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In biology, it is often the exceptions to the rules we teach that are the most interesting organisms. For example, every child knows that the sky is blue and the grass is green. With a few leading questions you can get a child to generalize that all plants are green. We all know this, right? Plants are green because they have chlorophyll, which allows them to perform the magic of photosynthesis. And yes, it really is magic. Harvesting the power of the sun to build complex molecules out of CO2 and H2O? Yeah, photoautotrophs are freakin' amazing.

But what about the plants that aren't green? How do they make a living?

I've already written about dodder, a parasitic plant that is commonly seen growing on pickleweed at Elkhorn Slough. A few weeks ago when I was at Lake Tahoe I encountered another plant that has a parasitic lifestyle: snow plant.

Snow plant (Sarcodes sanguinea) near Carson Pass in the Sierra Nevada
26 July 2017
© Alex Johnson

Snow plant (Sarcodes sanguinea) is a non-photosynthetic plant that has zero chlorophyll and thus zero green color, and is instead a rich blood-red color hinted at by its species epithet. It lives on the forest floor in close proximity to coniferous trees. The blood-red inflorescences shoot up from the ground, apparently out of nothing; the rest of the plant lives underground. If you break an angiosperm into its basic anatomical components you have: leaves, stems, roots, and flowers. Snow plant isn't photosynthetic, so it doesn't need or have leaves. And since stems are essentially support structures to hold leaves up to the light it doesn't have those, either. The roots and vegetative parts (rhizomes?) of snow plant are underground and for most of the year there's no indication that it's there at all, until it sends up an inflorescence in the late spring as the winter snow is melting.

Snow plant (Sarcodes sanguinea) near Carson Pass in the Sierra Nevada
26 July 2017
© Alex Johnson

Since snow plant isn't autotrophic and doesn't fix its own carbon, it has to obtain fixed carbon from elsewhere. Snow plant lives under conifers, but is not a parasite on the trees the way that dodder is a parasite on pickleweed. The relationship is much more complex and involves a third player. And all of the action happens underground.

Enter the third player, a mycorrhizal fungus. This fungus's mycelium spreads through the roots of the conifers with which it has a mutualistic relationship. The tree shares photosynthate (i.e., fixed carbon) to the fungus, which in turn provides minerals to and enhances water uptake for the tree. These mycorrhizal symbioses are very common in Nature, but most often go unnoticed because they occur in the soil.

Snow plant (Sarcodes sanguinea) near Carson Pass in the Sierra Nevada
26 July 2017
© Alex Johnson

Sarcodes sanguinea, the third partner in this unusual plant-plant-fungus ménage à trois, takes advantage of the intimacy between the conifer and the fungus. Instead of parasitizing the tree it targets the fungus, siphoning off part of the fungus's share of photosynthate. I suppose this makes snow plant an indirect parasite of the tree. The tree is doing all the work, as it is the only autotrophic member of the trio. It shares photosynthate with the fungus and gets something vital in return. Snow plant, on the other hand, doesn't contribute anything to either the fungus or the tree. Rather, it takes directly from the fungus and only secondarily from the tree.

It would be interesting to investigate the energetics of this three-way relationship. How do the fungus and tree react to parasitism by snow plant? On which of the mycorrhizal partners does snow plant have the strongest effect? The fungus, because its share of fixed carbon is being drained directly? Or the tree, which suffers because feeding the snow plant via the fungal intermediary means less photosynthate available to support its own metabolic activities? Does the tree have any way to stop the flow of fixed carbon to an area of the fungal mycelium that is being parasitized by the snow plant?

One last note. Many of the snow plants that we saw on the trail out of Carson Pass to Big Meadow had been surrounded by stones. We never saw any signs so aren't sure why, but I think hikers want to keep the snow plants from getting trampled. The species isn't endangered or threatened, although it is restricted to higher altitudes in California's mountain ranges.

Distribution of Sarcodes sanguinea in California

I think the stone rings were put there both to point out and protect the S. sanguinea inflorescences, although it would be hard to miss them. Nothing else is that bloody shade of red, and it really does stand out. Even small plants are very conspicuous.

Small snow plant (Sarcodes sanguinea)
26 July 2016
© Allison J. Gong

What a bizarre plant. It challenges our preconceived notions of what plants are all about. Ain't Nature grand, and weird?

The Sierra snowpack is California's largest single reservoir of fresh water, accounting for 1/3 of the state's water supply1. A state with a mediterranean climate, such as California, receives precipitation only during the short rain/snow season. During years of drought, when the average Californian frets about how little rain is falling, state water managers are keeping a worried eye on the amount of snow falling in the Sierra. Snow surveyors use remote sensing and field measurements to estimate the water content of the snowpack. The snow water equivalent on 1 April is used to compare snowpack water content across years.

