the bracken fern ( pteridium aquilinum )
DESCRIPTION
The Bracken Fern ( Pteridium aquilinum ). Toxic effects on surrounding organisms and environment. By: Peter Andriakos. General Information. Wide distribution Globally extensive Widest distribution of any fern genus Among most common plants on the planet. Locally intensive - PowerPoint PPT PresentationTRANSCRIPT
The Bracken Fern (Pteridium aquilinum)
Toxic effects on surrounding organisms and environment
By: Peter Andriakos
General Information
• Wide distribution Globally extensive Widest distribution of any fern genus Among most common plants on the planet
• Locally intensive Rapid invasion of de-forested areas Cover increasing at a global level Major problems in the UK, Scotland, Wales,
South America
General Info. (cont.)
• Persistence spreads via rhizome widespread underground rootstock forms expansive stands, dense thickets
• Resilience limited only by extreme cold, altitude observed growing in wide range of soil pH highly successful dispersal abilities
Human Bracken Fern Consumption
Bracken fiddleheads harvested
Many cultures throughout history• Maori (NZ)• herbal remedy, food
Eastern Asia (Japan, China, Korea)• staple vegetable
Still utilized today as a foodstuff
Toxic effects are now known• continues to be utilized
Non- Human Consumption
Animal consumption
Domestic Herbivores Restricted feed availability Will consume readily
Major problem Toxic effects on animals Indirect effects on humans
Toxic effects observed in all animal species known to consume Pteridium aquilinum
Cows consuming Pteridium aquilinum while grazing
Toxic and Carcinogenic Effects of Bracken Fern
Wide variety of toxic effects observed vary by species among other factors
Several known toxins isolated from Bracken several carcinogenic others mutagenic
Experimental determination of toxicity studies conducted with laboratory animals myriad of syndromes observed again, vary by species
Bracken carcinogens in the human diet(Mahmood Shahin, Barry L. Smith, Arungundrum S. Prakash)
An all encompassing article…
Bracken Fern issues seen in animals Human health risks
Primary carcinogenic principal Mode of carcinogenic action
Cancer model
Toxic syndromes in animals
Numerous acute, toxic syndromes observed induced thiamine deficiency acute hemorrhagic syndrome
Severity dependant on… species and age of animal quantity/quality of plant consumed consumption rate
Acute hemorrhagic syndrome
seen in ruminants degenerative change in more rapidly dividing cells
epithelial necrosis - larnyx, pharynx, small intestine
bone marrow aplasia -Platelet production ceases -“Hemorrhagic crisis” occurs -Leucopenia, thrombocytopenia, granulocytopenia
Death occurs in a matter of weeks
Chronic Toxic Syndromes
Chronic toxicity in animals also observed… Bright blindness
seen in sheep (ruminant) (Watson et al., 1965) retinal stenosis, atrophy (Watson et al.,1972)
Enzootic hematuria Tumors in the bladder mucosa hemorrhaging in bladder wall Pamukcu et al., 1967
Carcinomas upper digestive tract
Laboratory Animal Experimentation
Rats first report of carcinogenic potential (Evans, Mason. 1965)
Diets containing Bracken powder, fronds, rhizomes• Higher incidence of tumor formation vs. control • Fronds vs. rhizomes (Hirono et al.,1973)
Duration of exposure critical factor• Subjects fed 33% dried bracken (Hirono et al., 1970)• 4 months vs. 8 months
Mice feeding trials, dried bracken (Yasuda et al.,1974) rib anomalies, sternebrae fusion Tumor formation Carcinogenic effects of cow milk (Pamukcu et al., 1978)
Other experimental animals… Guinea Pigs Japanese Quail Egyptian Toads
Human Health RisksIndirect effects of animal consumption
milk obtained from bracken fed cattle leaching in to water supply aerial dispersion of spores
Esophageal carcinomas observed
Japan (Kamon et al., 1975)
Gastric cancer frequency
Wales (Galpin et al., 1990) Costa Rica (Villalobos-Salazar et al., 1989) Brazil (Marliere et al., 1995)
Toxic Compounds Numerous molecules isolated
Carcinogenic, mutagenic Quercetin mutagen Ptaquiloside (PT) 10 carcinogenic principle
Ptaquiloside moleculeQuercetin molecule
Ptaquiloside (PT)
• Principal carcinogen in Bracken• Norsesquiterpene glucoside
• Difficult to isolate • Carcinogenicity confirmed by Hirono et al. in 1984
• Various other experimental confirmations
PT Action Mechanism
Proposed scheme of PT reaction pathway
Carcinogenic basis of PT
Carcinogenesis initial DNA damage DNA alkylation (adenine, guanine)
Adenine
Guanine
DNA Structure
PT Cancer Model
Multistage model for bracken-induced carcinogenesis
Occurrence of the carcinogenic Bracken constituent ptaquiloside in fronds, topsoils, and organic soil layers
in Denmark(Rasmussen, Kroghsbo, Frisvad, Hansen)
relevance human uptake via watersheds
Investigate occurrence of PT in fronds, topsoil materials
Multivariate data analysis
Materials/Methods
20 populations chosen in Denmark 3 sub-sites at each location
Sample at end of growing season Soil + plant material Dried milled stored @ 40 C
Frond height and density measured
Map of Denmark, study sites indicated
Soil Horizons
http://www.dpi.vic.gov.au/CA25677D007DC87D/LUbyDesc/AG1060a/$File/AG1060a.gif
Soil Horizon Diagram
Focus was on topsoil layers
Horizons O and A1
Other measurements taken Soil pH Organic Carbon Content Bracken Biomass Precipitation level Light exposure Turnover rate
Partial Least Square Regression Analysis (PLSR)
Performed on all variables less PT content
Correlate parameters with PT content in fronds, horizons
PT analysis Fronds, litter, O/A horizons Extraction using de-ionized H20 “cleaning" of sample with a resin Conversion to pterosin B Liquid chromatograph utilized
Results
Ptaquiloside content
PT content in… Fronds 110 - 3800 [μg g-1 ], mean = 550 [μg g-1 ] O horizons 0.09 - 6.43 [μg g-1 ], mean = 0.39 [μg g-1 ] A horizons 0.011 – 0.713 [μg g-1 ], mean = 0.031 [μg g-1 ]
Results PLSR findings
(+) (-)Light exposure Frond height
Turnover Rate
Carbon Content
Fronds
(+) (-)
Precipitation Amt. of Litter
Turnover Rate
Stand Size
O horizons
(+) (-)
Soil pH Precipitation
Stand Size
Easting
A horizons
Conclusions
Definitive evidence that PT is found in topsoils beneath Bracken stands
Possibility that leaching does occur
High precipitation areas most susceptible to watershed contamination
Questions Raised
How concerned should a local human population be?
Should Bracken management be implemented?– Has been in some areas…
Do these strategies need to be re-evaluated for their efficacy?– Bracken cover is increasing rapidly…
Need to think about Bracken management in agriculture from an environmental point of view…