Along the banks of some parts of the North Fork Tuolumne River, you'll see collections of bright pink strands in the water. Some are dense, fibrous mats, while others are slender, worm-like appendages. Where do they come from? What do they do? And why are they so vividly pink?
We're not entirely sure ourselves, as there's little literature to tell us. However, over the course of our trip down the river, we developed some good theories.
Patrick: Our botanist friend Nick said they were alder roots... my first impression was that they were reddish because they were used for photosynthesis.
Anna: This made sense to me... if blue light penetrates water while red is the first one absorbed, then they'd be red to take advantage of the blue light, like red algae in the ocean.
P: Yeah, and since the roots are in water, the red that is normally absorbed by green leaves in the air doesn't make it to the roots.
A: Also, we noticed that the red pigmentation seemed to only exist on the portion of the roots extending into the water column, while the roots embedded in the soil were still white.
P: Well, that's because they wouldn't be photosynthetic if they're buried in the soil.
A: We thought we were on to something....
P: But what if it's more like a protective mechanism instead of a photosynthetic thing, because they're exposed?
A: Hmmm... UV light can be damaging, and if these roots were exposed to UV radiation it might be beneficial for them to develop pigmentation to shield them from harm.
P: But wouldn't it take more work to produce this shielding? If these plants are growing roots in the soil anyway, why would they extend them into the water, where they have to protect them?
A: Yeah... good point. And we still haven't discovered where they are coming from...
P: Nick said they were alder roots, but the bushy fibrous ones we saw on NF's river left were nowhere near any alders. Maybe he doesn't know his ash from his elbow-bush? (Sorry, Nick!) It seemed like all those pink mats were near willows, and not alders... could they be something else?
A: Like what? Not roots?
P: Yeah, like a parasitic epiphyte, which is just another plant attached to the stems and roots of other plants like an obnoxious pink hair extension... remember when we saw that one growing out of the side of the submerged willow stem up at Clayey?
A: Right. It did look different than the other, lower roots when we pulled the baby tree from its rocky crevice (oops! Sorry!). But adventitious roots sometimes look like that - perhaps they grew later than the others, after a portion of the trunk had become inundated.
P: Ohhh right.. and they will often extend into the water at or near the surface to take advantage of the nutrients in the water itself, especially if the underground roots are in a low-oxygen environment.
A: So what else could they be? So far we only have proof that they are connected to willows...And are they only willow roots? That was when we stumbled upon the worm-like appendages. And interestingly enough, they were coming straight out of the base of an alder. So Nick was right, alders make pink roots too.
P: Yeah, that's right. Our friend Carson also confirmed our suspicion that they were roots when he told us that he saw the bushy-type ones coming out of willows a lot, down at Consumnes. So the bushy ones are adventitious willow roots, and the wormier ones are from alders... but we still haven't figured out why they're pink...
The question mulled around in our brains, and when we got back to our beloved Internet after the trip, we did a little research.
Patrick: Hey! It turns out that there's a plant, Petrorhagia velutina, called the Hairy Pink! (p.s. be careful what you Google...)
Anna: True. But that discovery is totally unrelated to the mystery of the willow and alder roots. We also discovered that there is a protein called leghemoglobin associated with nitrogen-fixing nodules on aquatic roots. And yes, it is related to hemoglobin, which is tinted red...
P: Yeah, hemoglobin makes our blood red, and it turns that color when it's saturated with oxygen. So why is it in nitrogen-fixing nodules?
A: The plants have a symbiotic relationship with bacteria living within those nodules, and those bacteria use an enzyme called nitrogenase to convert nitrogen in the water to the kind that plants can use. Apparently, nitrogenase works best under low oxygen conditions. By producing leghemoglobin in the root nodules where symbiotic bacteria live, the riparian trees are able to bind oxygen molecules, and create the low oxygen environment ideal for their symbiotic buddies.
P: So in mutualistic symbiosis, the bacteria get a place to live and work, and the plants get nitrogen from the water that they otherwise couldn't... but from everything I've been able to find, that should only be happening in little nodules, not over the entire root. Looking under a magnifying glass, I can see that the willow roots are actually covered in little pink dots. But that doesn't explain why the entire alder root is a vivid red...
A: Right...and this is where it becomes evident that neither of us have all the answers. Perhaps we will have to leave this mystery up to someone else to solve. Are the roots red because they are photosynthesizing? Because they are trying to protect themselves from UV rays? Does the color result from a symbiotic relationship? Is it a combination of these factors, or something else entirely? Regardless, it is a pretty awesome to see the thick pink masses waving underwater all along the banks of the lower North Fork of the Tuolumne.
P: The Cyndi Lauper of the Tuolumne watershed....
Resources:
‐
Sadava,
DE,
et
al.
Life.
Gordonsville,
VA
:
W. H.
Freeman
and
Co.,
2008.
789.
‐
Tiner,
RW.
Wetland
Indicators:
A
guide
to
wetland
identification,
delineation,
classification,
and
mapping.
Boca
Raton,
FL:
CRC
Press
LCC,
1999.
60.
Special thanks to Nick Jensen and Carson Jeffres
Photos:
Side‐by‐side:
Patrick
Hilton
North
Fork:
Nick
Buckmaster
Cyndi
Lauper:
http://suicideblonde.tumblr.com/post/122457578/cyndi‐lauper