Perhaps one of the most distinctive, easily spotted and identifiable shrubs in our area, the singular Ceratiola ericoides plots a narrow distribution. If you’re on St. George Island, back in the oldest hind dunes (on the bay side) in the State Park or spotting some of the few remaining stands of Sand Pine (Pinus clausa) scattered down the island, watch for dense, dark green, increasingly spreading evergreen shrubs that are no taller than 5 feet. They will often be somewhat isolated from other vegetation, thus standing out in the landscape. You’ll never see conspicuous flowers, indeed the only evident change will be seasonal (January-March) ranks of small, spherical, yellow fruit (drupes with 1-2 seed) covering 2-year old branch segments on female plants. Yes, this is another dioecious plant in the local Flora.
Consulting the ISB distribution maps, it appears Ceratiola is coastal along the central Panhandle, as well as on the Atlantic side into South Carolina. The most extensive populations, however, will be found inland, in sandy hills down the Florida Peninsula, as well as along the Fall Line in mid-Georgia, marking xeric habitats and perhaps representing ancient persistence.
Here on St. George the plants are abundant, in narrow lens-shaped patches of what in other parts of the state would be Florida Rosemary Scrub, a distinct vegetation type with predictable associates, such as Eryngium, Calamintha, Liatris, Polygonella, and of course Pinus clausa (Quintana, et al, 1996). In core areas of the Peninsula, as well as Georgia-South Carolina, you’ll find reasonably well-studied associations, though the most complete reports generally do not mention Panhandle populations. We are, afterall, the Forgotten Coast, which is fine by me. But also, I’m thinking the associations that include Ceratiola here may not be as seemingly definitive as the Florida Scrub or LongLeaf Pine Turkey Oak in Georgia. Our plants are clearly considered peripheral to the South Florida center of distribution for the species.
I say “species” so unequivocally because this is a rare situation when there’s no confusion or taxonomic complication. André Michaux described observations from Georgia and Florida in his 1803 Flora Boreali-Americana, which pretty much tell the entire story. I’m pasting his copy below in order to document how well he knew the plant, an understanding that hasn’t been challenged.
Ceratiola ericoides, the names Michaux selected, are almost singular in having stood the rigors of taxonomic time. Floras, ISB, and POWO indicate only two known synonyms, one published by Italian botanist Bertoloni in 1853, the second by French botanist Gandoger in 1919. Bertoloni illustrates the Gates’s specimen (from Alabama), which he described as Empetrum aciculare (see below). The other, a segregate species Ceratiola falcatula, proposed by Gandoger. Neither has impacted the uninterrupted use of Michaux’s name, and nothing has challenged his suggestion as to relationships.
What was Michaux telling us with his genus and specific epithet? Wayne Elisens’s Flora of North America treatment states the genus name, Ceratiola, references the “horn-like” appearance of the tapered styles. The specific epithet, “ericoides”, was Michaux’s reference to the vegetative resemblance of these shrubs, with their needlelike foliage, to Heaths, like the Mediterranean Erica arborea. Here’s the illustration accompanying Elisens’s treatment in Flora of North America.
The illustrations are more useful than most descriptions. Floral details in Michaux’s description and elsewhere will not help much in the field. Currently considered Ericaceous, you mightn’t expect that relationship lacking familiarity with some the plant’s distant Heath relatives in distant lands. But drawings and photographs are diagnostic. Below is yet another drawing, not clean but interesting, from an early field study, completed by J. C. Th. Uphof (1932)
Research and publication on Ceratiola biology and ecology is extensive, with most studies focusing on distribution, community dynamics, fire ecology, conservation, recruitment, and allelopathy. In Citations & Notes I’ve extracted and summarized the import of many of those publications, and may add more over time. But the literature is extensive and technical, so there’s a true limit in both my available time and mental capacity to thoroughly review and comprehend that information. There’s much to digest, so here are some points that may be of greatest interest to naturalists:
Biology: As mentioned above, the plants are reported conclusively to be obligately dioecious. There has been no evidence of monoecy or conversion in differing life stages. Plants flower in autumn on growth produced the previous spring. Flowers are highly reduced. I missed this past year’s flowering and will have to wait until next September to secure photographs, but drawings show us the female flowers are basically an ovary with conspicuous styles, while the male flower consists of two pendent stamens. The plants are reported to be wind pollinated, one additional specialization that makes me wonder why Ceratiola and its few relatives are retained in the Ericaceae.
