Nobel P. S., Hartsock T. L., Drought‐induced shifts in daily CO2 uptake patterns for leafy cacti, Physiologia Plantarum, 1987, 70(2):114-118, doi: 10.1111/j.1399-3054.1987.tb06119.x
The experiment compares daily CO₂ exchange in the leaves and stems of six leafy cacti during increasing drought. Three opuntioids showed a shift from predominantly daytime leaf assimilation to predominantly nocturnal assimilation, while total CO₂ uptake declined. The table includes separate day and night balances after 0, 7 and 14 days of drought.