Sempervivum Photosynthesis
After reading the previous post, how do Sempervivum conduct photosynthesis? For much of the time Sempervivum are CAM plants as you may have guessed by now. The CAM mechanism lends itself to wide swings of temperature, dry conditions and copious amounts of sunlight, which is part of why Sempervivum, "live forever." The CAM process has 4 stages. Here is a general description of what goes on in each stage:
STAGE 1, Dark period---stomata open and take in CO2 which is fixed in the plant as malic acid.
STAGE 2, First 2 hours of light---stomata still open and taking in CO2, malic acid still being fixed in plant cells, then the stomata slowly close.
STAGE 3, Morning into afternoon---stomata are closed and plant breaks down malic acid to use the stored CO2 for photosynthesis. This is when CAM plants grow. Once all the malic acid is broken down and the stored CO2 is used up, we enter the next stage.
STAGE 4---afternoon until dark, after the plant uses the stored CO2, the stomata may open back up and the plant takes in CO2 and uses C3 photosynthesis for the remainder of useful light.
There are certain environmental conditions that experiments show Sempervivum do not use CAM, instead they act like C3 plants, complete with the greater water loss from having stomata open during the day.
So for the most part think of your Sempervivum like a storage battery, storing CO2 at night and using it during the day, but if not enough can be stored, or light levels high enough that it is used up quicker and the plant opens up its stomata in the afternoon, it opens itself up to much greater water loss, which is why it seems when growing Semps that they can take either heat, or alot of sunlight but not both. This is because it causes the semp to use up its CO2 faster and they open the stomata before the day has cooled and now lose alot of water to evaporation.