Fruit develop the following year, such that at maturity (January-March), a female plant will show an upper stem segment (2-several inches of stem) with remains of the most recent flowers tucked tightly into leaf axils, while the small, pale yellow, somewhat fleshy spherical drupes mature on the previous year’s growth.
Culture & Conservation: Ceratiola can be propagated, both vegetatively and from seed. Compared to most horticultural plants, the process is slow. Seed may take a year to germinate. Johnson (1982, 1986) describes methods, as do Miller et al (2018), in their excellent manual on dune restoration. None of those reports mention the need for smoke treatment, a significant proposal of the Schmidt thesis (2006), which, when one reads the study, would seem to require much rigorous methodology to validate. (See my comments in Citations & Notes). Florida Rosemary Scrub is undervalued and thus under constant threat from development. (Kohfeldt, 2006)
Population Dynamics & Allelopathy: Many studies (particularly in the 1985-2008 period) have focused on documenting the mode of allelopahty, as well as the potential chemistry behind observed activity. Curiously, hardly any of those studies include photographs or drawings of the plants. But there have been areas of intense and devoted endeavor. A series of students working with Eric Menges at Archbold Biological Station (Venus, FL) have reported lab and field work on allelopathic interations, while a cohort of doctoral candidates working with Klaus Fischer at LSU have studied the chemistry of such interactions in Florida scrub species. A nice early summary of chemistry, though dated, can be found in Fischer, et al (1989). Most implications for allelopathy focus on the flavanoid Ceratiolin, which once leached from foliage and litter decomposes to Hydrocinnamic Acid, which is shown to have inhibitory affects on plants that were selected for testing (grasses) (Tanrisever, 1986). There are numerous implications from these many studies: A) Allelopathy impacts density, which may also result in some protection from fire, given this plant is an “obligate reseeder” that is usually killed by fire. B) Ceratiola longevity can be measured by counting terminal nodes (seasonal branching points), with many records suggesting that plants over 40 yr will be in decline. Plants remain juvenille for the first decade of life, with reproduction commencing by 15 years of age. C) Ceratiola is confirmed as dioecious, with most populations showing a 1:1 ration. Only one study, in just one of seven populations (Schmidt) suggested SSS (spatial segregation of sexes) might be demonstrated. D) Studies trend toward indicating Ceratiola success is fire-dependent. Schmidt (2006) states that recruitment is most reliable when the fire interval is around 20 years. This couples with claims that viability in the seed pool will not reach a decade, suggesting that more frequent fire, which clearly destroys these plants, could eliminate a population in that plants are non-reproductive (juvenille) for the first decade following germination.
CITATIONS & NOTES:
Bertoloni, Antoni (8 February 1775 – 17 April 1869) – Italian, Bertol. 1853. Miscellanea Botanica XIII, Memorie della Reale Accademia delle Scienze dell’Istituto di Bologna, Classe di Scienze Fisice From London Nat Hist Mus, available through BHL. (His son, Giuseppe Bertoloni, was also a botanist, with the standard abbreviation G. Bertol.)
In 1853 (50 years after Michaux’s publication of Ceratiola, Bertoloni described the new species, Empetrum aciculare, from a collection by Dr. Gates, in Alabama. The description is augmented with a nice illustration, unmistakably synonymous with Ceratiola ericoides.
