Newsworthy

On an irregular basis, a new ‘feature’, called Marsh Meanderings, will appear.

This second is about Jewelweed.  Do check the calendar for field trips and other  programs.

Marsh Meanderings II.
Jewelweed (Impatiens capensis Meerb.)

22 August 2019

Jewelweed, a common Abbott Marshlands plant, is found in marsh and swamp as well as moist upland locations. In the tidal marsh it can reach 6 feet in length; in other places it may be only a few inches tall when it flowers. In late summer into September in moist areas, its orange flowers with red spots can be conspicuous. Look for them along stream and pond edges and wet road sides. Plants are killed by frost.

This is a species with many names, each tells a little about it:

 

Names
Common names:
Jewelweed & Silverleaf – leaves held under water appear silver because of a thin film of air trapped on the surface by microscopic hairs. Leaves are not wetable; water beads on surfaces as if they’re covered with oil. This is especially obvious on the undersides of leaves. The adaptive value of this waterproofing is not known.

Touch-me-not & Snapweed -refers to the explosive ripe fruits. Ask an unsuspecting person to ‘pick’ seeds from a mature fruit!

Spotted Jewelweed & Spotted Touch-me-not – flowers have red spots on petals.

Lady’s Eardrops – refers to the shape of the flower.

 

Scientific names:
Impatiens – refers to the impatient, explosive nature of seedpods, which can disperse seeds two feet or more away from the parent plant.

Impatiens capensis, actually a native North American species, was mistakenly thought by Nicolass Meerburgh to be native to the Cape of Good Hope, in southern Africa. Africa is home to many Impatiens species, but not this one or Impatiens pallida that can also be found in the Abbott Marshlands, especially along Lamberton Road on Duck Island.

The name Impatiens biflora, found in some older reference books, is superseded by I. capensis. The ‘biflora’ refers to the two types of flowers a plant can produce. These are showy orange flowers with an elongated spur, often with red spots, and small inconspicuous flowers. The showy flowers require a pollinator, while the small ones are self-pollinated.

Flowers:
The technical name for the large, showy cross-pollinated flowers is ‘chasmogamous’.

The other type is small, green, and inconspicuous; these never open, self-pollinate, and are called ‘cleistogamous’ flowers.

The showy flower has a landing platform for insects formed by the two lateral petals, and a tubular nectar spur, which is a sepal. The showy flowers, while having both male and female parts, assure that cross-pollination occurs by an extraordinary process. When a showy flower opens, it is functionally male because the anthers are united around the stigma and form a covering over it. After the male phase, which lasts for ~ 24 hours, the anther cap falls off exposing the female stigma. The flower is in the female phase for ~5 hours. It is during the female phase that pollination, leading to seed production, can happen. During the male phase, pollen is picked up when a visiting insect or hummingbird is dusted with pollen from the anthers. The pollen is carried to a flower on another plant that’s in the female phase. Cross-pollination appears essential for the production of seeds in showy flowers.

The anther cap is dislodged by elongation of the ovary. Nectar is produced in the spur and is about 40% sugar and contains 25 amino acids. The mix of amino acids contains all but one of the 16 considered essential for insect nutrition.

How do pollinators locate flowers? Insects can ‘see’ ultraviolet light; and reflection patterns show that the spur, the inner surface of the petals, and the anthers reflect UV light. The principal insect visitors in a Delaware study were of four types: pollinators (10 species), primary nectar thieves (6 species), and secondary thieves (21 species; some of these take nectar from a hole made by a primary thief, and others are small enough to pass under the anther cap or stigma while taking nectar). The most abundant pollinators were bees (Bombus vagans, B. impatiens, Apis mellifera) and the yellow jacket (Vespula maculifrons). The only bird visitor was the Ruby-throated Hummingbird, which is attracted to flowers by color and sees the red dots on the petals.

Compared with the showy chasmogamous flowers, the inconspicuous cleistogamous flowers, are reduced in size, as is the number of pollen grains. The pollen apparently begins to germinate while on the anther, and because the parts are so close together, the pollen tube grows and penetrates the stigma. Fruits produced by both types of flowers are similar, but those from the cleistogamous flowers are usually smaller and contain fewer, smaller seeds.

So, why does this species produce small self-pollinating flowers? The smaller flowers are about a third to half as ‘expensive’ for a plant to produce. Therefore, even if resources are limited, plants in stressful habitats can still produce seeds for the next year. Resource-limited habitats may have low light or are places that tend to dry out during the summer. Most Jewelweed populations produce both types of flowers, but those that produce only small cleistogamous flowers retain the ability to produce showy flowers if they’re grown where conditions are optimal.

Jewelweed is an annual species, dependent on seeds for survival from one year to the next. There are virtually no seeds remaining in the soil after spring germination.

