Cell wall: strong; supporting layer around the cell membrane in plant cells
The relationship between osmosis and aquaporins are usually found is some vital physiological functions like the water re-absorption in the kidney. It is even found in the secretion of the glands and airways. Also in the water hemeostatis in the brain. In this functions osmotic waters transports in aquaporins.
I am answering under the assumption that those are cacti in the desert. Well as we know, cacti are producers they have the ability to synthesize their own food using photosynthesis which is a process that converts solar energy into glucose “food”. It has the ability to be a good source to small animals with its fruits and seeds. An example is, some insects feed off the nectar from the cacti. A second reason is that cacti are carbon sinks meaning that they take in carbon dioxide. Just to familiarize you the formula for photosynthesis is CO2 + H2O + energy equals glucose + O2 . Without carbon dioxide none of it is possible. Without cacti, CO2 levels would increase leading to bad affects.