LARRY H. KLOTZ, 1992 25
On the Biology of Orontium aquaticum L. (Araceae), Golden Club or Floating Arum
Larry H. Klotz Department of Biology Shippensburg University Shippensburg, PA 17257, USA
On May 16, 1982, I visited a group of the Orontium inhabits sandy, muddy, or peaty small, natural ponds that are abundant near soil (Ogden, 1974) in many types of shal my home in the Appalachian Mountains of low freshwater wetlands or their moist banks southcentral Pennsylvania. As I entered the and shores: cold mountain spring runs first pond, I was surprised by a spectacular (Strausbaugh & Core, 1977), freshwater tid display: a large population of golden club al wetlands, seeps (Tiner, 1988), pools in full bloom (Figs. 1 and 6). The time was (Godfrey & Wooten, 1979), sloughs late afternoon, when the low angle of the (Harshberger, 1970), marshes (Beal, 1977), sun made the inflorescences· seem like bogs (Radford et al., 1968), rivers (Hell glowing white candles in a lake of black quist & Crow, 1982), streams, ponds, lakes, water. I could then visualize a description and swamps (Beal & Thieret, 1986). It has published 72 years earlier by Witmer Stone been observed to grow in depths as great (910): "The Golden Club is one of the as 12 to 15 dm a. C. French, pers. comm.). attractions of the [New Jersey] Pine Barrens The water in which it occurs is typically in springtime, when the surface of the pools acidic and "organic" (tanniniferous). The bristle with its brilliant, slender, orange measurements of pH from the habitats of yellow spikes bordered below with white Orontium in North Carolina have a median where they join the green stalks ...." value of 6 (somewhat acidic) and range from Orontium aquaticum, the sole species slightly less than 5 to slightly above 7 (just of the genus, is a highly distinctive aroid. above neutral) (Beal, 1977). Its closest relatives are probably the skunk The population depicted from southcen cabbages, Symplocarpus and Lysichiton tral Pennsylvania dominates a shallow, sea (Barab€! & Forget, 1987; Grayum, 1990), sonal pond that commonly lacks standing which also inhabit North Temperate fresh water (but remains moist or muddy) from water wetlands (Krause, 1908; Huttleston, midsummer through midautumn. In the 1953). Orontium is endemic to the eastern Appalachian Mountains of central Virginia, deciduous forest biome in the United States, a large population of Orontium occurs in primarily on the Coastal Plain and less fre a Sphagnum-lined, spring-fed pond (Raw quently in the Appalachians, where it linson & Carr, 1937) that maintains rela reaches an elevation of 850 meters (Hut tively constant water levels (Virginia Nat tleston, 1953). The range of the species ex ural Heritage, unpubl. data). In the tends from Massachusetts and central New Okefenokee Swamp in Georgia, Orontium York to Kentucky, Florida, and Louisiana prevails under inundated conditions in a (Grear, 1966; Godfrey & Wooten, 1979). It marsh that undergoes drawdown only dur is generally rare or local in the northern ing drought years, which are infrequent and and western parts of its range (Beal & unpredictable (Greening & Gerritsen, Thieret, 1986; Hellquist & Crow, 1982; 1987). Hough, 1983; Huttleston, 1953; Ogden, Orontium is a perennial herb with a stout, 1974; Weatherbee & Crow, 1990). In Penn firm rhizome (Figs. 2 and 3). The rhizome sylvania it is considered rare and seems to is often deeply sunken because it produces be declining. The population depicted here contractile roots, which pull it into the soil is one of the largest in the state. (Hotta, 1971; French, unpubl. data). The 26 AROIDEANA, Vo l. 15
Fig. 1. Natural population of Orontium aquaticum in a seasonal pond along the base of South Mountain, Franklin County, Pennsylvania.
