Re: Do CAM plants exhibt a defense mechanism when exposed to a change?

Unless the plants were exposed to freezing temperatures on their trip from the greenhouse, the transport period probably is not responsible. Did you determine if the stomates were open in the light or dark for your jade plants (Crassula argentea)? A simple test for stomatal opening would be to place a potted plant, with a plastic bag around the pot, in continuous dark and an identical one in continuous light and determine the transpirational weight loss of each over several days. The CAM species most often used for CAM (Crassulacean Acid Metabolism) experiments seems to be Devil's backbone (Kalanchoe daigremontiana) which forms little plantlets on the edges of its leaves.

Was the light level during the experiment high enough to support a decent level of photosynthesis?

Another possible explanation is that some CAM species are facultative and can revert to non-CAM photosynthesis when the environment is less harsh. CAM is an adaptation to reduce transpiration under hot dry conditions. CAM is favored by hot days with high light, cool nights, and dry soil. Under cooler temperatures where water is plentiful, as in a greenhouse, there is no advantage for the plant to use CAM. Using the CAM pathway "costs" the plant energy in order to save it water. If water is not limiting, then it is more efficient not to use the CAM pathway.

References:
Friend, D.J.C. 1990. Plant eco-physiology: Experiments on Crassulacean acid metabolism, using minimal equipment. American Biology Teacher 52: 358- 363.

Salisbury, F.B. and Ross, C.W. 1985. Plant Physiology. Belmont, CA: Wadsworth.