Goldstein G., Nobel P. S., Water Relations and Low-Temperature Acclimation for Cactus Species Varying in Freezing Tolerance, Plant Physiology, 1994, 104(2):675-681, doi: 10.1104/pp.104.2.675
The study compares water relations, sugars, mannitol, mucilage and ice formation in three opuntias. Analyses include material acclimated at day/night temperatures of 10/0°C, including plants historically identified as Opuntia humifusa.