Plant ecophysiologists are concerned with understanding how plants sense and respond to environmental cues. Our group seeks to address these issues in natural and controlled terrestrial ecosystems, while assessing the resilience and adaptive capacity of these systems to environmental change.
Why study plant cold hardiness in a warming world? One of the most pressing concerns in biology is whether we can predict how plants growing in cool climates will respond to warming seasonal temperatures. Complex feedbacks such that the responses of crops to warmer conditions could either slow or accelerate production. Our lab addresses this uncertainty by studying the physiological responses of crops and related species to shifting temperatures and water stress.
Major research questions
Can we manipulate ice nucleation in plants to mitigate frost injury?
Frost-sensitive species have a limited ability to tolerate ice formation in their tissues. These species avoid ice formation by supercooling (undercooling) below 0°C to avoid ice formation. Conversely, frost-tolerant species have adapted to cope with prolonged ice formation in their tissues and use this mechanism to survive frost events. Injury in these tolerant species arises from the degree of freeze-dehydration of cells and subsequent rehydration during a thaw. The presence of ice nucleation active bacteria can prove beneficial for the establishment of ice formation in freezing tolerant plants and devastating to the survival of frost-sensitive species. In the past we explored how winter cereal crowns have developed a tissue-level ice formation strategy to protect critical meristem tissues and survive exposure to sub-zero temperatures.
Our current research in grapes (Vitis spp.) characterizes how different under-vine soil amendments aimed at improving plant nutrition could influence spring canopy temperatures. Bare soil under vines promotes the capture of thermal heat during the day and its release overnight. The use of dense undervine cover crops and mulches could result in cooler canopies that are more susceptible to frost injury. Our research will monitor vine temperatures, characterize organ-specific differences in microbiomes, and employ infrared thermography to better characterize how ice nucleation persists through freezing avoidant floral buds.
Two exothermic peaks were observed using infrared video thermography in haskap leaves cooled to -4°C. The first exotherm (orange) propagates through bulk water in the xylem over a period of seconds. A second freezing event (blue) occurs over a period of minutes and propagates through the lamina in a wave like pattern.
Can we optimize management strategies to mitigate the loss of cold hardiness?
Our program is currently investigating the influence of Fall pneumatic defoliation on apple orchards. Defoliation of apple trees two weeks before harvest can enhance red blush by exposing the fruit to additional light and cooler night temperatures. In addition to their role as carbohydrate-producing organs, leaves are also receptors for photoperiodic and temperature stimuli required to initiate acclimation. Removal of too many leaves can have the unintentional effect of reducing the overall cold hardiness of the plant.
We are also studying the effects of fall tillage in vineyards. A movement towards fall tillage as compared with tillage in the spring because soil moisture is generally below field capacity, there is less potential for soil compaction, and soil temperatures are more suitable for tilling. However, tillage in the fall can disrupt surface roots resulting in injury to the vine as the vine and buds cold acclimate and enter dormancy.
Funding is generously provided through the Agricultural Climate Solutions – Living Labs Project, Grape Growers Association of Nova Scotia, and the Nova Scotia Fruit Growers Association. Projects are conducted in collaboration at the vineyards and orchards of producers in the Annapolis Valley, NS.
In-row alternative tillage (left) and non-tillage control (right) treatments applied to a test vineyard in the Annapolis Valley (Nova Scotia, Canada).
Will silicon fortification enhance the tolerance of grapevines to biotic and abiotic stress?
Growers in Nova Scotia grape growers recognize the need for an effective nutrient management program but have typically minimized inputs because of known vigour issues in hybrid varieties. Development of sustainable practices for Eastern Canada needs to consider cool soils early in the year that reduce nutrient uptake. Furthermore, commercial fertilizers are not permitted in organic production systems.
Our research assesses whether foliar silicon (Si) amendments reduce injury from abiotic stress and insect feeding damage. The application of Si-based amendments has become a common agricultural practice to boost the bioavailable form of Si (monosilicic acid, H4SiO4) to prime plants and enhance resiliency in response to insect feeding damage, pathogens, temperature, humidity or salinity stress. Bioavailable H4SiO4 is absorbed from the soil by root cells or from foliar applications by stomata, hydrathodes, and cracks on the leaf surface. Upon uptake, H4SiO4 polymerizes into an immobile silica gel (SiO2·nH2O). We are interested in assessing whether the development of a Si-cuticle double layer within the leaf tissue provides an enhanced physical barrier to environmental stressors. Our research incorporates various microscopy techniques and attenuated total reflectance (ATR) Fourier transform infrared (FTIR) spectroscopy to assess how modifications to the cuticular layer enhance the tolerance of a plant to temperature, dehydration or salinity stress.
Funding is generously provided by the Government of Canada.
What are the molecular mechanisms that induce cold acclimation?
Cool season plants cold acclimate when pre-exposed to fall environmental cues, undergoing a series of physiological and molecular modifications. Higher fall and winter temperatures will extend the growing season and delay fall senescence. This uncoupling of short-day length from cooler nighttime temperatures can disrupt the senescence of aboveground foliage and the induction of cold acclimation.
We aim to understand in switchgrass (Panicum virgatum) the molecular basis for the local adaptation of cold acclimation. Switchgrass is a perennial biofuel crop that has undergone limited breeding in the past. In particular, we are focused on the divergence between the northern upland and southern lowland ecotypes. Northern upland switchgrass is more cold hardy but produces less aboveground biomass as compared with the more southern lowland ecotypes. We will use RNA sequencing and physiological profiling to develop a more mechanistic understanding of how cool-season plants respond to rising temperatures. This work will identify novel traits of interest that can be used to identify populations with optimal biomass and cold hardiness traits
Current research in switchgrass is moving forward in collaboration with Dr David Lowry’s research group (Michigan State University). This research is supported by the Great Lakes Bioenergy Research Center and the US Department of Energy.
Drone image of switchgrass populations at Kellogg Biological Research Station (Hickory Corners, MI). Photo credit: Robert Goodwin.