Page 115 - PC2019 Program & Proceedings

PLANT CANADA 2019

S15. Tissue-specific changes in the apoplastic and intracellular proteome during sub-zero
acclimation of winter wheat and rye crowns
1
2
Willick, I. ; M. Uemura ; B. Fowler ; K. Tanino 1
1
1 University of Saskatchewan
2 Iwate University
Cold-acclimated winter cereals acquire an additional 2°C to 5°C increase in freezing survival when
exposed to soil temperatures of -3°C for 3 d. This additional acquisition of cold hardiness is known as
sub-zero acclimation. Previous crown studies have observed the vascular transition zone (VTZ) to have a
higher freezing sensitivity than the shoot apical meristem (SAM). The mechanism behind the differential
freezing response and how sub-zero acclimation enhances tissue-specific freezing survival is not fully
understood. Using the current superior freeze resistant winter wheat (Triticum aestivum L.) ‘Norstar’ and
more winter hardy ‘Puma’ rye (Secale cereale L.) as a model, freezing properties and proteome analysis
of field grown sub-zero acclimated crown tissues were contrasted to identify species-specific mechanisms
of freezing survival. In sub-zero acclimated crowns, patterns of injury were examined with tetrazolium
chloride vital stain and compared to whole plant recovery. Cold and sub-zero acclimation resulted in
distinct SAM and VTZ proteomes. In the sub-zero acclimated crowns, greater accumulation of anti-freeze
proteins in the VTZ and proteins enhancing desiccation tolerance in the SAM improved resistance to
freezing in rye compared to wheat. Differences in the intracellular and apoplastic proteomes will be
discussed. Identification of protein markers associated with field acclimation will be useful to breeders’
intent on selecting for and improving the freezing survival of winter wheat.

Ian Willick (ian.willick@usask.ca)

S16. Thriving or barely surviving: examining heat-stress induced mortality of tamarack under
extreme climate conditions
*
Murphy, B. ; D. Way
University of Western Ontario

As temperatures and greenhouse gas emissions increase, so will the frequency of climate-induced tree
mortality events. This will affect the future functioning of northern forests and could impact global carbon
cycling. While interactive effects of drought and heat stress have been studied, there is little known about
the impact of heat stress alone on tree mortality. We grew tamarack (Larix laricina) under ambient (400
ppm) and elevated (750 ppm) CO2 concentrations combined with ambient (average London, ON
temperatures), ambient +4 ˚C, and ambient +8 ˚C growth temperatures to examine seedling carbon fluxes
to investigate whether high growth temperatures may lead to carbon limitations and mortality. Growth at
+8 °C warming led to considerable mortality in the ambient CO2 treatment, but not the elevated CO2
treatment. We first evaluated carbon balance parameters of healthy seedlings across all six treatments.
There was no acclimation of photosynthesis, but respiration decreased with increasing growth
temperature. Root respiration measured at a standard temperature did not differ across the treatments. We
examined carbon balance parameters between healthy and dying seedlings in the ambient CO2 /+8 ˚C
treatment and found there was trend of a lower ratio of net CO2 assimilation rate (Anet) to dark respiration
rate (Rdark) in dying seedlings (p=0.0931). Further investigation should provide insight into whether
carbon limitations are the cause of observed seedling mortality under high growth temperatures

Bridget Murphy (bmurph26@uwo.ca)

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