Nomad blackboard: Cacti
1. Introduction
Cacti are one of the most fascinating plants in the world. They survive in the driest conditions as well as in a humid tropical climate. This text will inform about the cactus itself, how it can survive the drought and about the potential of cacti for the future in terms of climate change.
2. General information about cacti
Cacti (bot. Cactaceae) belong to the order Caryophyllales. The cacti family consists of nearly 2000 species and all live, with one exception, in North, Central, and South America, but are most common in the southwestern United States of America, as well as in Mexico. Cacti can survive in arid regions as well as humid and even tropical climates.
Cacti have a succulent stem, spikes instead of leaves, and short, fibrous roots. Most cactus species are considered an evergreen shrub while some are considered a tree or geophyte.
The height of a cactus ranges from one centimeter (Blossfeldia liliputania) to fifteen meters (Carnegiea Gigantea). Its annual growth can reach up to one meter.
Some cacti can live more than 200 years, while other species live only about 15 years.
3. How does a cactus survive a drought?
Cacti have adapted perfectly to survive in an arid climate.
One of the most important adaptations of a cactus is that it has spines instead of leaves which are modified leaves because normal leaves would lose too much water through evaporation.
Since the leaves are usually responsible for photosynthesis, the stem of the cactus is now responsible for photosynthesis, but even this is adapted to survive a drought. The cactus uses stomata in the stem to let in the carbon dioxide that is needed for photosynthesis. Stomata are small pores that open at night. While they are open, water can flow out of the cactus.
Therefore, the stomata only open during the night when it is colder, and less water can evaporate (crassulacian acid metabolism – CAM). Also, cacti have fewer stomata than normal plants. Cacti have between 15 and 70 stomata per square millimeter, while normal plants have more than 100 stomata per square millimeter, according to authors Arthur Gibson and Park Nobel in their book The Cactus Primer.
Cacti are covered with a thick, waxy cuticle that keeps water inside the cactus and prevents it from evaporating.
Inside the cactus, the parenchyma tissue can store a lot of water. Cacti can even expand to store as much water as possible. Ribs on the outside of a cactus prevent the cactus from breaking when it expands.
Cacti can absorb water through their superficial, fibrous roots from the soil. Also, small roots can grow as soon as it rains.
4. The future potential of cacti in terms of climate change
As mentioned before, cacti are extremely hardy plants and recent studies even showed that cactus pears are a drought-resistant crop that can be used for sustainable food and even fuel. Cactus pears are known to use 80% less water than traditional crops.
An American company, for example, uses cacti to produce flour and processes its waste into biofuel.
This is a great opportunity for Mexico and the whole world because most cacti grow in Mexico and because the climate is getting drier and hotter every year, many original crops will not survive, but the cacti will survive.
5. Conclusion
Cacti can survive in extremely dry conditions because they lose almost no water through evaporation, they absorb water through the roots in the soil, and because cacti can store a lot of water in the parenchyma tissue.
Their ability to survive drought has become more relevant as climate change has led to more droughts. A company in Mexico uses cacti as a crop to make flour and uses the waste from this production to produce biofuel.
6. Sources
https://www.hunker.com/13427935/characteristics-of-a-cactus
https://www.necps.org/unveiling-the-secrets-behind-cactis-drought-resistant-adaptations/
https://extension.umn.edu/houseplants/cacti-and-succulents
https://www.pflanzen-steckbriefe.de/sonstige/kaktus-steckbrief
https://www.bbc.com/future/article/20200521-mexican-cacti-a-sustainable-biofuel-from-the-desert
