College of Agriculture & Natural Resources Department of Plant, Soil and Microbial Sciences

KAILEY MILLER: Final Thesis Defense Crop and Soil Science

March 18, 2025 1:00PM - 2:00PM 1-2pm

Plant and Soil Sciences Building room A271

Identifying Physiological Mechanisms and Winter Preparatory Strategies to Reduce Winterkill in Grass Species

Members of the Examining Committee and their Department:

1. Dr. Emily Holm – Plant, Soil and Microbial Sciences

2. Dr. Eric Olson – Plant, Soil and Microbial Sciences

3. Dr. Maninder Singh – Plant, Soil and Microbial Sciences

4. Dr. Randy Beaudry – Department of Horticulture

The seminar precedes the examination, at the time above

ABSTRACT

Winterkill stresses, such as ice encasement, waterlogging, and winter desiccation can threaten the survival and productivity of turfgrass species like annual bluegrass (Poa annua) and grass crops like winter wheat (Triticum aestivum). Ice encasement and waterlogging can cause hypoxic or anoxic conditions that trap toxic gases and metabolites that can damage plant structures. Winter desiccation can occur due to exposure to dry or frozen conditions in the soil and low humidity in the air. Since major knowledge gaps exist regarding how to better manage grasses during winterkill conditions and how grasses respond to these winter stresses, this dissertation explores four major objectives. The first two objectives investigate management strategies to promote winter survival including: 1) how fall mowing height changes influence annual bluegrass putting greens following field winter conditions or simulated ice encasement and 2) the influence of seeding depth and coleoptile length on photosynthetic efficiency during cold acclimation and ice encasement survival in winter wheat. The other two objectives investigate physiological responses to winterkill conditions: 3) photosynthetic imaging of winter wheat regrowth after ice encasement or winter desiccation and 4) the combined effects of ice encasement and waterlogging stress on the physiological responses of winter wheat. The first objective results indicated that canopy parameters generally decreased during fall and increased during the spring, with higher mowing heights typically resulting in higher canopy parameters in the fall. Under controlled growth chamber conditions, higher mowing heights led to a greater recovery in green cover percentage and faster recovery after 20 and 40 days under ice encasement compared to the lower treatments in the first year, with prolonged durations of ice encasement decreased total nonstructural carbohydrates. The second study results indicated that plants seeded at a deeper depth exhibited a higher photosynthetic efficiency during acclimation, while those seeded at the shallow depth had improved leaf area, reduced oxidative damage, and enhanced biomass and yield after ice encasement. The third experiment demonstrated that photochemical health parameters such as nonphotochemical quenching (NPQ) and its components, energy-dependent quenching (qE) and photoinhibition (qI), were effective in distinguishing between surface ice layer and winter desiccation stresses and may serve as valuable tools in future studies aimed at enhancing stress tolerance. The fourth and final study found that the combination of ice encasement and waterlogging stress negatively impacted growth characteristics and elevatedoxidative stress. This research enhances the understanding winterkill stresses on winter wheat and turfgrass and provides valuable insights for management strategies of these environmental challenges.