Cacti, known for their thick, spiny skin and sharp thorns, are surprisingly resilient. They can survive in places with little to no soil or rain. To survive these conditions, cacti must have adapted ways of finding water that other plants cannot access.
The most common adaptation is taking in water through their roots. Cacti have shallow root systems that grow close to the surface of the soil, giving them access to any standing surface water.
Their fleshy leaves also store moisture and keep it available even during periods of drought. Drip irrigation is an effective way for those who wish to attempt growing cacti with just water instead of soil.
Another important factor for cactus survival without soil is the massive amount of oxygen they consume from the air around them, which keeps them healthy even without much direct light from the sun.
In addition, all succulent plants like cacti contain special mechanisms, often referred to as crassulacean acid metabolism (CAM) pathways, which allow them to maximize their use of carbon dioxide and minimize that used for making energy from photosynthesis leading to the conservation of water in dry climates.
Finally, cacti can draw up moisture from tiny droplets found on rocks and other objects created by condensation or morning fog creating an environment suitable for their growth even when there’s a severe lack of water otherwise. All these adaptations together make it possible for the hardy cactus species to thrive in an environment consisting only of water!