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California's endangered redwood trees are some of the most spectacular flora on the planet. They can live for 1,800 years and grow as high as 360 feet. But as awe-inspiring as the average redwood is, there are a handful that really capture the imagination: the albino redwoods.
Scattered throughout the redwood range—which stretches along the north Pacific coast—are redwoods with pure white branches and foliage. Some have just a few white branches, others are half green and half white, and a few are completely white from trunk to top.
Besides their striking appearance, these trees are mysterious because they lack chlorophyll, the protein plants use to convert sunlight into food. Chlorophyll also gives plants their green color, but these albino redwoods have no color, and no chlorophyll. They shouldn't be able to exist.
"They should die, but they don't," said Zane Moore, a graduate student at the University of California Davis who studies albino redwoods.
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In the summertime, when the trees are growing, each branch gets basically cut off from the rest of the tree. They're on their own. Without any chlorophyll, these white branches can't produce their own food, so they should die and fall off. But with the albino redwoods, this doesn't happen.
Very little is understood about these trees. They're very rare, so they haven't been extensively studied. When Moore began studying plant genetics at university, he knew it could tell him a lot about these trees, which had fascinated him since he was a teenager.
"I first learned about them in 2008 and I said I want to find one of these things and see if they're as weird as everyone said they were," Moore told me. "I kind of used hints to find one on my own."
Working with Tom Stapleton, an arborist and one of the few experts who has spent time researching these trees, Moore began tracking the location of each of the 441 albino redwoods. When they plotted out that data, the noticed something striking: all of the albinos were found on the outer reaches of the redwood range. Due to the soil and other environmental conditions, there are some areas where the redwood range just kind of tapers off and the trees don't grow beyond that point. And that's exactly where most of these albino redwoods kept showing up.
Moore and Stapleton then began testing the soil in these borderlands to try to figure out if they were different from the heart of the redwood range. Again, they found some noticeable differences: the soil in these transition zones contained higher levels of heavy metals, such as nickel, copper, and cadmium. When Moore tested clippings from the albino redwoods and compared them to clippings from the green trees, he found significantly higher levels of these metals in the albino trees—twice as much, on average.
In a green tree, levels of metal this high would be deadly, Moore explained, because they poison the pathways making chlorophyll, making it impossible for the tree to photosynthesize.
"It's kind of like heavy metal poisoning, a human example would be lead poisoning," Moore said.
But, again, the albino trees don't make chlorophyll, so there's nothing for the metals to disrupt. Instead, Moore thinks these trees might have a symbiotic relationship with their green limbs. The white limbs suck up all these toxic metals and, in exchange, the healthy green limbs share food with the chlorophyll-deficient white branches.
"It's like an investment, that's a good way to look at it," Moore told me. "If you think about it from a plant perspective, if the plant invests a little bit of its sugars into creating this white useless structure, and that useless structure actually worked, actually allows the plant to grow quicker, then the plant would want to do that again. And year after year grow that out and that's how you get these big albino branches."
Moore is currently running experiments to test out this hypothesis, and he's excited to see if there's good evidence that this is what allows these strange trees to exist in the first place. But even if he's wrong, it will lead to a deeper understand, and hopefully inch us closer to cracking the case.
"It's literally a matter of time before we have a good idea of what's happening," Moore said.