Browsing by Author "Christensen-Dalsgaard, Karen"

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    Effect of soil conditions on the mycorrhizal colonization of Cannabis sativa
    (2020) Rayner, Lyndsay; Christensen-Dalsgaard, Karen
    Arbuscular mycorrhizal fungi (AMF) often display a beneficial relationship with plants by increasing water and nutrient availability, as well as mitigating various environmental stressors. This symbiosis, therefore, has the potential to be an effective and sustainable agricultural tool for improving plant health and yield. However, it is largely unknown how AMF interacts with and affects industrial hemp (Cannabis sativa). The present study aimed to assess how colonization of AMF may be affected by the variety of hemp or soil properties, namely pH. Plants were grown in a controlled greenhouse setting using natural field soil from an experimental farm in Vegreville, Alberta, Canada. In order to assess colonization, root samples from a minimum of seven plants per treatment were cleared, stained, and prepared for quantification using a standardized field of view method. Values are represented as the number of fungal vesicles per root volume (vesc/mm3), with averages generated for each treatment and then analyzed with a two-way ANOVA, a two-sample t-test, and descriptive statistics. Although it is still unclear which soil factors most strongly influence colonization, the observations and data from this study will be valuable for future research and aid in filling the knowledge gap regarding C. sativa and AMF.
  • Thumbnail Image
    Item
    Effects of NaCl and CaCl2 salinity stress on the germination, seedling and root morphology of Dalea candida
    (2020) Tonsi, Brittany; Christensen-Dalsgaard, Karen
    Calcium chloride (CaCl2) and sodium chloride (NaCl) are commonly used de-icing agents that result in saline-contaminated soils. Little is known about the effects of CaCl2 on plant germination, growth, and development. The purpose of this study was to compare the effects of CaCl2 and NaCl on germination and true leaf development of Dalea candida, a native legume of central North America. We further examined comparative effects on root growth and morphology at the initial germination phase. We used a controlled growth experiment consisting of various concentrations of NaCl (62.5mM and 125mM) and CaCl2 (31.25mM and 62.5mM) in soil and Petri dishes. While both salts exhibited negative trends, CaCl2 had less of an effect on the germination rate (64% at 31.25mM); however, aboveground true leaf development was stunted. NaCl at 62.5mM and 125mM exhibited a significantly lower mean root length and wider mean root diameter relative to comparable concentrations of CaCl2. Furthermore, only NaCl treatments significantly inhibited root hair presence. Our results indicate that while CaCl2 had less of a negative effect on initial germination, both salts stunt aboveground growth and development of D. candida seedlings via different mechanisms.
  • Thumbnail Image
    Item
    Effects of salinity stress on the germination, survival, and legume-rhizobial symbiosis of native legume Dalea purpurea
    (2020) Baran, Nicklas; Tonsi, Brittany; Christensen-Dalsgaard, Karen
    Soil salinity poses a major challenge for oil sands reclamation in Alberta. Sodium chloride is an abiotic stressor that negatively affects plants physiologically causing a need to identify native plant species capable of surviving and improving the soil conditions of these sites. Dalea purpurea (Fabaceae) is a promising candidate for oil sands reclamation, but no research has been done to assess its salinity tolerance and the effect of salinity on its Rhizobial symbiosis. In the present laboratory study, we subjected D. purpurea seedlings to pre-germination conditions of 0, 25, and 50mM NaCl, in the presence and absence of Rhizobial symbionts. We found a significant decrease in germination success and post-germination survival as a result of salinity with salt-sensitivity varying among individuals. Surviving individuals in salinity treatments displayed growth comparable to control treatments. Salinity did not affect nodulation, but significantly reduced nodule volume by 56% at 50mM NaCl. While nodule health of the species is negatively impacted by salinity, the species may be useful in salinity reclamation due to the presence of salt-tolerant individuals. This is the first study to consider the utility of native legumes and their rhizobial symbionts for the reclamation of saline oil sands sites.
  • Thumbnail Image
    Item
    Experimental culling of minnows suppresses cyanobacterial bloom under low-nutrient conditions
    (2019) Stuparyk, Blake R.; Graham, Mark; Cook, Jenna; Johnsen, Mitchell A.; Christensen-Dalsgaard, Karen; Vinebrooke, Rolf D.
    Cyanobacterial blooms in lakes of low nutrient status are recent ecological surprises. Culling of planktivorous fish may help suppress phytoplankton blooms via a trophic cascade effect. To test this hypothesis, we conducted a 90-day experiment adjacent to a shallow oligomesotrophic lake increasingly beset by midsummer cyanobacterial blooms in the presence of high abundances of minnows and sparse herbivorous zooplankton. The single-factor (± three spottail shiners, Notropis hudsonius) experimental design was replicated 10 times for a total of twenty 1200 L capacity mesocosms. Contrary to the trophic cascade hypothesis, minnow removal decreased the abundance of bosminids capable of grazing cyanobacteria. Nevertheless, removal of the minnows significantly both suppressed phytoplankton biomass and offset the development of cyanobacteria, such as Gloeotrichia echinulata. Lower concentrations of phosphorus and nitrogen in the fishless relative to stocked mesocosms best explained these differences in the phytoplankton community. Our findings highlight how fisheries management practices that enhance minnow populations in lakes of low productivity may inadvertently contribute to cyanobacterial blooms through increased nutrient cycling.