Visualization of freezing progression in turfgrasses using infrared video thermography

Freezing injury can be a significant problem in turfgrasses. Understanding how freezing develops and ramifies throughout the plant could assist in the development of improved management or screening processes for cultivar improvement. The development of freezing injury is not well understood due partly to lack of technology to view freezing origin and progression of whole plants in real time. Perennial ryegrass ( Lolium perenne L.) and supina bluegrass ( Poa supina Schrad.) plants were incubated in either cold‐acclimating or nonacclimating temperatures. Droplets containing ice‐nucleating bacteria ( Pseudomonas syringae ) were placed on turf leaves, crowns, and roots. Plants were then subjected to progressively decreasing freezing temperatures in a controlled environment. An infrared thermal imaging radiometer (camera) was used to view ice initiation and propagation in whole plants in real time. Freezing always originated in roots, spreading acropetally and basipetally throughout connecting root tissues until it contacted the crown. Freezing was slow in the crown, then occurred rapidly upwards into shoots, then leaves. The time (i.e., temperatures) required for freezing was similar between the two species of nonacclimated plants. In acclimated plants, supina bluegrass roots froze earlier than roots of perennial ryegrass, though freezing times were similar for crown and leaf tissues. Ice‐nucleating bacteria did not incite freezing of turf tissues. The project demonstrated the utility of infrared imaging for detecting freezing events in whole turfgrass plants. Results suggest that root tissue in the vicinity of the crown can be a source of ice which propagates into the crown and kills the plant.