Seeds:
It was quite a circuitous route, but Jewelweed is the plant that led me to the Abbott Marshlands. I first noticed seedlings on the bottom of a stream in western Massachusetts in April many years ago while visiting my folks. This led me to wonder about O₂ requirements for germination. Several years later I began my first germination study, which involved many treatments, including +/- light, several temperatures, scarification (nicking the seed coat), and several concentrations of gibberellic acid (a growth hormone). The oxygen concentrations came later. I had collected seeds in autumn, stored them in a glass jar, and placed them on the lab bench until the following spring semester was finished. Of hundreds of seeds, nary a one germinated, while those that I’d left with my mom in her refrigerator and that she watered when she remembered, germinated! That germination failure put me on notice; after that I set up germination studies soon after harvest or provided optimal storage conditions: seeds of this facultative wetland species cannot be dried.

Subsequent germination tests showed that seeds require oxygen for germination and, in fact, are killed if subjected to anaerobic conditions for a period of time. This is easy to test: place seeds into a small jar and, because seeds float, make a small sac of netting (a piece of an old nylon works), add a small clean stone or marble to weigh it down, fill jar to the brim with water, close the lid tightly eliminating bubbles, place it in your ‘frig’; this has little available oxygen. Compare what happens with a second set of seeds that receives oxygen: set these seeds on a piece of very moist paper towel in a small jar, loosely cover the jar and remember to add water to the paper from time to time. After about 4 months remove the lid of the first jar and dump off most of the water; check the second jar. The seeds in the anaerobic jar will not have germinated in contrast to those in the second jar with oxygen.

 

Jewelweed seeds have some apparent peculiarities:

Below the brown seed coat, there is a turquoise blue layer. Reports indicate that white-footed mice feeding on Jewelweed seeds have blue tummies. (I personally have not seen this, but Charlie Leck has).

Seeds can float for more than 2 months. Evidence for this ability to float, can be seen where seeds have drifted and collect along the edge of a log where they germinate in dense groups. (See photo).

Seed dispersal is also from the explosive fruits.  Studies have shown that energy storage is greater than of elastin (elastic protein in connective tissue) and spring steel. Video studies have documented that the process of dispersal is very rapid.

Seeds need to experience moist cold storage, called stratification, for 3-4 months. This allows chemical changes necessary for germination even in a refrigerator. The process can be halted by storing just at freezing and then germination can be timed to coincide with a desired planting time. A test showed that after stratification at 41 F (5C), germination was more than 85%, but at 50 F (10 C) it was only 25%.

Seeds do not tolerate prolonged inundation and low oxygen levels; they die. My observation of seedlings in a stream was probably a fluke; the seeds may have germinated along the stream edge and then seedlings fell into the water.

Seeds do not tolerate drying.

Light is not required for germination.

Seeds from the Abbott Marshlands tidal marsh were 4.2 times larger than those from a low light environment (in a study that compared eight populations from central NJ); seedlings were also larger. The large size of seedlings is an advantage in a habitat where growth is rapid.

Germinating seeds produce a ring of roots rather than one main root; this feature, noted in many mudflat species, provides anchorage and stability in a ‘liquid’ substrate and allows root development at the aerobic mud surface. The tips of the roots are red; the adaptive value of this is not known.

Seeds are edible and reportedly taste like walnuts. Groups of seedlings can be found in the spring where seeds collected by mice were cached, and then left uneaten.

 

Jewelweed Uses:
Jewelweed stems can be crushed and sap used as an antidote for poison ivy, insect bites, and nettle stings. As noted, seeds can be eaten; the showy uncooked flowers can be eaten in salads or cooked in stir-fry. Some websites indicate that stems and leaves can be eaten if boiled for 15-20 minutes with two changes of water.  Frankly, I’m leery of plants that need to be boiled and water changed twice to remove high amounts of calcium oxalate and selenium!

Photographer Lucas Foglia reports that some people use flowers for making soap (pers. communication, Aug. 2019).

 

References:
https://homeguides.sfgate.com/jewelweed-edible-104968.html

Eastman, J. & A. Hansen (Illustrator). 1995. The Book of Swamp and Bog. Trees, Shrubs, and Wildflowers of Eastern Freshwater Wetlands. Stackpole Books. Mechanicsburg, PA.

Hayashi, M, KL Feilich, and DJ Ellerby. 2009,  The mechanics of explosive seed dispersal in orange jewelweed Impatiens capensis). Journal of Experimental Botany 60: 2045-2053,

Leck, MA. 1979. Germination behavior of Impatiens capensis Meerb. (Balsaminaceae). Bartonia 46: 1-14.

Rust, RW. 1977. Pollination in Impatiens capensis and Impatiens pallida (Balsaminaceae). Bulletin of the Torrey Botanical Club 104: 361- 367.

