Eriocaulon decangulare, E. compressum
John and George enjoyed getting out into the piney forest today; after a chilly dawn the day turned spectacular. We planned a group walk through a scrubby pinewoods zone in Seabranch State Park. Most of today’s sightings have already entered this blog, so we’ll drift to the marshy area near the swamp where we’ve spent much time lately. (OK, we got lost there.) (Really)
As an aside due to John getting us into ants, in every sense, here is some ant biz. In marshy places (this photo from the Cypress Creek Natural Area) are ants in big papery nests resembling hornet nests, and presumably safe above the high water line. They seem to be Crematogaster atkinsoni, known to behave this way in Florida. But don’t bet the (ant) farm! This is a plants blog.
Attractive in the midwinter sunshine are species of Eriocaulon and similar genera in the Pipewort Family. They go by several English names: Hat Pins, Pipeworts, Bog Buttons. Some folks hitch the different English names to individual genera, but the species all look too much alike for single handles to stick to single species. The flower stalks truly do look like hat pins, the plants standing from a few inches tall to knee-high depending on the age, habitat, and species.
Now consider briefly a separate group of aquatic plants, the genus Isoetes, also known as quillworts. There are plenty in Florida but not in our immediate haunts. The reason for an intrusive Isoetes non sequitur is to explain the name “isoetids,” defined as plants resembling Isoetes not as genetic relatives, but as unrelated species sharing a peculiar aquatic growth form. They look like slightly succulent grasses. The plants have air channels in their leaves and roots, and have roots clustered intimately with the leaf bases. The root mass is disproportionately large relative to the foliage.
The isoetids have a unique life style to go with their characteristic life form. The most abundant and thoroughly studied example in our area is the so-called Ten-Angled Pipewort, Eriocaulon decangulare. The similar Eriocaulon compressum has the same structure.
If you’ve read through the boring blah blah blah this far perhaps you’re waiting to see the shockingly unique life style unveiled. Here we go: In second grade we all learned that plants absorb carbon dioxide through their foliage to let photosynthesis manufacture sugars. But today we learn that is not the whole truth and nothing but the truth.
When you spy a plant with big puffy air channels in its leaves and roots, it is natural to assume a ductwork system open to the clear blue sky. Those roots need help down in the mud! But no—wrong, or partly wrong. Here’s the problem. Many isoetids live completely submerged with no opening to the air. Ooops, we have the airshaft upside down—-they are exchanging gases through the roots.
A completely or partially submerged plant lives in stinky goo with plenty of decay going on down there. The roots absorb carbon dioxide from soil microbial activity, bacterial waste gas, sending the CO2 upward to the leaves for photosynthesis. And waste oxygen escapes down and out through the roots.
This creates the possibility of symbiotic relationships with soil bacteria happy to “breathe” that waste oxygen exiting the roots, and eager to make carbon dioxide to enter the roots. Maybe those bacteria are even decaying material the plant produces. I’ll bet that’s happening with Eriocaulon, but am not aware of research showing it in that genus. Gas-exchange symbiosis with root bacteria is, however, documented in Isoetes itself. Just think, the entire cycle of life, a mini ecosystem, all in one cubic foot of soil. Maybe.
Note. For a deeper look: Raven, J. A. et al. The role of CO2 uptake and CAM in acquisition of inorganic C by plants of the isoetid life-form: a review, with new data on Eriocaulon decangulare L. New Phytologist 108: 125-148. 1988.