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Home , Seed dispersal

[email protected]  how do travel? slide show script prepared by Richard Carstensen for Discovery Southeast Original 1990, updated 2007

Note to Discovery naturalists and teachers . Tiny (see above I used these slides in my third and fourth grade Nature Studies program at Harborview in the early 1990s. The script definitions)of mushrooms, however is written at a high school level, to provide you with mosses and also are precise information should you need it. Middle and grade school moved about in the air. teachers can easily adapt the script for their students by replacing Most which the italicized technical words with the simpler words offered in parentheses. You may wish to present some of the technical words live partly or entirely in the in a separate class before viewing the slides. water have seeds which float. At Harborview I prefaced this slide show with a discussion They can be moved about on of possibilities for dispersal. Most strategies are intuitively obvious, and can be elicited from the class just by asking the right the currents. questions, like: How might a seed be shaped so that it could hitch- “Unspecialized?” It’s hike a ride in an animal’s fur or feathers?, pretty hard to imagine how Or: How could a seed travel inside an animal and still survive? (Be prepared for giggles and horrified locks when you ask this one. the seed of a plant like beach I plan an extra several minutes to let hysteria and wisecracks run pea gets around. It must have their course before proceeding. This paves the way for more casual some tricks we don’t yet understand! discussions when we get into scat in our winter tracking classes.) The very last slide requires familiarity with the use of tables, Animals Seeds can use animals either by hitch- and a fairly advanced logical facility. I don’t use it in third grade, and hiking a ride on their fur or feathers, or by being eaten, even in fourth grade when we examine strategies and somehow not being digested, but surviving in their in the context of our different natural communities, teachers report a wide range in comprehension of the table. It’s probably most scat. appropriate for middle and high school classes. In third and fourth grade I don’t get too technical about what 3) Dwarf fireweed a seed actually is. In fact I don’t distinguish between seeds and seed spores. But you may wish to begin your discussion with these basic definitions. A seed is the fertilized of the ‘higher” or flowering Dwarf fireweed and plants, composed of an with a food supply. A is like a seed but consists of a reproductive cell (usually a single cell), its cousin tall fireweed lacking a food supply, and found In the ‘lower plants like mosses have plumes attached to and ferns, and in the fungi (eg. mushrooms). Spores tend to be their seeds which allow smaller than most seeds. them to travel for miles on breezes. This slide shows an area about one 1) Title slide centimeter across -- the The illustration on this scale is in millimeters. What other plants do you know opening slide is of 2 Sitka which have plumed or fuzzy seeds? (Answers Dandelion, spruce cones, showing the willow, cottonwood.) size range. covering the seeds are shown above, 4) Licorice with the winged seed itself Thesori (small paired in the center. dots) on the underside of this licorice fern each 2) Dispersal illustration contain thousands of There are at least 3 ways that a seed can take spores, too small to see, advantage of the wind. One is to have a wing, like the so tiny they easily float spruce seed. Another is to have a fuzzy, or plumed seed, in the air. To get an like dwarf fireweed. And many plants have such tiny idea of the size of these seeds that they need no attached wings or to float spores, let’s zoom in on a about in the air. Wintergreen is one such flowering few of the sori.  • [email protected] 9) Seeds at high tide line 5) Closeup Seed of salt marsh plants This entire slide shows drifts up to the high an area only about one tide mark and often is centimeter across. These deposited in huge piles. 8 sori each contain about This is one of the many fifty little spore packets. features that makes the The packetsthemselves drift or debris zone so contain hundreds of attractive to birds and spores, and will soon split mammals. The seeds in this photo are of Lyngbye sedge, open to release them. a salt-tolerant grass-like plant that produces bushels of seeds in the fall. 6) Alder, spruce and hemlock “cones” Several of our have 10) Pondweed winged seeds, borne inside Freshwater aquatic plants cones. Winged seeds can’t produce and travel so far as plumed or seed heads at the water fuzzy seeds, so perhaps it surface, and when seeds makes sense that they’re are released they drift found on trees that can about on the surface. The release them from high in the air where they get a “head floating seeds can also start.” become attached to the The pair of cone-like in the upper left are plumage of waterfowl, and carried to distant . from an alder. In the upper right is a spruce cone. The Newly created ponds quickly become colonized by hemlock cone at bottom is shown in different stages plants like the pondweed in this photo, brought in as of opening. As the scales spread apart on dry days seeds stuck to the feet and feathers of ducks. the winged seeds fall out, and spin rapidly, which can sometimes carry them hundreds of feet from the parent 11) . The next slide shows seeds of these 3 trees, in the Here are 5 of our same positions as the cones in this view. common -like 7) Closeup of seeds fruits. Clockwise from the upper left they are: Alder seed has 2 wings, blueberry, strawberry, spruce and hemlock seed elderberry, twisted stalk each have just one. Alder (or watermelon berry) and seed is the lightest, and can devil’s club. One of each carry the farthest on the of the berries has been wind. sectioned to show the seeds, although this isn’t necessary for strawberry, which bears its seeds on the surface of the 8) Goosetongue . A berry is costly for a plant to produce, and the Most of the plants that whole purpose of berries is to be eaten. The juicy part of grow in our salt marshes the fruit is digested, and the hard seeds are carried about (intertidal wetlands) have and eventually excreted by animals. The following slide floating seeds. Here is the shows the seeds of these berries, arranged in the same delicious goosetongue, positions. at high tide, with its seed heads about to be 12) Closeup of seeds submerged. Clockwise from the upper left these are seeds of: blueberry, strawberry, elderberry, twisted stalk (or watermelon berry) and devil’s club. The 2 huge seeds [email protected]  in each devil’s club berry into nearby . occupy almost the entire Sometimes a large patch fruit, and are not favored of bunchberry is a by people, but highly single plant, connected sought by bears and birds. by runners. Of course Seeds in berries usually the seeds in bunchberry have hard coats that resist also are dispersed by the digestive enzymes in animal’s stomachs, and even birds like blue grouse, so the powerful grinding action of grit- filled bird gizzards. the plant has more than one option for dispersal. What Many can pass through the animal and survive in its other plants colonize by runners? (Answers, strawberry, scat. trailing raspberry, many grasses and sedges.)

