Main conclusion: Quantitative neutron imaging is a promising technique to investigate leaf water flow and transpiration in real time and has perspectives towards studies of plant response to environmental conditions and plant water stress. The leaf hydraulic architecture is a key determinant of plant sap transport and plant-atmosphere exchange processes. Non-destructive imaging with neutrons shows large potential for unveiling the complex internal features of the venation network and the transport therein. However, it was only used for two-dimensional imaging without addressing flow dynamics and was still unsuccessful in accurate quantification of the amount of water. Quantitative neutron imaging was used to investigate, for the first time, the water distribution in veins and lamina, the three-dimensional venation architecture and sap flow dynamics in leaves. The latter was visualised using D2O as a contrast liquid. A high dynamic resolution was obtained by using cold neutrons and imaging relied on radiography (2D) as well as tomography (3D). The principle of the technique was shown for detached leaves, but can be applied to in vivo leaves as well. The venation network architecture and the water distribution in the veins and lamina unveiled clear differences between plant species. The leaf water content could be successfully quantified, though still included the contribution of the leaf dry matter. The flow measurements exposed the hierarchical structure of the water transport pathways, and an accurate quantification of the absolute amount of water uptake in the leaf was possible. Particular advantages of neutron imaging, as compared to X-ray imaging, were identified. Quantitative neutron imaging is a promising technique to investigate leaf water flow and transpiration in real time and has perspectives towards studies of plant response to environmental conditions and plant water stress.
Bibliographical noteFunding Information:
Acknowledgments This work was supported by the European commission under the 7th Framework Programme through the ‘research Infrastructures’ action of the ‘capacities’ Programme, nmI3-II grant number 283883. Thijs Defraeye is a postdoctoral fellow of the research Foundation—Flanders (FWO) and acknowledges its support. Financial support by the research Foundation—Flanders (Project FWO g.0645.13) and KU leuven (Project OT 12/055) is also gratefully acknowledged. The experiments were carried out at the IcOn beamline (sInQ: swiss spallation neutron source) of the Paul scherrer Institute, Villigen, switzerland. We would like to acknowledge the contributions and support of the Paul scherrer Institute IcOn support team.
- Flow dynamics
- Neutron imaging