Mechanisms Controlling Day/Night Changes in CAM Tissue Volume, With a Focus on the Kansas Cactus, Opuntia macrorhiza

Abstract

Day/night changes in organs volume of Crassulacean Acid Metabolism (CAM) plants have been observed. The objective of this study is to determine the most important mechanism that controls day/night changes of organ thickness in CAM plants. In this study, day/night changes in organ volume and morning and evening acidities of organs were measured. The focus was on the CAM species Opuntia macrorhiza under different conditions. Mechanisms that may explain these day/night changes in organs volume of CAM plant could be day/night changes in internal CO2 pressure, day/night changes in water content or day/night changes in temperature. Pervious study suggested that day/night changes could be due to internal CO2 pressure inside tissues or water content. This study confirmed these two mechanisms and has added a new variable which is day/night changes in temperature.