When a saguaro starts to produce arms, it depends more on its height than on its age. More arms equate to more flowers and fruit, which aids in the cactus’ ability to reproduce. (Image credit: Stina Sieg/KJZZ)
At the Desert Botanical Garden, where Raul Puente-Martinez is the curator of live collections, Kevin Hultine is a plant physiologist. (Image credit: Jackie Hai/KJZZ)
PHOENIXSaguaros are towering sentinels with shapes that are recognizable yet delightfully, wildly diverse. They are an enduring symbol of the American West. These cactuses, which can grow to a height of 60 feet, weigh more than 2 tons, and have a lifespan of more than 200 years, captivate both locals and tourists in Arizona.
But why are saguaros special? Why only in the Sonoran Desert do they flourish? Why do some people develop multiple arms while others don’t?
Researchers are working hard to discover the mysteries of the slowly expanding Carnegia gigantea.
Dozens of 2-year-old saguaros are growing in an artificial white-yellow light bath in a small, windowless chamber in the Life Science Center of Arizona State University in Tempe.
Martin Wojciechowski, an evolutionary scientist at Arizona State University who cultivated the cacti from seed, stated that they “look like just green thumbs rising up out of the earth with, you know, tons of spines.” They first appear as “diamond-shaped green blobs,” he claimed, from tiny black seeds.
These saguaros are unique because they are descended from SGP-5 F1, or Saguaro Genome Project, cactus No. 5, the first filial generation, which was the first saguaro whose entire genetic makeup had been decoded. No. 5 developed on Tucson’s Tumamoc Hill until it was destroyed by a monsoon storm.
Wojciechowski and his coworkers want to discover the mysteries of the saguaros. Only the Sonoran Desert, often below 4,000 feet in elevation, which encompasses parts of northern Mexico, Arizona, and a small portion of California, supports their growth. There are two rainy seasons in the Sonoran, and summer monsoon rains are regarded to be essential for saguaro growth.
Wojciechowski stated, “We would like to understand how and when those adaptations to life in a hot, dry climate emerged.
These genes may also provide explanations for how the saguaro acquires its characteristic form. But there are some things that are already known to scientists.
They are aware of which way is up, according to Wojciechowski. They position themselves in a somewhat vertical direction since they are aware of which way is downward.
Saguaros’ shallow, widely dispersed roots and the tips of their stems are where they derive their growth. Rainfall causes a saguaro’s diameter to change, much like an accordion. They enlarge when there is more water present and vice versa.
“The chance is that you may persist for a long time if you have a huge big stem, plenty of store, but you grow really slowly,” said Kevin Hultine, a plant physiologist at the Desert Botanical Garden in east Phoenix, where more than 1,000 saguaros stand.
According to estimates, saguaros can live for 200 years or more. How much water they can store is one of the keys to surviving in the desert.
Although some saguaro cacti never develop arms, the first saguaro arms appear when the cactus is around 10 feet tall. Contrary to popular assumption, the arms don’t appear at a certain age, according to Hultine. The saguaro’s growth rate is influenced by its location and the water supply.
Hultine put the weight at 250 pounds and added, “I would assume that, right now, it’s probably storing 30 to 40 gallons of water just in that arm.