bio

Crassulacean acid metabolism (CAM)

The same problem C4 solves, but separated in time rather than in space. The plant opens its pores at night, when the air is cool and damp and water loss is least, captures CO₂ and stores it as an organic acid; then through the whole blazing day it seals the pores shut and releases CO₂ from that acid store internally, behind a locked door. Cacti and pineapples run this way. It is the most extreme water-thrift strategy Earth plants ever devised — and the clearest evidence of how harsh the trade at the pore really is: some lineages rearranged their entire daily rhythm purely to spend less water.