Plants that aren’t green

finding other sources of metabolites

Most of us think of plants as being green, at least in summer. The green comes from the pigment chlorophyll, which uses sunlight to knit carbon dioxide and water together, forming carbohydrates that the plant can metabolize. Lucky for us, oxygen is a by-product of the process. There are a few local plants, however, that don’t have chlorophyll, or at least very little, so they don’t do photosynthesis and have to obtain their energy elsewhere. Here are examples:

Northern ground cone. This interesting Beringian plant goes by the reverberating scientific name of Boschniakia rossica, named for a Russian botanist Boschniak and presumably someone named Ross. Such names reflect nothing about the plant itself, obviously, and only show who knew whom. That’s a shame, because this plant is rather weird and wonderful.

Northern ground cone got its common name because, to some people, the above-ground plant resembles a pine cone. It is common in certain places around here, mostly where there are alder trees. Lacking chlorophyll, it cannot synthesize carbohydrates for itself. Northern ground cone is entirely parasitic, getting its nutrition from other living plants, especially alders but also other species.

The brownish spike that emerges from the ground in summer is the inflorescence, bearing numerous small flowers. When mature, the spike produces huge numbers of tiny seeds.

The plant is reputed to have some medicinal value for humans (although, like many plant medicines, it has some toxic properties too), but part of my interest in it stems from observing that it seems to be a favored food item for bears. In the Dredge Lake area, for example, I often see wide swaths of ‘rototilling’, showing where bears have been foraging for northern ground cone. Bears seek out the underground base of the spike and generally leave behind the spike itself. The stem-bases are not notably rich in basic nutrients such as nitrogen, phosphorous, potassium, or calcium, and probably provide carbohydrates. When bears have been eating lots of ground cone, their scats look (to me) rather like mushy cracked-wheat porridge.

fly-entering-groundcone-flower-by-bob-armstrong
A fly enters the flower of a northern groundcone. Photo by Bob Armstrong

The tiny flowers are accessible to small insects, which are sometimes seen to visit, but it is apparently not known if they are pollinators. A different species of ground cone is reported to be self-pollinating, and a little fly sometimes attacks the flowers of that species. But the story for northern ground cone is yet to be discovered.

Pinesap. This is another strange plant that lacks chlorophyll. Pinesap (alternatively, Dutchman’s pipe) grows under conifer trees. It seems to be much rarer than ground cone in our area, as I have almost never seen it around here. It is sometimes said to be saprophytic, obtaining nutrients from decaying vegetation, but the reality is more complex. This plant and its close relatives are obligately dependent on mycorrhizal fungi whose underground filaments connect to the roots of nearby trees. The fungi draw nutrients from the host trees and delivery them to the pine sap plants. Thus, the pine saps are indirectly parasitic. Pine saps have yellowish or reddish stems, with yellowish or red-tinged flowers usually bent over to one side. When the fruits mature, however, they are upright on the stem. Bumblebees are reported to be the most important pollinators.

Certain local orchids are also saprophytic. We have two species of coral-root orchids, both of which are said to be saprophytic, but again the arrangement may be more complicated. In addition to needing mycorrhizal fungi for seed germination, these plants may, like the pine sap, actually obtain nutrition via their associated fungi that drain nutrients from nearby host plants. In addition, one coralroot orchid is said to have small amounts of chlorophyll and thus synthesize some of its own carbohydrates. Coralroots may be pollinated by small flies, such as dance flies, but probably also have the capacity for self-pollination.

Ralston Island

observations by amphibious naturalists

We left our camp on Lincoln Island in sunshine, with a following breeze. Arriving quickly at the wide beach on Ralston, we set out to explore the island. The trail marked on old topo maps proved hard to find, but a maze of deer trails made it easy to move around the forest. We wandered toward the north end of the island.

All along the way, I enjoyed the numerous flowering orchids. All had tiny, intricate flowers, rather than the showy ones that most folks notice. There were twayblades, named for the paired leaves on the stem. Darwin, long ago, figured out just how the little twayblade flowers contrive to be pollinated by visiting insects: when an insect touches a certain part of the flower, a sticky drop explodes outward, carrying pollen and sticking it to the insect, which carries it to another flower.

The most common orchid was one known as one-leaved malaxis or white adder’s tongue. A single leaf sits at the base of the flowering stem. There are no adders involved here except in somebody’s over-active imagination! We also noticed several rattlesnake plantains, which are not plantains at all. Nor do they have anything to do with rattlers, except that someone decided that the patterns on the leaves looked like snakeskin.

The most colorful ones were the pink coralroot orchids, which lack green pigment and so cannot synthesize their own carbohydrates. They are variously reported to be saprophytic (feeding on decaying organic material) or indirectly parasitic on other living plants by means of fungal connections. Ralston hosted some spectacular stands of this orchid.