Fischer, Nikolaus (Klaus) H. (1936 – present) – Germany (Univ. Tübingen), G. B. Williamson, N. Tanrisever, Ana de la Peña, J. D. Weidenhamer, Elizabeth D Jordan, and D. R. Richardson, 1989. Allelopathic Actions in the Florida Scrub Community, Biologia Plantarum (PRAHA) 31: 471-478. Abstract: “The hypothesis that allelochemicals released from members of the Florida scrub community deter the invasion of fire-prone sandhill grasses was investigated. Constituents of the endemic scrub members, Ceratiola ericoides, Conradina canescens and Calamintha ashei, were examined for their phytotoxic activity. Effects of the plant natural products on the germination and radicle growth of lettuce (Lactuca sativa), as well as little bluestem (Schizachyrium scoparium) and green sprangletop (Leptochloa dubia), two native grasses of the Florida sandhill community, were tested.
The data suggest that ursolic acid and other natural detergents which are released from a source plant enhance the solubilization of allelopathic lipids via micellization. In general, natural surfactants seem to play a significant role in the water transport of lipophilic phytotoxins to target seeds or seedlings.”
Some major points extracted verbatim from this summary: “The monotypic genus Ceratiola represents one of only three genera of the family Empetraceae. It is a locally dominant~endemic species of the Florida scrub community. Monthly bioassays have shown that water extracts of Ceratiola litter significantly inhibited germination and radicle growth of native grasses of the sandhillcommunitybut extractsof fresh leaves were only mildly active…water washes of freshly harvested leaves lacked the above phenolics but yielded a novel dihydrochalcone, ceratiolin.
Although ceratiolin at 125 ppm showed no inhibitory activity against S. scoparium and L.sativa, HCA exhibited considerable phytotoxic ettects. At concentrations at 123,250, and 500 ppm, HCA showed significant inhibitory activity on S. scoparium germination (46, 32 and 17 % of control)
Soil under C. ericoides is acidic, which promotes degradation of ceratiolin into HCA. Therefore, activity is likely to be greater in the sandy soil and decomposing litter than in fresh leaf rain washes.
Calamintha ashei is a member of the mint family (Labiatae), and an endemic of the Florida scrub. Water washes of fresh C. ashei leaves exhibited significant inhibitory activity on S. scoparium germination and growth.
Water washes of fresh Conradina canescens leaves were strongly inhibitory due to the presence of a series of monoterpenes. A bioassay-guided search for active con- stituents of C. canescens gave a highly active chromatographic fraction from the diethyl ether extract.
We were able to demonstrate that water leachates of Ceratiola ericoides, Calamintha ashei, and Conradina canescens form micelles. Since the leaf waxes of all three scrub species are rich in UA, this triterpene most likely provides the matrix for miceliization. These results suggested that UA (Ursolic Acid) acts as a micellar host, in particular for the bioactive terpenoids in’ C. ashei and C. canescens rain washes. This would enhance the rate of “solubilization” of plant lipids in aqueous foliar leachates and/or aid the transport to target seeds or plants. The “synergistic” allelopathic effect of UA, as demonstrated for Calamintha terpenoid constituents, is presently not understood.“
For more information on Fischer – See LSU Dept. Chemistry website: https://www.lsu.edu/science/chemistry/people/emeritus-pages/nikolaus-fischer.php His Ph.D. students from LSU: Donald L. Perry (1975); Huei-Nan Lin (1976); Gary P. Juneau (1977); June Walachy-Klimash (1980); Errol J. Olivier (1980); Ihl Young Lee (1983); Arcelio J. Malcolm (1983); Alfonso Gustavo Ober (1984); David Vargas (1985); Porfirio Caballero (1985); Nesrin Tanrisever (1986); Karla A. Wilzer (1986); Felix J. Parodi (1988); Marta Vasquez (1989); Elizabeth Douglas Jordan (1990); Marios A. Menelaou (1990); Howard G. Pentes (1991); Marco L. Gomez-Barrios (1991); Isabel Salkeld Núñez (1992); Tian-Sheng Lu (1994); Qi Song (1995); Heekyung Tak (1995); Joseph K. Rugutt (1996); Steven L. Robbs (1997); Charles L. Cantrell (1998)
Elisens, Wayne J. 2024 – Ceratiola, current page on Flora of North America website. http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=220002586
Gandoger, Jean Michel (10 May 1850 – 4 October 1926) – French. 1919. Sertum plantarum novarum, Pars secunda, Bulletin de la Société botanique de France, 66: 216-233. With a brief entry among new descriptions for plants from across the globe, Gandoger typified Certatiola falcatula based on Samuel Tracey’s collection #6782, reported from Palma Sola, FL, which would be near Bradenton (Manatee County). Gandoger also cites two Rolfs collections – Note: Peter Henry Rolfs is credited as founder of the University of Florida Herbarium (communication from Alan Franck). Gandoger (in the original article, spelled Gondoyer) defined his new species, now subsumed to Ceratiola ericoides, as having longer leaves than the Michaux plant.
