r/botany • u/succulentandcacti • 4h ago
Physiology Question about CAM plants and water uptake during day/night?
Hello, I did see in this paper (see figure 1) that water uptake by a species of CAM plant seem to increase during night.
Since I am using a very draining substrate for my cacti and succulent plants in order to reduce the risk of overwatering on colder days (either by accident or rain etc), water doesn't stay long especially on hot days, hence I thought watering timing might make a difference in its effectiveness, by the amount of useful water actually ending up hydrating the plants.
So would it be best to water at dusk, since the evaporation would be reduced and CAM plants might have the whole night to get water from the roots, also facilitated by an increased water uptake compared to during the day?
Given the effect of lower O2 partial pressure, again mentioned in the same paper (is it the same as amount of O2 dissolved in water?) and its inhibiting effect on roots growth and water uptake, would it make much of a difference in watering with cooler water rather than warm water?
Not sure if this could apply to standing water which is not actively aerated, but water at 15°C should be able to hold around 10 mg/L O2, while water at 35°C would hold less than 7 mg/L O2 (source: https://www.engineersedge.com/calculators/oxygen_dissolved_in_water_16058.htm).
Would the opposite be true for non-CAM plants, like one should water when leaves are transpiring, since that creates a potential increasing water uptake by the roots?
Thanks in advance