As we strolled around, we saw no signs of red squirrels or porcupines, which presumably would have a hard time getting out there. Juvenile ravens were loudly making known their wants, as they tried to follow their harried parents through the trees. Songbirds still sang, even in late June; I heard song sparrow, hermit thrush, ruby-crowned kinglet; one hermit scolded us severely, using notes I’d not heard before, so we must have been too close to a nest or chick. A strange-looking woodpecker moved through the canopy; after checking the books, I guessed it was a hairy woodpecker—which are darker here on the coast than they are elsewhere.

The north end of the island was productive. There’s the densest, tallest stand of crabapples I’ve ever seen, and some of the gnarliest hemlocks. As we pushed through the brush toward a boulder shore, we stumbled into a small meadow, perched on a headland and sporting a surprising and lovely stand of wild iris. Out among the boulders we finally spotted some oystercatchers displaying to each other, apparently amicably. Later, we saw an oystercatcher vigorously and loudly chasing an eagle, which presumably had had designs on an oystercatcher chick.

Then it was time to head back to camp. Ah, but by now the tide had turned, not in our favor, and the headwind had risen noticeably. It seemed do-able, however, so off we went. Around the first point, things became more difficult: a stiffer breeze, a stronger tidal current, and there were also frequent, strong gusts of wind. We had to paddle hard and constantly, just to keep from going backward! In between those gusts, slow forward progress was possible, but it still took about four hours of nonstop hard paddling to get back to camp. Ooooofff!

Parasitic flowering plants

trouble underground

When we think of parasites, we usually think of tapeworms, ticks, fungi, and assorted micro-organisms. But the world of flowering plants provides some interesting examples of a botanical version of parasitism, in which one plant extracts nutrients from another. We have two quite conspicuous and common kinds of flowering-plant parasites: hemlock dwarf mistletoe (Arceuthobium campylopodium) and northern ground cone (with the resounding name of Boschniakia rossica). Both of these species are entirely parasitic (or almost so). They derive all or almost all of their nutrients from their host plants and are unable to survive without a host.

You may have noticed the ‘witches brooms’ of gnarly, tangled branches that are the result of a mistletoe infection. The mistletoe alters the balance of growth hormones in hemlocks (and sometimes other species), causing the ‘brooms’. Male and female mistletoe plants are separate, with very small, inconspicuous flowers. Pollination is mostly by wind. When the seeds mature, they are discharged explosively; they are capable of travelling ten yards or more. Because they are sticky, they adhere to other branches or trunks and start new infections. This species has been reasonably well studied, because heavy infestations decrease the economic value of the timber.

 

The ground cone pokes up above ground in June. All we see is the cone-like inflorescence of tightly packed, brownish flowers; the rest of the plant is underground. Ground cone is commonly parasitic on the roots of alders, and sometimes other species, including blueberries. Various insects may visit the flowers and accomplish pollination; occasionally we have seen bumblebees probing the flowers. The seeds are minute and very numerous. The biology of this species apparently has not been studied in detail, as I can find no scientific papers on the subject, but the medicinal uses of this plant are reported to be many. We do know, from local observations, that bears frequently dig up and eat the underground base of the flowering stalk.

In addition, all orchids depend on their mycorrhizae (fungal associates) at least at some time in their life history. Some researchers consider the relationship to be mutualistic, with both participants gaining some advantages, and that eventually may be the case when the adult orchid develops green leaves and can provide carbohydrates to the fungus in return for soil nutrients. However, other researchers refer to mycorrhizal associations as a parasitism by the orchids on the fungi. This seems especially applicable in the case of orchids that develop little or no green tissue as they mature, so they can contribute nothing to their fungal associates. We have two species of the genus Corallorhiza (coralroot), one of which has no green tissue at all, while the other has a little and so can make some carbohydrates. They are both parasitic on fungi for all of their lifespans, but the relationships are even more complex: they can indirectly parasitize green plants through their fungi, which attach to the roots of trees and shrubs (which have their own mycorrhizae), and draw nutrients from those hosts.

Less well known are the so-called hemi-parasites, half parasitic and half independent. They have chlorophyll and can synthesize carbohydrates, but also commonly latch on to other plants and capture some nutrients from these hosts. We have a number of hemi-parasites among our local flowers.

The plant called yellow rattle or rattle box (Rhinanthus minor) grows in open areas at low elevations. This species is capable of parasitizing the roots of many other herbaceous species, including grasses. A single Rhinanthus plant can attach itself to the roots of several other plants. Some plants, however, are able to resist invasion by the roots of the parasite. Rhinanthus plants clearly benefit from the parasitic connections, growing and reproducing better if they are connected to a host. Some hosts, such as legumes, are better than others in providing the parasite with nutrients. In addition, the parasite can take up defensive chemicals, such as alkaloids, from the host, and thus reduce the risk of herbivory. The effects on the host plants are negative, because many of their nutrients are drained away by the parasite; parasitized hosts have decreased growth and reproduction; the negative impact is greater in some hosts than in others. There are indirect effects of Rhinanthus parasitism too: parasitized hosts have lower ability to compete with other plants in the community, and lower ability to recover from herbivory, which then affects the relative abundance of various species in the entire community.