13) Bear scat with soapberry seeds 16) Sidewalk plantain The comb in this picture is Here is one of the few for scale. It’s 5 inches long. plants that survives The darkened area in the in school yards and center is where the mosses along sidewalks, highly were killed the previous resistant to trampling. autumn by a bear scat. It always seems to be The scat was composed found near human mostly of soapberries, , and in fact which don’t grow near it probably relies mostly Juneau but are common in Glacier Bay and Haines. The on people to distribute its seeds. These are shown in the pulp from these berries washed away long ago, but many next slide. of the large black seeds can still be seen. The small green sprouts clustered near the comb are baby soapberry 17) Plantain seeds plants, thriving in the nutrient-rich seed bed. The seeds of plantain

14) Forest seed cycle when moistened develop a clear sticky coating or This collage shows several “glue” which adheres to stages in the life cycle of a red shoes. Its easy to watch huckleberry plant, and 2 of this by placing several the animals–varied and seeds in a drop of water brown bear–that help move for about ten minutes, its seeds. In the lower left is and then studying them with a hand lens. a berry that was chewed by a deer mouse, revealing the 18) Hitchhikers seeds. Just above it is a first year Plant seed that catches sprout, only a few millimeters on fur or feathers could high. Sometimes hundreds of these sprouts germinate be called hitchhiking in a single bear scat, but only a few will survive to the seed. The seeds on this creeping evergreen-leaved stage, shown in the lower pile jacket are, clockwise right. And of these small evergreen huckleberries, only from upper left: cotton those receiving enough light will grow into fruiting sedge, large-leaved bushes, like this one, shown in fall after the leaves have avens (with some of dropped. the individual seeds teased out and placed next to the

15) Vegetative spread seedhead), squirreltail grass and bedstraw. All have attachments that help the seed adhere to fuzzy surfaces. Many plants can colonize new places without relying Cotton sedge is mostly carried by the wind, like willow on seed reproduction. Bunchberry or ground dogwood and fireweed, but is also animal distributed. Avens has has runners or underground stems that simply grow a tiny ‘fishhook’ on each seed, barely visible in this  • [email protected] photo. Squirreltail grass seed has a “spear” that often penetrates fur or clothing, and bedstraw seeds resemble little velcro balls. Hitchhiking seeds are found mostly in our meadow, or early successional communities, and are relatively uncommon in forest habitats.

19) Seeds and pods of meadow plants These seeds may have sophisticated dispersal strategies, but we haven’t figured them out yet. Far from being designed for easy wind dispersal, they might be described as “bomb seeds”. Clockwise from upper left: lupine, yellow rattle, black lily, beach pea and iris. In some cases heavy round seeds may be needed to penetrate the meadow’s moss layer, in order to reach mineral soil where they can germinate. A large heavy seed can also carry more food to get the seed started. This is important because the sprout may need to grow several inches tall before it emerges from the moss into the sunlight, where it can begin producing its own food through .

20) Communities table Do seed dispersal strategies differ in our different natural communities? Sure! For example, notice on this chart how many berry-producing plants grow in the old-growth forest. What other patterns do you notice on this table? Would you expect more plants to rely on wind distribution in the forest or in open habitats like meadows? Should plants with winged seeds be taller than the other species in their community?