Malda G., Suzán H., Backhaus R., In vitro culture as a potential method for the conservation of endangered plants possessing crassulacean acid metabolism, Scientia Horticulturae, 1999, 81(1):71-87, doi: 10.1016/S0304-4238(98)00250-7
The paper compares micropropagation, growth and acclimatisation in Obregonia denegrii and Pelecyphora minima (Coryphantha minima in the publication). It includes shoot and somatic embryo formation, rooting, survival after transfer from culture and daily changes in titratable acidity. It discusses the significance of succulence and physiological variation for the propagation of threatened cacti. Gas exchange is cited from a separate study.