A bit about Gandoger from Wikipedia: “Abbé Jean Michel Gandoger was a French botanist and mycologist.[1] He was born in Arnas, the son of a wealthy vineyard owner in the Beaujolais region. Although he took holy orders at the age of 26, he devoted his life to the study of botany, specializing in the genus Rosa. He travelled throughout the Mediterranean, notably Crete, Spain, Portugal, and Algeria, amassing a herbarium of over 800,000 specimens, now kept at the Jardin botanique de Lyon. However, he is notorious for having published thousands of plant species that are no longer accepted. He died at Arnas in 1926.”
Gibson D. J. and Eric S. Menges, 1994. Population structure and spatial pattern in the dioecious shrub, Ceratiola ericoides. J Veg Sci.. 5:337–346. https://www.jstor.org/stable/3235857, viewcontent.cgi
Hewitt, Rebecca E. & Eric S. Menges, 2008, Allelopathic effects of Ceratiola ericoidses (Empetraceae) on Germination and Survival of Six Florida Scrub Species, Plant Ecology 198: 47-59. The study published in 2008 follows up on Hunter and Menges (2002), testing germination of six different herbaceous species that are significant components of the South Florida Rosemary Scrub community, but show “varying degrees of habitat specialization” – Lechea deckertii, Palafoxia feayi, Polygonella robusta, Hypericum cumulicola, Lechea cernua, and Polygonella basiramia.
Though conducted in the field, these trials also involved watering seed with leachate generated by the researchers. Their work also included use of leachate from root tissue. Discussion concludes: “Field germination of six Florida scrub species was inhibited by Florida rosemary leachates. This is consistent with several lab and greenhouse studies which have shown that allelochemicals from Florida rosemary reduced germination of pyrogenic sandhill grasses …”
Hunter, Molly E. and EricS. Menges, 2002. Allelopathic effects and root distribution of Ceratiola ericoides (Empetraceae) on seven rosemary scrub species. The American Journal of Botany, 89: 1113-1118.
Johnson, A. F. 1982. Some demographic characteristics of the Florida Rosemary Ceratiola ericoides Michx. Am. Midl. Nat. 108: 170-174. https://www.jstor.org/stable/2425306
Johnson, A. F. 1986. “Recipe for growing Florida rosemary, Main Ingredient: Patience!” Palmetto Spring 5.
Johnson, A. F. and W.G. Abrahamson, 1990. A Note on the Fire Responses of Species in Rosemary Scrubs on the Southern Lake Wales Ridge. Florida Scientist, 53: 139-143.
Jordan, Elizabeth Douglas (4 April 1963-present) Georgia, USA., 1990. Determination of allelochemicals in the environment surrounding Ceratiola ericoides, Ph. D. Thesis, Louisian State University and Agricultural and Mechanical College. https://repository.lsu.edu/cgi/viewcontent.cgi?article=5924&context=gradschool_disstheses
The thesis begins Biblically, quoting Brahams, in German, with Google providing the translation: “For all flesh is as grass, and all the glory of man is as the flowers of grass. The grass has withered and the flower has fallen… But the word of the Lord remains forever.” Johannes Brahms, A German Requiem 1. Peter 1, 24 and 25.
