Southwest Cacti Hide Roots from High Temperatures

The “living rock” cacti, Ariocarpus fissuratus, lives in one of the hottest environments on earth—the searing surface of the Chihuahuan desert in southwest Texas where temperatures can reach over 150°C, much warmer that the air temperature. In a new study published in the American Journal of Botany, scientists from Occidental College have discovered how this plant survives the near-lethal temperatures.  Simulating the heat of the desert with a Los Angeles rooftop, the scientists found that when the cacti are grown in soil with a rocky covering, similar to their natural habitat, they are more likely to survive, as the rocks cool the surface temperature. Cacti planted in sandy soil without rocks died. In both cases though, the cacti used root contraction to burrow deeper into the cooler ground as temperatures increased. However, one of the authors told ScienceDaily that the surface temperatures experienced by the cacti that survived were still near-lethal, implying that with a future of warmer temperatures, these resilient cacti may not fare well.