Pink-Indian-Paintbrush-1
Photo by Bob Armstrong

There are three species of Indian paintbrush (Castilleja) in Southeast, but only one has been studied much, and those studies were conducted elsewhere. In general, members of this genus grow better, flower more, and resist herbivory better, when they are connected to a host plant. Legumes seem to be better hosts than other plants, and two or more hosts may be better than one. When a parasitic paintbrush plant dies and decays, decomposition is accelerated, and co-occurring species have increased productivity, which may counter the usual negative effects of the parasite to some degree.

The genus Pedicularis—the louseworts–has about five representatives in our area, which have not been studied directly, as far as I can tell. In general, the negative effects of parasitism by different species of lousewort may vary among host species, and different louseworts have different host preferences. Some louseworts are reported to have mycorrhizal associations too, collecting nutrients via the fungal connection in addition to the usual direct parasitism.

Clearly, the world of the parasitic flowering plants is complicated, and it gets more complex as more studies are conducted. All those pretty (and not so pretty) flowers are intricately involved with many ecological interactions, and what we see above-ground is only a small part of the story.

Orchid variations

the complex lives of some fascinating flowers

Southeast Alaska has several species of orchid, which are not as gaudily showy as the types cultivated by orchid fanciers, but they have their own allure. Many local folks are familiar with the white bog orchid, whose tall inflorescences send out such a lovely aroma. This species is probably pollinated by moths that come to collect nectar. The calypso or fairy slipper orchid draws in bumblebee pollinators by looking lovely and smelling sweet, as if it offers nectar, but it has none. Visiting bees learn quickly that these flowers offer no food reward, so successful pollination depends on a supply of inexperienced bees. (Calypsos, and perhaps other orchids, should not be picked, because that tweaks the delicate root system and is likely to kill the plant.)

fairyslipper-orchids-by-bob-armstrong
Calypso orchid. Photo by Bob Armstrong

In addition to a wide variety of relationships with pollinators, orchids and many other flowering plants have an intimate relationship with fungi that connect with their roots. This mycorrhizal (fungus-root) relationship is classically thought to be mutualistic: both partners get something from it. The fungus gets carbohydrates from the plant, which typically has chlorophyll (green pigment) and synthesizes sugars that the fungus cannot make for itself. The flowering plant gets nutrients that the fungus gleans from the soil or decaying organic material. Some researchers suggest that mycorrhizal associations were probably essential when plants began to colonize land, millions of years ago.

Orchids, however, take mycorrhizal relationships to new levels of complexity. All orchids produce minute, dust-like seeds. The seeds are so tiny that they contain almost no stored carbohydrates or other nutrients that are needed for germination and growth. They rely on mycorrhizal associations to provide the nutrition needed for germination and initial growth. Thus, all orchids begin their lives as parasites, not mutualists, of fungi (the fungus gets nothing from the seed).

Now the fun begins! Some orchids have no green pigment, so they can’t photosynthesize carbohydrates to give to the fungus. These species remain parasitic on their fungi throughout their lives. The fungus may extract nutrients from the soil and decaying vegetation. However, in many cases, the root-associated fungus acts as a conduit for carbohydrates and other nutrients from a tree (which does have green pigment and can synthesize carbohydrates). So the orchid then is also indirectly parasitic on the tree to which it is connected. For example, in the yellow coralroot orchid (Corallorhiza trifida), which grows here, the fungal associate connects the roots of several species of tree to the orchid, and the orchid thus pirates nutrients from the trees. Even orchids with green pigment and photosynthetic ability may extract carbohydrates from the associated fungus (and a connected tree) without giving anything back, so they, too, are at least semi-parasitic, in many circumstances.

In a further evolutionary complexity, many orchids ‘eat’ their fungal associates, digesting the ends of fungal filaments that connect to the orchid. If the orchid does no photosynthesis, it thus seems to be destroying at least part of its essential source of nutrition. Even if the orchid can photosynthesize carbohydrates, digestion of filaments would interrupt the derivation of materials by the orchid from the fungus or a connected tree, at least partially.

The digestion of fungal filaments opens up many questions, to which I’ve found no concrete answers in the literature (although this fact has been known for over a hundred years): Why would the orchid destroy a major source of nutrients? Is it not needed any more? Or are only certain filaments eaten? What is the contribution of the digested filament itself to orchid nutrition, compared to what the filament delivers from a tree? What is the effect of filament digestion on the fungal organism? Does destruction of the orchid-connected filament tips affect the growth and reproduction of the fungus, as well as limiting its expansion in the orchid roots?