Jordan defines her project:
- “Hydrocinnamic acid (HCA) is a decomposition product of the dihydrochalcone ceratiolin. Ceratiolin has been isolated from Ceratiola ericoides, a shrub endemic to the Florida scrub community (Tanrisever, et al., 1987). A bare zone surrounds mature C. ericoides shrubs, and previous investigations have indicated that allelochemicals contribute to this phenomenon (Richardson, 1988). HCA has been shown to inhibit germination and radicle growth of grasses common to the neighboring Florida sandhill community (Fischer, et al., 1988). The objective of this work was to determine the fate and recovery of HCA applied exogenously to scrub soil.“
- “It was the objective of the current study to monitor the release of ceratiolin and hydrocinnamic acid into the environment surrounding C ericoides shrubs. In addition, trans-cinnamic acid (TCA) and acetophenone (ACP) were determined. Conclusion. In summary, the results presented here provide evidence that a compound previously isolated from C. ericoides and its toxic decomposition product are released into the environment through leaching from leaves or litter. Further investigation of the toxicity of ACP and possible synergistic or additive effects of the compounds reported here is needed to more fully understand the observed allelopathic activity of C. ericoides.” The text, however, indicates levels from soaking plant litter are significantly higher than from misting.
- Although it has been reported (Tanrisever, 1986) that fresh C. ericoides leaves are odorless, DHSof leaves showed a large yield of volatile compounds. Many of these compounds have anti-germination activities (Reynolds, 1987; Bradow and Connick, 1988a; Bradow and Connick, 1988b; Reynolds, 1989); however, the role of these compounds as allelopathic agents cannot be assumed. Volatile compounds have strong activities as insect attractants or repellents (Visser, 1983; Williams, et al., 1988). Therefore, an investigation of the volatiles present in the litter and soil surrounding C. ericoides is part of our on-going research.
- Recently, the volatile compound composition of whole C. ericoides leaves has been reported. Identified from whole leaves were volatile esters, alcohols, and hydrocarbons in high abundance, and mono- and sesquiterpenes in low abundance (Jordan, Part I). The objective of the current study was to identify the major volatile compounds in soil and litter taken from beneath C. ericoides in the field.
Kohfeldt, Nancy, 2006. I Remember Rosemary, The Palmetto, Vol 23: 12, 13, & 15.
Michaux, André (8 March 1746 – 11 October 1802) – French. Noted for his 1803 Flora Boreali-Ameriana
Miller, D.L., M. Thetford, and M. Schneider. 2008. “Distance from the gulf influences survival and growth of three barrier island dune plants.” Journal of Coastal Research 24(3):261–266.
Miller, Debbie, Mark Thetford, Chrisina Verlinde, Gabriel Campbell, and Ashliynn Smith, 2018. Dune Restoration and Enhancement for the Florida Panhandle, UF/IFAS Extension Florida Sea Grant, University of Florida, PO Box 110409, Gainesville, FL 32611-0409, http://www.flseagrant.org. (available on-line).
Quintana-Ascencio, Pedro F.; Eric S. Menges, 1996. Inferring Metapopulation Dynamics from Patch-Level Incidence of Florida of Scrub Plants, Conservation Biology, Vol. 10, No. 4 (Aug., 1996), 1210-1219.
Schmidt, John Paul, 2006. Ph.D. thesis. Population Ecology of a Sandhill Endemic Shrub, Ceratiola ericoides (Sandhill Rosemary). University of Georgia, Athns.
For his thesis project at the UGA, Schmidt introduced the topic with a sweeping review of recent research, leading to 4 questions:
- “Does C. ericoides exhibit SSS (Spatial Segregation of Sexes); do males and females differ in growth, survivorship, age/size at reproductive maturity?
- Regarding Ceratiola ericoides demographics, how do fire and fire suppression affect rates of mortality, growth, and fecundity? Given the species is sensitive to fire, does not resprout following fire, and is slow to mature, what is an optimal fire frequency for C. ericoides?
- How should understanding the role of fire in the population dynamics of C. ericoides guide management of longleaf pine-turkey oak sandhills?”
After introducing the plant and describing basic biology, Schmidt identified his study sites in Georgia and South Carolina. in the “the Fall Line sandhills, a formation of remnant dunes which marked the Atlantic shoreline during the Miocene epoch.” As part of the study, Schmidt mapped and studied “1583 shrubs from 7 populations from 3 habitat variants.”