The 2016-2017 snow year was a productive one, dumping near-record amounts of 'Sierra cement' on the mountains. (Skiers accustomed to the powder snows of Utah and Colorado often disparage the heavy snow in the Sierra, but Sierra cement carries a lot more water than powder so is much more beneficial to the state's water supply). Most of that snow eventually melts, births streams and rivers, and flows from the mountains to lower elevations. After a good snow year, though, snow fields remain at high altitudes even during high summer. That definitely is the case around Lake Tahoe.

A few days ago my husband and I hiked from Carson Pass to Big Meadow, a through hike about 8 miles long. The hike goes through some gorgeous alpine meadow, with an absolutely stunning display of wildflowers. Even in late July we had to cross several streams and saw lots of snow.

Round Top Mountain, viewed from meadow above Carson Pass
25 July 2017
© Allison J. Gong
Snow field in the high Sierra
25 July 2017
© Allison J. Gong

If you look closely at the bottom photo, you may notice some faint pink streaks on the face of the snow field. This pink snow is called 'watermelon snow' because of the color. It is a phenomenon that occurs only at high altitudes or polar regions in the summer. Here's a closer look, taken with a 70-200 mm lens that I rented for the week.

Watermelon snow
25 July 2017
© Allison J. Gong

Given the color of those streaks, you'd think the organism producing it would be a red alga of some sort, wouldn't you? I did, too, until I did some research and learned that it is a green alga! Chlamydomonas is a genus of unicellular green algae, most of which are indeed green in color because the only photosynthetic pigments they contain are chlorophylls. However, Chlamydomonas nivalis also contains reddish carotenoid pigments that serve to shield the cell's photosynthetic pigments from excess radiation, which is intense at the high altitudes where the algae live. The pigments absorb heat, which increases the melting of snow in the immediate vicinity and provides liquid water that the algae require. Watermelon snow is found in alpine regions across the globe, although it isn't known whether or not the same species of alga is responsible in all cases.

Cross-country skiers and snowshoers pass through these areas in the winter, and never report seeing watermelon snow. What happens to the cells in the winter? Do they die?

It turns out that the alga persists year-round, although in different life history stages. Given the inhospitality of their habitat, most of the life cycle involves waiting in a dormant stage, with a short burst of activity in the spring. The red form that we see in the summer is a dormant resting stage, having lost the pair of flagella possessed by swimming unicellular green algae. These spores, former zygotes resulting from fertilization, are non-motile and cannot escape to deeper snow to avoid UV radiation, so they use carotenoids to serve as sunscreens. They are not dead, though, and continue to photosynthesize all summer. They rest through the winter and germinate in the spring, stimulated into activity by increased light and nutrients, and flowing water. Germination involves the release of biflagellated cells that swim to the surface of the snow, where at least some of them function as gametes. Fertilization occurs, with the resulting zygotes soon after forming the resting spores that result in watermelon snow.

It may seem strange that this organism spends most of its time in a dormant stage, but this is not at all uncommon for things that live in hostile habitats. When conditions for life are difficult, the best strategy can be to hang out and wait until things get better. Chlamydomonas nivalis does this on a yearly basis, as do many of the marine unicellular algae. And some animals, namely tardigrades, can dry out and live for decades or perhaps even centuries in a state of suspended animation, returning to life when returned to water. As with many natural phenomena, this kind of lifestyle seems bizarre to us because it is so unlike how we do things. But if C. nivalis could observe and think about how we live, it would no doubt consider us inconceivably wasteful, expending enormous amounts of energy to remain active at times when, clearly, it would much more sensible (from C. nivalis's point of view) to sleep until better conditions return.

 


1 California Department of Water Resources

For the past several years now I've been using various iterations of an Olympus point-and-shoot camera, mostly for field and lab work. My current version, which I've had for over a year now, is the TG-4, in which the 'T' stands for Tough. This camera really stands up to its name. I routinely clamber over slippery rocks in the intertidal with the camera dangling from my wrist, and it is pretty banged up already. Not a problem! It is also completely waterproof so in addition to knowing that it will take fantastic photos underwater, I don't have to dry my hands before using it! Plus, it fits easily into a side pocket of my daypack for hiking, although I usually just leave it looped around my wrist. This little camera also has a microscope setting that takes great macro shots, which I love. The one thing it doesn't do very well is line up with either of my real microscopes, but I have a gadget that aligns the camera on my phone with the microscope objective lenses so even that contingency is covered.

