Species of Salicornia are found all over the world as both annuals (seasonal) and perennials (grow year round). Salicornia europeae var. rubra is an annual that grows in salt watermarshes in the interior states of the United States.
Pickleweed (S. europeae var. rubra) growing around Great Salt Lake is different from the coastal varieties due to its adaptation to this extremely saline (salty) environment. Pickleweed can grow in a soil salinity of up to 6%,but is typically found in salt playa areas with approximately 2.4% salt.
secret to pickleweed’s high salt tolerance is found within its cells.
Salt is a combination of two atoms, chlorine (Cl) and sodium (Na).
It is known as sodium chloride (NaCl). When salt dissolves in water,
the particles, or ions, Na+ and Cl-, are separated from one another
by water particles, much like cream molecules are separated and dispersed
by molecules of a coffee mixture.
When the plant absorbs water through its roots these dissolved particles flow into the plant with the water. Salt in high concentrations is highly toxic to the plant. Therefore, there must be some kind of mechanism that can filter out or excrete the salt from the leaves and remove it from the cells.
Some salt is filtered out at the roots by tiny sodium-potassium pumps within the cell membrane. Although these pumps filter out a lot of the salt there is still a great deal that “leaks” into the plant. Some salt plants, like salt grass have glands which take the excess salt and secrete it out of the cells to the surface of the leaf. However, pickleweed does not have salt secreting glands. Instead it has a special storage facility - the vacuole, a membrane bound structure inside all plant cells. To learn more about the internal structure of plant cells visit the "virtual cell" website.
(Trefil & Hazen, 1995)
In salt-succulent halophytes like iodine bush and pickleweed, energy requiring pumps within each cell move the salt into the vacuole where it is stored. When the vacuole cannot hold any more salt the cell breaks down and dies. Younger cells then take over the job of pumping and storing salt. This process results in what is called "salt-succulence", where the green photosynthetic tissue of the plant has many large cells holding massive amounts of salt in the interior vacuoles of the cells. If you could taste the glands they would be very salty like pickles. That's how they got the name pickleweed.
At the beginning of spring, pickleweed seeds that have been dormant on the soil's surface, or in the mud of the playa throughout the winter, are swept up, dispersed, and deposited by annual floods. Tiny hairs allow seeds to “hitchhike,” trapping air bubbles to float, or attaching to floating debris through the marsh (Ellison, 1987). Once a seed is leached of germination inhibitors and deposited on the surface of the soil it germinates and grows.
The young plant grows slowly throughout the summer, and at the end of the growing season, six flowers bloom from each node of the stem. These flowers are displayed in groups of three; the middleflower producing a large seed and the smaller flowers each producing a smaller seed. The large seeds are the first to germinate in the spring while the more abundant smaller seeds lay dormant for a few months longer, germinating in May or June. Some seeds lie buried in the mud for years before germinating. It is not known how long seeds can lie dormant in the soil.
As the days grow shorter and cooler the plant begins to change to a brilliant red color. Soon, winter freezes the ground and the plant dies, its seeds lying scattered nearby waiting for the spring thaw, the playa pond to form from snow and rainfall, and life to cycle once more. The playa margin where pickleweed can grow changes each year with the winter/spring precipitation controling leaching of seed germination inhibitors along with shoreline dispersal of seeds. The mud flats around Great Salt Lake are determined by the long term rise and fall of Great Salt Lake water levels. The Halophyte Transect Section in the introduction shows where pickleweed can be found in relation to other vegetation types.
Walking through the salty marsh, an observant student notices that pickleweed is found in abundance at the basin at the base of small dunes and elevated areas. As these upland area above the pickle weed flats slightly increase in elevation and the soil salinity decreases, a greater variety and abundance of plants is found. These upland areas are termed salt plains and are typically covered by greasewood, alkali dropseed, or other species of saltbush. Pickleweed, however, is not seen among them. This is probably because pickleweed, with its energy demands for internal salt regulation, cannot compete with the other plants that grow in less salty soil, and have probably evolved germination “cues” that require predictable winter/spring flooding.
When the floods come in they deposit diluted salt water at the base of the elevated areas that have been carved by flood water. When the waters retreat they have dispersed pickleweed seeds at the upper playa margin throughout the area. These seeds then germinate and grow on playa margins just below elevated uplands. Most upland plants cannot grow in the playa basins because the salt concentration after the water evaporates is so high. However, they thrive on elevated areas because salt concentration is lower due to yearly leaching by snow and rain. These plants with deeper roots could grow over the pickleweed blocking sunlight. Without light from the sun, or nutrients from the roots, pickleweed can not grow. So it would die from competition or drought amidst other plants on the uplands.
Pickleweed requires continual ground water throughout the growing season because its root system is so small. It survives and thrives on playa basin margins because there are no other plants to compete with. In certain areas, like the middle of the playa, salt is too concentrated for pickleweed seedlings to germinate and grow or else the playa water was too deep to allow spring time germination.
This complex distribution pattern of pickleweed on the saline playa of Great Salt Lake changes from year to year, depending on the interaction between precipitation, water depth, and salt concentration.
Pickleweed plays many roles within this unique ecosystem. It is food for birds and mammals. The savannah sparrow and other seed-eating birds feed on pickleweed seeds during harsh winter months. Small mammals like the meadow vole may also forage for seeds within the pickleweed zone.
Insects found within the pickleweed zone are eaten by birds such as the snowy plover that nests in the bare playa margins adjacent to Pickleweed. In New England, Salicornia europeae buds are devoured by beetles,and moth larvae feed off seeds (Ellison, 1987).
Most importantly, pickleweed is a "successional" species. It is one of the first to start growing after flooding disturbance, establishing a “pickleweed zone” in the most salty soil. This zone changes each year with Great Salt Lake flooding disturbance causing it to vary in width and size depending on the elevation of Great Salt Lake, or the depth of the various playa ponds.
Pickleweed is truly a fascinating plant.
Ellison, Aaron M. 1987. Effects of Competition, Disturbance, and
Herbivory on Salicornia Europaea. EcologyVol
68 No. 3. pp 576-586.
Utah State University. Department of Geography. <http://www.nr.usu.edu/Geography-department/utgeog/utvatlas.htm>(October 1999).