shoot has a definite organization: each seg hances the diffusion of gases in the interior ment bears three foliage leaves (Ray, 1987). of the organs [Sculthorpe, 1967].) The up Above these is one inconspicuous bractlike per surface of the blade is dark, velvety, leaf, often designated as the spathe (e .g. matte bluish green. It strongly repels water Wilson, 1960). It sheaths the base of the and contains the stomates, which are over inflorescences but is sometimes deciduous arched by the surrounding epidermal cells by the time of anthesis (Brown & Brown, (Grear, 1973; French, unpubl. data). The 1984). Each segment of the shoot termi lower surface is pale, glossy, and silvery nates in a pair of inflorescences, one arising green wi th numerous, fine , dark green par from a bud on the base of the other. One all e l ve ins and a broad, whitish, protruding or both of them often abort at an early stage midrib, which extends from the petiole to of deve lopment (Ray, 1988). The stem is the leaf tip. The leaves do not noticeably continued by a branch from the axil of the emit a musky odor when crushed or bruised uppermost foliage leaf (Ray, 1987). There as do some Araceae, such as Symplocarpus. are no resting bud scales even though the The leaves are not evergreen but instead species is temperate (Ray, 1988). wither when the plants enter dormancy in The leaves are either emersed or fl oating, autumn. depending on the depth of the water. Their The season of fl owering and leaf expan buoya ncy results from large intercellular air sion ranges from March and April in the spaces, which impart a spongy texture. southern part of the range to May and June (Such "aerenchyma" tissue occurs in most in the northern part (e.g. Hough, 1983). In emergent aquatic plants. Besides providing southcentral Pennsylvania, flowering oc buoyancy and mechanical strength, it en- curs from early April to mid-June and peaks LA RRY H . KLOT Z, 1992 27
Fig. 2. Basal portion of excavated plant; the white leaf bases indicate the depth of sub mergence in the soil. 28 AROIDEANA, Vo l. 15
Fig. 3. Rhizome with adventitious roots.
about mid-May. Inflorescences at va ri ous spadices placed in a jar p roduce a percep stages of fl owering and immature fruit can tible fo ul, fungal odor a. c. French, pers. occur simultaneously on a single plant. comm.) , which may serve as an attractant The spadix is concealed by the fl owers, fo r fli es or beetles (Grayum, 1990) . It would which adj oin each other in a hexagonal or be interesting to determine whether the rhombic pattern (Fig. 7). The fl owers are spadix generates heat during fl owering, as all bisexual (Huttleston , 1953; Krause, it does in some other Araceae, such as Sym 1908), or they are bisexual at the base of p locmp us (Grayum, 1990), the spadix and intergrade to staminate to The pollen grains of Orontium lack starch ward the tip (Bogner, pers. comm.; Schaff and are relative ly large (mean of longest ner, 1937), Meiosis apparently occurs in the diameter: 64 /-Lm ) . In the Araceae, starchless fl ower buds sometime during the sum pollen is associated with pollinati on by bees mer- more than eight months in adva nce or fli es (Grayu m, 1985) while large pollen of anthesis the following spri ng (Grear, is correlated with pollination by bees or 1966) . Anthesis occurs in ascending se beetl es (GraytIlTI , 1986). The type of pollen quence on the spadix. sculpturing in Oron tium (foveolate- retic Orontium is stated to be entomophilous ulate- GraytI111 , 1985) is considered to be (Cook, 1990), but published data on pol unspecialized for particular pollinators but lination are lacking (Grayum, 1990) , Vari· is associated with pollinati on by bees, fli es, ous insects (e.g. dragonfli es) perch on the and beetles in this fa mily (Grayu m, 1986) . spadices but may be using them simply as The peri anth is green when the fl owers landing sites ( P. B, Tomlinson , p ers. are very young, turns yellow before and comm.) , I have not detected any odor from during anthesis, and becomes green again a single spadix, but numerous fl owering during fruit development. The ye ll owing is LARRY H . KLOTZ, 1992 29
Fig. 5. Bisected fruits , showing pericarp Fig. 4. Infructescence with mature fruits. and emblYo; the emblYo characteristically contains a small cavity. due to a decrease in chlorophyll concen tration rather than an increase in ca rot is green and often partly brown or dark ma enoids (Casadoro et ai., 1982) . In fl ower roon, especially distally. The inner surface and immature fruit, the tips of the tepals is whitish. The seed is globose, 6- 10 mm are sharply folded over the ovary. Growth in diameter. Its surface is dark green and of the fruit straightens the tepa Is and hides has no obvious seed coat except for the the stamens, which persist beyond fruit ab slimy covering described above. No endo scission. sperm is present in the mature seed (Gra The spadix is borne on an elongated yum, 1990) . The mature emblYo is firm -tex scape, whi ch is white distally and erect or tured and pale green (or sometimes yellow) ascending during fl owering (Fig. 7). After internally, except toward the distal end, anthesis is completed, the scape becomes where it is creamy white and contains a green and grows downward so that fr uit small , smooth cavity. maturati on occurs in the water. The scape I have observed ripening of the fruits and the spadix disintegrate after the ripe during June and July in southcentral Penn fruits abscise. sylvania, but it is reported to occur during The ovalY contains a single, basal ovule. July and August in New Jersey (Hough, Hairs on and around the ovule probably 1983). The fru its are "probably mostly an produce the mucilage that oft en fill s the imal dispers ed" (Cook, 1990). They detach entire 10Clde and is conspicuous as a clear, from the spadix when ripe and are able to sli my, jellylike covering on the mature seed. fl oat. Their buoyancy results from air spaces After pollination , the mucilage may pro in the pericarp: the seed sinks immediately vide a medium for pollen tube growth be if the pericarp is removed. Ridley (1930) tween the style and the ovule (French, observed that after the fruits have fl oated 1987) . The ripe pericarp is fl eshy but rel for about a week, they sink as the pericarp atively thin (Figs. 4 and 5). Its outer surface becomes water-logged and that after anoth- 30 ARO IDEANA, Vo l. 15
Fig. 6. Natural population of Orontium aquaticum in a seasonal pond along the base of South Mountain, Franklin County, Pennsylva ni a. er week, the peri carp splits at the apex and If dried, the seeds shrink greatly and die releases the seed. (Cook, 1987). They are relatively heavy In the populati on depicted, I have ob compared to those of other aquatic plants: serve d that the see d ~ can germinate within only 5,500 dried seeds per kg as compared the fr uits as they mature on the spadix in to 33 1,000 per kg in Ca lla p alustris or late June: the fi rst three plumular leaves 386,000,000 per kg in Utricularia cornuta emerge near the base of the seed and curve (Muenscher, 1944) . I obtained a value of around it, between the seed coat and the 17 percent dlY mass from a sample of 100 peri carp. I have noti ced a few instances of seeds, and they lost an ave rage of 42 per complete vivipalY: the pericarp had split cent of their diameter on dlying. and the plumular leaves had become ex Like other Araceae, Orontium has pack posed before the fruit abscised from the ets of needle-like Clystals in almost all ti s spadix. (Among the seed plants, vivipary is sues. The Clystals defend the plant against chiefl y characteristic of mangroves [Tom herbivory when it is eaten raw. When the li nson, 1986].) The plumular leaves are Clystal-containing cells are broken, they ab green, slender, tapering, and blade less, with sorb water and discharge the Clystals, which an adaxial groove in the basal part. The penetrate the tissues of the mouth and cause outermost leaf can attai n a length of about intense irritati on (Wilson, 1960) . (I have four cm before the seed is released fro m experienced such burning when touching the pericarp. The radicle has also emerged my face while dissecti ng the fruits of Oron by this time but is short (1 mm) and whit tium.) Drying or prolonged cooking de ish. At least some of the seedlings become activate these cells and so remove the acrid rooted in this population: I have observed pepperiness (Peterson, 1978; Wilson, 1960) . them to be abundant during the summer. The rhizomes and seeds are starchy and LARRY H. KLOTZ, 1992 31
Fig. 7. Inflorescences. were a source of carbohydrate for the Amer of water in a sunny location and should be ican Indians (Sculthorpe, 1967). After be given a rooting medium enriched with fer ing thoroughly dried, these parts can be tilizer (Raffill , 1946). Propagation is chiefl y ground into a nutritious, mealy fl our. Al by seed or by dividing the rootstocks at ternatively, the dried seeds can be boiled planting time in early spring. The plant may for 45 minutes in several changes of water be difficult to eradicate once it is estab and served like peas (Peterson, 1978). I lished where the rhizomes can grow fr eely have eaten a few fr esh , mature seeds after (Bailey, 1929) . microwaving them fo r fi ve minutes in tap water. They had a firm texture and a pleas ACKNOWLEDGMENTS ant, nutty fl avor; they caused me no irrita This article was ori ginally published in tion. German, in a translation by Josef Bogner Because Orontium requires only shallow (Klotz, L. H. 1991. Ueber die Biologie von water and fo rms a compact clump, it is suit Orontiu m aquaticum L. (Araceae), del' able fo r small ornamental pools, where it Goldkeule. Aqua-Planta 4-91:131- 138.) . I can be grown with smaller, more delicate am grateful to Josef Bogner, P. Barry Tom aquatics. The plant requires little attention linson, and James C. French for their com and can fl ourish for many years in the same ments and suggestions. Shippensburg Uni soil, but specimens grown in pots or tubs versity provided support for interlibrary should be divided and replanted every two loans and a computerized bibliographic or three years (Everett, 1981). Because of search (DIALOG). I especially thank the its firm hold on the soil , Orontium may be landowner and the ne ighbors of his prop planted in swifter water than most aquati cs. erty for protecting this population of Oron Rhizomes should be planted in 3 to 5 dm tium and allowing me to study it. 32 AROIDEANA, Vol. 15
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