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Arizona's record heat is even killing saguaros

Arizona's saguaros are wilting in the record-breaking heat wave. An expert says the hot nights are ruining the cacti's photosynthesis process.

PHOENIX — The record-breaking heat wave scorching Arizona is also scorching the state's famous saguaro cacti.

Temperatures have been above 110 for 28 days straight.

“They literally can't function," Kimberly McCue with the Desert Botanical Garden said. "The way I describe it is, they start to suffocate.”

McCue said the long stretch of temperatures puts strain on the cactus, but it's not the main culprit. What hurts the cacti most is the overnight temperatures, which haven't dropped below 90 degrees in weeks. 

McCue said cacti use photosynthesis to convert sunlight to energy, as all plants do, but they do it differently than other plants. McCue said cacti split their photosynthesis process between day and night. At night, they open "pores" to take in carbon dioxide to convert into oxygen. 

But with the warm temperatures at night, that means the cacti lose water while doing this.

"At a certain temperature for a certain length of time, they just can't do it anymore," McCue said. 

McCue said the warning signs are fairly obvious. 

If a saguaro is leaning in one direction, it's probably not doing well. If it's squishy or soft to the touch, that's another warning sign. And if it's turning a yellowish color, it's being baked in the sun more than it can take. 

McCue said the Desert Botanical Garden can try to put shade cloth over some of its plants to protect them from the sun, but saguaros can stand 20 to 30 feet tall. There's not much they can do for them. 

“If that plant is really starting to shut down, doesn't matter how much water you pour on them, they won't be able to take it up and do anything with it," McCue said. 

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