Page 123 - PC2019 Program & Proceedings

PLANT CANADA 2019

S31. Spring into action: How warm air and cool soil temperatures influence nitrogen fixation and
physiological performance in green alder
*
Anderson, P. ; J. Markham
University of Manitoba

The short growing season and cold climate of the Canadian boreal forest can result in restricted amounts
of available soil nitrogen, limited overall plant growth and low ecosystem productivity. Nitrogen fixing
plants, which form symbiotic relationships with specialised bacteria, have an advantage in low nitrogen
environments, but are not widespread in the boreal. The reason for this is not well understood. It has not
been properly documented how nitrogen fixation and overall plant performance are impacted by seasonal
temperatures changes in the soil and air, especially in the spring when soil temperatures remain cool as air
temperatures increase. This study was conducted to examine how below ground (nitrogen fixation) and
above ground (photosynthetic) processes are impacted when soil and air temperatures differ. A lab
experiment using the woody, nitrogen fixing species Alnus viridis ssp. crispa (green alder) was
conducted. Soil was cooled to 10˚C, 14˚C and 16˚C (control) independently of shoot temperature at 22˚C,
over a period of 13 weeks. Cooler soil temperatures were found to inhibit nitrogen fixation and
photosynthesis during the growing period. Decreasing soil temperatures also resulted in significantly
lower chlorophyll content, growth rate, tissue weight and specific leaf area, compared to control plants at
time of harvest. This research will help us to further understand the role of nitrogen fixing plants in the
Canadian boreal and why their availability is restricted.

Paige Anderson (anders75@myumanitoba.ca)

S32. Influence of mycorrhizal mutualism and plant life history on the diversification of plant root
morphology and function
*
Shao, J. ; H. Maherali
University of Guelph

The root is an integral part of all vascular plants, which functions to anchor the plants, and to acquire and
transport soil water and nutrients to ensure plant survival, growth and reproduction. There is significant
variation in plant root functional traits such as plant root diameter, root hair density, and root branching
intensity, but no consensus on the mechanisms causing the diversification of plant root traits. We
hypothesized that plant arbuscular mycorrhizal (AM) fungal symbiosis, which has existed since early
ancestral land plants, could have co-evolved with plant root systems to help overcome challenges like
desiccation and nutrient limitation. One hypothesis is that plant responsiveness to AM fungi could covary
with root morphological traits. Alternatively, plant economic spectrum (PES) hypothesized that plant
roots could have evolved in a coordinated fashion with leaf functional traits, aligning with plant
ecological strategies involving maximizing productivity or conservation of resources. To test these
hypotheses, we examined the correlation between root traits, plant mycorrhizal responsiveness and leaf
functional traits among 34 populations of legume Medicago truncatula under high and low Phosphorus
environments. Plant shoot & root biomass, leaf chlorophyll, and root functional traits (root branching,
average root diameter, specific root length) were measured and analyzed, the results and their
implications will be discussed.

Jianfei Shao (shaoj@uoguelph.ca)

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