10 May 2012
They're known as "ghost trees," and for good reason: albino redwoods are extremely rare and nearly impossible to spot. There may be as few as 25 of these trees in the world, yet eight of them are at Henry Cowell Redwood State Park in Northern California.
These trees are not just pale: they're dead white, and their needles are limp and waxy - 'the exact color of a glow-in-the-dark star you might find in a kid's bedroom', says science journalist Amy Standen. A genetic mutation has prevented them from producing chlorophyll, and the result is that they're entirely unable to photosynthesize.
So how can a plant not only survive, but grow, without the ability to produce its food? "Without chlorophyll, they can't photosynthesize... The only reason that albino redwoods
survive at all is that they are connected at the root to a parent tree
from which they will suck energy for their entire lives," Amy Standen says. "It's like some 40-year-old who refuses to get a job, keeps eating his
parents' food and sleeping in his old bedroom. In the case of the
redwoods, this arrangement can last a century, or more - and no one
knows why." Or you could see these trees as vampires - surviving only by sucking life from others.
But this isn't just an intriguing insight into photosynthesis. The albino redwoods have a lot to tell us about the process of evolution.
Park ranger Dave Kuty explains that redwoods are hexaploid, meaning they have six sets of chromosomes, rather than the two sets of chromosomes that humans have.
"Genetically speaking, coastal redwoods are playing with a much bigger
deck of cards than we humans are. There are more genetic combinations
possible," as Amy puts it. Redwoods are thought to be the most adaptable tree on earth by being able to change their genes so readily.
"Every time a sprout comes up with slightly different genes, it's kind
of like an experiment. If it works, that tree might set the course for
the generations of the future.They can develop resistance to fungi. They can develop resistance to viruses. They can develop better growth patterns," Dave explains. But, because these mutations are random, some of the new traits developed are no use at all - positively harmful, in fact.
"Albinos probably aren't a particularly good modification, from the standpoint of the health of the forest, but they demonstrate there's a lot of experimentation going on," Dave says. And in the long term, a few parasitic albino trees are worth it, for all the benefits that this genetic variation can bring.