RL Simpson, MA Leck, VT Parker. 1985. The comparative ecology of Impatiens capensis Meerb. (Balsaminaceae) in central New Jersey. Bulletin of the Torrey Botanical Club 112:295-311.

Mary Allessio Leck
August 22, 2019

 

Marsh Meandering  I.  Wild Rice
7 June 2019

A walk along the D&R Canal Towpath trail at low tide revealed small sandbar islands that are now well vegetated with wild rice (Zizania aquatica) seedlings already more than a foot tall.  It’s the only grass growing in that habitat.

This annual, an obligate wetland species, can grow to more than 10 feet by the end of the growing season. After flowering in August and setting seed, it will die. Its seeds are a favored food of many birds including black birds, such as Red-winged Blackbirds and Grackles, and migrant ducks.

Interestingly, there is no evidence of use of Wild Rice by Native Americans in the Delaware River Valley although northern tribes used it extensively.  Much of what’s sold commercially is grown in Minnesota and California.

The slender seeds are more than one inch long with a needle-like extension, called an awn, making up part of its length. From this seed first emerges a seed structure, known as the hypocotyl, and then the shoot. Roots take a bit more time. As human food, they are gluten free, and provide fiber and various nutrients.

Seeds cannot be dried. Early colonists were not successful in bringing them to Kew Gardens in England until it was discovered that seeds needed to be stored in water.

Wild Rice can be found in wetlands throughout the Abbott Marshlands. Young plants can tolerate being inundated. Look for them in mucky, muddy places, the bottoms of small tidal streams, shallow ponds, and in the abandoned canal along the towpath trail where in spring there are often dense grouping of light-green grass plants.

When Wild Rice flowers, male flowers are below the female ones. The yellow male flowers make the plants conspicuous.  Flowering is from late July to September.

 

This is one of the food plants for caterpillars of the Broad-winged Skipper. Adults (~0.8 inch) obtain nectar from dogbane, swamp milkweed, pickerelweed, thistles, etc.

Broad-winged Skipper (Wikipedia)

Botanical facts: The Wild Rice species found in the marsh is Zizania aquatica a member of the grass family (Poaceae) like corn or your lawn grass. There are three other Zizania species: Z. palustris is found in northern areas (Minnesota, Wisconsin, Canada) and Z. texana, a perennial species now endangered, occurs in central Texas; Z. latifolia, Manchurian Wild Rice, now rare in nature is native to Asia, where it is cultivated for its stems that are eaten as a vegetable.

Like corn, Wild Rice is monoecious, with both male and female flowers on the same plant, but in Wild Rice, the male flowers, where pollen is produced, are located below female ones.  Male flowers are typically yellow, but may sometimes are reddish.

Because of the economic value of wild rice for human consumption, much research has been focused on learning how to germinate seeds. Early work showed that seed dormancy can be broken by prolonged cold treatment (e.g., 3-6 mo at 1-3 C; 21-37 F) at low oxygen levels, as would occur if submersed in water or in mud at the bottom of a tidal stream. (Although many factors can influence the actual amount of oxygen in water such as temperature and wind, the content of air is 20%, while that of water is 1%, which is why people drown).

Seeds can remain dormant for more than a year. This can account for field observations that some years in some locations in the Abbott Marshlands there may be few or no Wild Rice plants. Long seed dormancy poses problems for plant breeders who desire multiple crops per year, and for growers who wish to change varieties in established fields.  However, freshly harvested seed can be germinated, if first dehulled by scraping and stored 1-4 weeks at 1.5 C (35 F).

 

 

Resources:
For tides, consult the marsh website (www.abbottmarshlands.org -Tides) or local newspapers.

Background and for use of Wild Rice by Native Americans and other background see https://en.wikipedia.org/wiki/Wild_rice

For use in the Delaware River Valley:
Messner, Timothy. 2011, Acorns and Bitter Roots: Starch Grain Research in the Prehistoric Eastern Woodlands. University of Alabama Press, Tuscaloosa. (p. 21).

Also: Personal Communication, Michael Stewart, June 10, 2019.

Germination and growth
Cardwell, V.B., E.A. Oelke, and W.A. Elliott. 1978. Seed dormancy mechanisms in Wild Rice (Zizania aquatica). Agronomy Journal 70 (3): 481-484.

Whigham, D.F. and R.L. Simpson. 1977. Growth, mortality, and biomass partitioning in freshwater tidal populations of wild rice (Zizania aquatica var aquatica). Bulletin Torrey Botanical Club 104: 347-351.

 

Mary A Leck,
Emeritus Professor of Biology, Rider University
Friends for the Abbott Marshlands

info@abbottmarshlands.org

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