Whether parasite or mutualist, some orchids keep their mycorrhizal associations all their lives, some change their fungal associates as they grow, and some apparently become independent of fungi as they mature (especially if they grow in rich soil with good sunlight).

Things get still more complex: Within some orchid species, genetically different individuals have their own, specific mycorrhizal associates. For example, different genetic types of the spotted coralroot (Corallorhiza maculata), another local species, are reported to have different mycorrhizal associates, accompanied by subtle differences in floral shape. A given population of this coralroot orchid may contain several genetic types (or races) of the orchid, each with its own floral features and fungal associate, potentially deriving nutrients from a variety of trees.

Worldwide, the orchid family encompasses many thousands of species, hugely diverse in floral structure, as well as habitat, leaf shape, life history, and so on. The traditional explanation for the great diversity is adaptation to an equivalent diversity of pollinators. For instance, both of our local species of coralroot orchids are pollinated by small insects such as dance flies, in contrast to the bee-pollinated calypsos and the moth-pollinated bog orchids. However, it has recently been suggested that some of the great diversification of orchids may be related to adaptations to different fungal partners. The variety of floral design and fungal association within the single species of spotted coralroot suggests that this may be a step toward the origin of several new species.

An extended day…

expected and unexpected discoveries

When the day began, we only intended to stroll to Outer Point on Douglas in search of the spotted coralroot orchid. Rubber boots were needed for crossing Peterson Creek, but by the end of the day, I was wishing I had a change of footgear. Searching through the understory for some time, we finally noted some small spikes sticking up out of a old rotten log–a limited success, because they were not yet blooming. We’ll have to wait a week or two to get a good picture of the pinkish flowers.

Because the tide was low, we then ambled out along the long storm berm to Shaman Island. Dodging the war games of some rambunctious kids, I learned where to look or some super-sized barnacles down near the low tide line. I’d like to know more about these—are they a different species from the usually types that cluster all over the stones and mussel shells, or are they just unusually happy? (In Chile, where I spent many months in the austral springs, the giant barnacles are considered to be a delicacy!)

rbsapsucker-armstrong
Photo by Bob Armstrong

By now, it was well past noon and both of us felt hungry and a little frail. But we decided to go up the Eaglecrest road to check on a willow tree that has been much used by sapsuckers, which drill sap wells in the bark and lap up the sap and any stuck insects. We found the tree, and a sapsucker arrived while we watched, so all the recent construction at this spot hadn’t destroyed the bird’s favorite lunch stop.

Best of all, a group of Plein Rain artists were gathered nearby, enjoying a chilly workshop with a visiting artist—and they had food! By managing to appear really wan and wobbly, we persuaded these very kind folks to feed us too! Many thanks to these good Samaritans! And the art work spread out along the walkway was very nice too—Juneau talent at work!

Reinforced by serendipitous sustenance, we decided to check out a bird nest down along Fish Creek. A short walk by the stream and a brief sit-down on the bank let us get a good look at the nest. At this point the sit-down was welcome, because my feet do not like walking or standing around in rubber boots.

Returning to the car over the new footbridge over Fish Creek, we hailed two other friends, also out for a walk. They had recently seen a female common merganser with eight chicks on one of the nearby ponds, and some of the little ones were riding on mama’s back. We inspected a beaver lodge and some recent beaver cuttings, and enjoyed a long chat.

Thus the day turned out to be much longer and far more social than initially planned. But that is not a complaint (even though my feet said otherwise…)!

 

The next day, three friends hitch-hiked a ride out to Portland Island. The crabapple trees were blooming, although they looked decidedly weather-beaten. The oystercatchers and Arctic terns had eggs and were incubating. Their nests in the sands of the upper beach are nothing more than a saucer-shaped depression, very difficult to spot and easy to crush accidentally, so it is not a good place to walk. One oystercatcher was implanted with a tracking device a few years ago, in order to learn a bit about migration patterns, but she is back again, nesting in almost the same location as in previous years, and incubating three eggs. For some reason, the wire antenna extended from her backside does not seem to interfere with mating or anything else. We got too close to her nest, and she put on a great broken-wing act, with much shrieking in protest. We left in a hurry!

The density of song sparrows was notably high. Some were feeding fledglings, which shrilled their begging calls from deep in the dense vegetation, and others were still feeding nestlings. Because they were still singing frequently, I suspect that they intended to start second broods.

A gang of gulls loafed around on a sandbar. They seemed very nervous, lifting off en masse every few minutes. Some of these flights were probably in fear of an eagle flying by, even if the eagle was far away and seemingly intent on something in the distance. Perhaps the gulls know from experience that eagles can look deceptively innocent but quickly become malevolent.