conductivity between the xylem and the phloem, because they control the declining xylem water potential by early stomatal closure. These hypotheses are supported by our observation of large storage tissue surrounding the phloem in piñon pine (Figure S2) and the branch‐scale observations of Malone et al (), which suggested higher hydraulic conductivity in the radial direction in pine than in juniper. These hypotheses and all our findings, however, could still fit together if the turgor loss in pine phloem (Sevanto et al, ) was facilitated by turgor loss in the storage tissue rather than in phloem conduits, and the highest resistance to radial water flux in juniper was at the cambial zone rather than between phloem conduits.…”

In-Vivo NMR Spectroscopy: A Powerful and Complimentary Tool for Understanding Environmental Toxicity

“…While low field NMRs suffer from reduced resolution and sensitivity, their low cost and portability make them ideal for field deployment with often nothing more than a power supply required for monitoring. Some examples, include a mobile NMR lab for leaf phenotyping in the field [ 180 ], a portable sensor for monitoring water and sap flow [ 181 ], a device to detect water content in trees [ 182 , 183 ], fast field cycling NMR in plant leaves [ 184 ], as-well as lipid and metabolites profiling in seeds [ 185 ]. Advancement in technologies such as dynamic nuclear polarization in combination with low field NMR [ 186 ], and zero/ultra-low field NMR with optical detection [ 187 ] offer potential for huge increases in sensitivity that would advance low field NMR into a powerful tool for in-vivo analysis and monitoring.…”

Drought impacts on tree phloem: from cell-level responses to ecological significance

“…For trees, the model used might vary between the 'semi-permeable phloem' and models in which conduit walls are non-permeable with loading and unloading zones where material exchange occurs, as well as the degree to which the model can be modified (Sevanto et al 2018). However most of the conclusions about trees seem to be speculative or hypothetical because of a lack of empirical evidence (Sevanto 2014;Malone et al 2016;Sevanto et al 2018). Furthermore, there are many open questions concerning the conduit wall permeability, conduit location in relation to other cell types in the phloem, as well as the relevance of these anatomical features for phloem function under environmental stress (De Schepper et al 2013;.…”