Addressing his first question, Schmidt concluded that in only one of 7 populations was there credible evidence that male and female plants survived in aggregated, non-random distribution patterns (SSS).
The remainder of his text basically addresses Schmidt’s three remaining questions through various studies. Reminding us “C. ericoides, a shrub that lives to 40+ years, which commonly occurs on sandhill sites, is not resistant to fire and, following fire, reestablishes only by seed“ Schmidt explains the plant is an “obligate reseeder”, which tells us that lacking the capacity to resprout after fire, populations are only restored through an existing seed pool. Using various model parameters, he compared “recruits” (successfully established seedlings) to expectations, both in fire and non-fire years. His definition of “juvenille” included plants with “4 or fewer nodes” – remembering that ecologists studying Ceratiola use the term “node” for what I’d call a super-node,, or terminal node, which is the major branching point terminate and defines each season’s growth.
As part of his work, Schmidt conducted a germination study, predicting that seed germinate more readily when activated by smoke, using methods described by Ann Johnson. He compared treated and non-treated cohorts of seed, the treated having been soaked in Liquid Smoke. Seventeen months later, Schmidt reports to have observed heavy germination in a treated flat, and no germination in the control. This is the weakest aspect of the study, in that Johnson described germination in about a year with scarification but no smoke treatment. I have a bottle of Liquid Smoke, which indicates the ingredients include natural mesquite smoke flavor, vinegar, molasses, and caramel for color. What is “natural mesquite smoke flavor”? How does vinegar impact results, (which to me are not perfectly rational)? How many seed were planted, how many flats? Did anyone inspect the flats on an on-going basis, or were open flats simply left in the nursery and checked 17 months later? Why did no seed germinate in the untreated flats? Since we are also told mice will eat and destroy the seed, did Liquid Smoke ward off predators? There’s every reason to expect there to have been some growth of untreated seed. I raise these questions not to be petty, but to challenge a concept that, though not rigorously tested, could make its way into popular and scientific lore. And it’s an important issue. If smoke truly stimulates germination, that becomes a crucial aspect of in understanding population dynamics, and establishes Ceratiola as fire-dependent. More pointedly, for this dissertation the issue of smoke synchronization for seed germination plays a significant role in conclusions, to wit: “Evidence from experiments I conducted suggests that C. ericoides seeds germinate in response to smoke as a trigger. The very large difference in fecundity between Fort Gordon and the other sites, therefore, reflects the effect of fire on seed germination. “ Reading the methods and results, I don’t agree this is well-supported.
Regarding field measurements, Schmidt’s conclusions confirm that “C. ericoides populations show much higher recruitment and mortality at the frequently burned site (Fort Gordon) than at either of the unburned sites. Whereas shrubs are associated with P. palustris on unburned sites, mortality risk is much higher near P. palustris when burning occurs. Maximum growth rates and reproductive output for C. ericoides occur when individuals are ~3 m in diameter (~15-20 years). Distance from nearest male is an important predictor of female fecundity. Seed banks may persist for more than 10 years.”
“The relationship between realized female fecundity and size—likelihood of recruits increases with size up to 3 m in diameter then declines–suggests that reproductive value of female shrubs > 3 m declines steadily with age. A diameter of 3 m corresponds to an average age of 18 years, when shrubs begin to senesce consistent with the life-history strategy of a fire-sensitive, woody species of the pyric sandhill community .“
“Recruitment likelihood also increases with proximity of female shrubs to males.”
”Results concur with estimates of seed bank longevity reported by researchers in Florida, who estimate that for inland populations of C. ericoides (which experienced stand-replacing fires historically unlike Florida coastal dune populations) most recruitment occurs within 10 years following a major fire. Smoke as an environmental trigger to germination synchronizes seedling emergence with post-fire conditions–a more open canopy and greater nutrient availability—thus optimizing seedling establishment.”