Lately I've been thinking that it's time to graduate up to a real grown-up camera, one that has interchangeable lenses for more versatility. I particularly want a camera that will take photos of the birds and other wildlife that my TG-4 doesn't allow me to get close enough for, as well as one for general use, travel, etc. I asked my Facebook friends for DSLR recommendations and the consensus is that Canon and Nikon have the best selection for photo quality, build quality, and lens options. I started digging through online reviews and quickly became overwhelmed with technical specs and jargon. Given that image quality is comparable for cameras in the same price range I decided that the most useful bits of information are (1) whether or not I can figure out how to make the dang thing do what I want it to do; and (2) will I want to carry it around so I can use it.

In early August I was up at Lake Tahoe for an extended weekend with family. A friend had suggested renting a camera at lensrentals.com, which was a great idea. I rented a Nikon D7200, the new addition to their advanced hobbyist line, and an 18-140mm lens for the weekend. I took a lot of pictures, trying the camera in different outdoor lighting conditions. I gotta say, the images coming out of this camera are really nice. I didn't alter anything about them, except to decrease the overall file size so the photos load more quickly.

First test: Photos of outdoor scenery. The atmosphere was hazy due to smoke from various wildfires in the greater area, so I had to go up to Carson Pass to get some blue sky.

View from area near Carson Pass. 6 August 2016 © Allison J. Gong
View from area near Carson Pass.
6 August 2016
© Allison J. Gong
Red Lake, near Carson Summit. 6 August 2016 © Allison J. Gong
Red Lake, near Carson Pass.
6 August 2016
© Allison J. Gong
Tree with scars from chains used to pull wagons up the slope, at Red Lake near Carson Pass. 6 August 2016 © Allison J. Gong
Tree with scars from chains used to pull wagons up the slope, at Red Lake near Carson Pass.
6 August 2016
© Allison J. Gong
6 August 2016 © Allison J. Gong
6 August 2016
© Allison J. Gong
Pile of rocks near Carson Pass. 6 August 2016 © Allison J. Gong
Pile of rocks near Carson Pass.
6 August 2016
© Allison J. Gong
6 August 2016 © Allison J. Gong
6 August 2016
© Allison J. Gong
Meadow at Taylor Creek. 7 August 2016 © Allison J. Gong
Meadow at Taylor Creek.
7 August 2016
© Allison J. Gong
Aspen trees at Taylor Creek. 7 August 2016 © Allison J. Gong
Aspen trees at Taylor Creek.
7 August 2016
© Allison J. Gong
Mt. Tallac 7 August 2016 © Allison J. Gong
Mt. Tallac
7 August 2016
© Allison J. Gong
Taylor Creek 7 August 2016 © Allison J. Gong
Taylor Creek
7 August 2016
© Allison J. Gong
Taylor Creek 7 August 2016 © Allison J. Gong
Taylor Creek
7 August 2016
© Allison J. Gong

Second test: Macro. I borrowed a macro lens from a friend who owns the Nikon D7100, just to fool around and see what happens. I took some macro shots of tree bark. Of course, any time you shoot macro you lose depth of field, which can look sort of cool in itself.

DSC_1057 DSC_1054

Test 3: Wildlife photography. I learned that for wildlife photography, the quality of the camera and lens has a HUGE effect on how the pictures look. I found that this Nikon was pretty responsive, which is important when the subject of the photo is active.

I have no idea if these rodents are squirrels or chipmunks.

DSC_1208 DSC_1202

At Taylor Creek I took pictures of birds!

Steller's jay (Cyanocitta stelleri) at Taylor Creek. 8 August 2016 © Allison J. Gong
Steller's jay (Cyanocitta stelleri) at Taylor Creek.
8 August 2016
© Allison J. Gong

And using the digital zoom that the image quality allows, I get this:

Steller's jay (Cyanocitta stelleri) at Taylor Creek. 8 August 2016 © Allison J. Gong
Steller's jay (Cyanocitta stelleri) at Taylor Creek.
8 August 2016
© Allison J. Gong
Black phoebe (Sayornis nigricans) at Taylor Creek. 8 August 2016 © Allison J. Gong
Black phoebe (Sayornis nigricans) at Taylor Creek.
8 August 2016
© Allison J. Gong

But the best wildlife photo was taken at nightfall. We had gone out to Taylor Creek one evening to look for birds. It was almost full dark and we were about to leave when we saw a large grayish blob in a tree. Looking through binoculars we could see that it was clearly a creature of some kind, but we couldn't tell what. A large owl, getting ready to go out hunting? A roosting raptor?

Surprise! It was a mother porcupine nursing a baby.

Common porcupine (Erethizon dorsatum) nursing her baby in a tree at Taylor Creek. 7 August 2016 © Allison J. Gong
Common porcupine (Erethizon dorsatum) nursing her baby in a tree at Taylor Creek.
7 August 2016
© Allison J. Gong

This photo was the most impressive shot I got from this camera. Its performance in low light conditions was phenomenal. It was almost completely dark when I took this shot, but the exposure looks like it was taken during the day. Color me very impressed!

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