Loik M. E., Nobel P. S., Freezing Tolerance and Water Relations of Opuntia fragilis from Canada and the United States, Ecology, 1993, 74(6):1722-1732, doi: 10.2307/1939931
The experiment compares freezing resistance in twenty Opuntia fragilis populations after acclimation under uniform conditions. The authors compare LT₅₀ values and water loss, showing large provenance differences and no simple relationship between these features.