“At unburned sites where recruitment levels are low generally, seedling recruitment from persistent seed banks appears to be negligible. Even though the data suggest that persistent seed banks are present beneath dead females at unburned sites, apparently the absence of a strong environmental trigger to germination from smoke results in extremely low rates of germination as the viability of seeds within these seed banks decays over time.”
These observations generate answers to the 2nd, 3rd, and 4th questions Schmidt posed at the start. He concludes: “Fire increases seed germination probably because smoke is a trigger to germination:… an optimal fire return frequency is approximately 20 years;” and “the existence of C. ericoides populations on any sandhill site suggest that those sites (sic) experienced a fire frequency of 20 year or less… Given the patch nature of fire on longleaf pine-turkey oak sandhills, more frequent application of fire to those sites may be more effective in promoting species such as C. ericoides.” This, to me, exceeds what I would concluded from the data presented.
Tanrisever, Nesrin (22 February 1957 – present) – Turkey. 1986 Ph.D Thesis, Chemistry: Plant Germination and Growth Inhibitors from Ceratiola ericoides and Calamintha ashei. LSU. https://repository.lsu.edu/cgi/viewcontent.cgi?article=5210&context=gradschool_disstheses
Her introductory abstract nicely summarizes this work: “As part of a chemical-ecological study of the Florida scrub community, Ceratiola ericoides (Empetraceae) and Calamintha ashei (Lamiaceae) were chemically investigated for natural products with possible allelochemical activities.
The chromatographic separations and chemical investigations were guided by germination and radicle growth bioassays performed on seeds of commercial lettuce (Lactuca sativa) and Schizochyrium scoparium, a native grass of the Florida sandhill community.
From the dichloromethane extract of aerial parts of C. ericoides, 2′,4′-dihydroxychalcone, the dihydrochalcones angoletin and 2′,6′-dihydroxy-4-methoxy-3′,5′- dimethyldihydrochalcone, the flavanones 8- methylpinocembrin, 6,8-dimethylpinocembrin and 7- hydroxyflavanone were isolated along with the triterpenes erytrodiol and ursolic acid.
Significant inhibition on S. scopavium radicle growth was observed with 6,8-dimethylpinocembrin when applied in a saturated aqueous solution of ursolic acid.
From the active region of the ethyl acetate extract of C. ericoides, catechin, epicatechin, (A-2) dimer and related proanthocyanidins were isolated. Although mixtures of proanthocyanidins showed activity, A-2 alone exhibited no inhibitory effects on test seeds.
Surface washings of fresh C. ericoides leaves provided the novel dihydrochalcone ceratiolin. Ceratiolin decomposes spontaneously to form, besides other unidentified products, hydrocinnamic acid. Pure ceratiolin does not inhibit germination and radicle growth. However, hydrocinnamic acid shows significant inhibitory activity on both, L. eativa and S. scoparium.
From active chromatographic fractions of the dichloromethane extract of Calamintha ashei, two menthofurans, the known evodone and the new monoterpene calaminthone as well as the sesquiterpene caryophyllene oxide were isolated. The above terpene mixture completely inhibited S. eeopavium germination but bioassays performed with pure compounds exhibited no significant allelopathic activity. Volatility test of evodone showed strong inhibition on germination of S. scoparium seeds. A dramatic increase in inhibition of the radicle length of S. scoparium by evodone dissolved in a saturated aqueous solution of ursolic acid was observed when compared to a pure aqueous solution of evodone.
Tests for possible micelle formation, using the acridine fluorescence method with natural products and the surfactants ursolic acid and emulphogen indicated that mixtures of natural products in leaf leachates lead to micellar solutions which may aid the dissolution and therefore effectiveness of nonpolar allelochemicals.”
Thetford, M., D.L. Miller, and P. Penniman. 2001. “Vegetative propagation and production of Ceratiola ericoides Michx. for use in restoration.” Native Plants Journal 2(1):116–125.
Uphof, Johannes C.orneliusTheodorus, (1886-1969)- French. 1932. Quelques contributions à la connaissance de la famille des Empétracées (Ceratiola ericoides Michx), Bulletin de la Société Botanique de France, 1,2: 26-34.