Nobel P. S., Influence of Freezing Temperatures on a Cactus, Coryphantha vivipara, Oecologia, 1981, 48(2):194-198, doi: 10.1007/BF00347964
Experiments on Coryphantha vivipara var. deserti material from Nevada combine observations of stem temperature, survival and recovery of gas exchange with an analysis of ice formation. They examine changes in protoplast volume, the osmotic properties of sap and cell viability after frost. Gradually lowering the temperature at which the plants were kept increased cell tolerance as assessed by vital staining.