Prof Daniel Holland, Prof Matthew Watson, Matt Rennie, Dr James Robinson and A/Prof Justin Morgenroth (University of Canterbury), Prof Mike Clearwater (Waikato University) and Abby van den Berg (University of Vermont)
Maple syrup is a high value commodity that is geographically restricted to regions of long, cold winters (i.e., north-eastern North America). However, there is evidence to suggest that sugar maples can produce sap in milder climates, such as New Zealand.
Sugar maple trees exude high volumes of sugar rich sap in spring, which is processed into maple syrup. The causes underlying maple sap exudation are poorly understood, although it is thought that repeated freeze thaw cycles create high stem pressures and hence sap flow.
The researchers used the high-speed imaging capability of the Imaging and Medical (IMBL) beamline to observe changes in gas filled vessels within the xylem of maple saplings throughout a freeze-thaw event. Analysing changes in these vessel embolisms helps to clarify the mechanisms of sap exudation, and the specific role freeze-thaw cycles play in the development of stem pressure.
The results to date support the idea that repeated freeze thaw cycles create the pressure needed for maple sap to flow. This information will help inform on the viability of establishing a maple syrup industry in the New Zealand climate.
References:
Robinson JA, Rennie M, Clearwater M, Holland DJ, van den Berg AK, Watson M. 2023. Examination of embolisms in maple and birch saplings utilising microCT. Micron. 168. https://doi.org/10.1016/j.micron.2023.103438
Robinson J, Rennie M, van den Berg AK, Clearwater M, Holland DJ and Watson M. 2025. MicroCT imaging of fibre water uptake in sugar maple (Acer saccharum) in response to freezing. Micron. 196-197. 103869. https://doi.org/10.1016/j.micron.2025.103869
Related research:
Reid S, Driller T and Watson M. 2020. A two-dimensional heat transfer model for predicting freeze-thaw events in sugar maple trees. Agricultural and Forest Meteorology. 294. 108139. https://doi.org/10.1016/j.agrformet.2020.108139
Related media:
https://ir.canterbury.ac.nz/server/api/core/bitstreams/b41e821e-bda8-413d-b614-4efe50f9c2e2/content
https://www.canterbury.ac.nz/news-and-events/news/nz-maple-syrup-mission-taps-into-hi-tech-imaging
https://www.canterbury.ac.nz/news-and-events/news/sweet-future-tapped-for-nz-maple-syrup-test
https://www.stuff.co.nz/science/106999983/nz-maple-syrup-industry-possible-and-promising
