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not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
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site maintained by the Florida
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Copyright 2005, Board of Trustees, University
AGRICULTURAL RESEARCH & EDUCATION CENTER
IFAS, University of Florida
Bradenton, Florida /
Bradenton AREC Research Report GC1980-3 / March 1980i
EFFECTS OF FLUORIDES IN THE ENVIRONMENT UPON FLORIAN 31 i980
AGRICULTURE: RESEARCH AT AREC-BRADENTON*
S. S. Holtz and W. E. Waters
Compounds of the chemical element fluorine have variable and potent effects on
biological forms and therefore, agriculture. Fluorine, very electronegative and
extremely reactive, rarely is found in the elemental state in nature. Therefore,
most references are made to fluoride, the combined'form, rather than fluorine, the
elemental or pure state form. Fluoride has not been found to be essential to plant
life but is necessary to animals for bone and teeth formation. The chemical compound
Ca (PO ) 'CaF (apatite or fluor-apatite) is the form identified frequently in bones
ana teet Because of its insolubility and precipitation from seawater it has accu-
mulated as phosphate deposits in Florida. Fluoride is a by-product of phosphatic
fertilizer manufactured from Florida rock phosphates as well as a number of other
industries involving the burning and calcining processes that drive off fluoride,
as from aluminum ore processing.
The research at AREC-Bradenton has centered on the response of vegetable and
ornamental plants to fluorides in the environment, whether in air, soil, or water.
Research elsewhere indicates that cattle grazing on excessively-fluoride-contaminated
forage in Florida (above 30-40 ppm) would be injured by the high level of fluoride
intake if feeding were confined to such forage (7, 22). The first emphasis in
fluoride research at Bradenton was placed on gladiolus, an important commercial flower
crop. For a number of years, gladiolus plantings in Hillsborough and Manatee Counties
were affected with leaf injury of the tip-burn type named "leaf scorch.' Research
at AREC-Bradenton in 1952-53 (26) indicated that the cause of leaf scorch was airborne
fluoride. Other sources of fluoride were tentatively ruled out. High leaf fluoride
was associated repeatedly with greater leaf scorch which occurred at Ruskin and Sun
City, Florida compared with Fort Myers which appeared to be located out of the sphere
of influence of any significant amounts of airborne fluoride. Studies with gladiolus
have established this plant as an excellent indicator species for fluorides since it
is damaged by relatively low levels of the element.
A fundamental research program on the effects of fluorides upon plant metabolism
was conducted in 1961-64 under a major grant from the National Institutes of Health,
USPHS. The basic physiological processes that were studied in relation to fluorides
were photosynthetic efficiency, respiration rate, and the mechanism of translocation
and fate of fluoride accumulated by the plant (27-31).
Efforts were made to develop methods of controlling field damage by airborne
fluoride to gladiolus plants (24). The procedures developed were partially effective
but were not economically feasible. Soil-derived fluoride produced more internal-area
leaf scorch than air-derived fluoride (interior leaf area versus tip and margin) (29).
Prerequisites to soil-derived fluoride damage occurrence were 1) large superphosphate
applications, about 2 tons per acre,, and 2) low soil pH maintained by low-level lim-
ing (e.g., 0.5 ton dolomitic limestone per acre). Patterns of translocation of fluo-
ride compounds were studied in gladiolus leaves (30). Results indicated that soluble
fluoride is translocated passively with the transpirational stream of water traveling
through the leaf. Fluoride accumulated at tips and margins of leaves producing a
water-soaked area. initially dark green but later becoming tan or light brown. Arti-
ficial changes in transpiration stream by various methods of cutting notches and disks
out of leaves resulted in relocation of damage to new areas to which the transpira-
tional stream was forced to flow.
*Supported in part by the IFAS Center for Environmental Programs.
Citrus metabolism and yield was shown (28, 31) to be adversely affected by at-
mospheric fluorides, especially in terms of decreased photosynthesis and increased
wasteful respiration levels. De novo synthesis of chlorophyll necessary for photo-
synthesis was found to be a locus of significant plant damage and even more serious
was the loss of bloom set due to high episodes of atmospheric fluoride (3-6). Spe-
cific instances of fluoride damage to citrus were documented (1, 2, 7). Gladiolus
plants included with citrus in filtered and nonfiltered greenhouses were damaged in
19 days by ambient fluorides. Gladiolus plants placed outdoors also were damaged,]
but interestingly some plants placed in the path of the air exhaust from a filtered
greenhouse were protected by the constant atmosphere passing over them; once moved
out of the airstream, plants developed leaf scorch.
During the course of research with fluoride effects on gladiolus and citrus, the
faculty of the AREC-Bradenton and AREC-Lake Alfred have been called upon to assist
state regulatory agencies in establishing standards of fluoride content of plant
material indicative of the occurrence of air pollution damage. Hearings at Lakeland,
Ruskin and Sarasota resulted in the tentative or final setting of standards as fol-
lows: gladiolus 40 ppm, citrus 75 ppm on young leaves, and forage 45 ppm fluoride.
Experience has indicated these levels to be sufficiently elevated to preclude mis-
diagnosis. The standards have been on-and-off-again over the years according to
public interest and policy in environmental emphasis.
Fluorides contained in well water, fluoridated water supplies, and fertilizers
were found to be potential sources of difficulty in ornamental horticulture under
certain conditions (8, 9, 10, 21, 23, 24, 25). Well water containing 3.7 ppm fluor-
ide was found to be damaging when used as vase water for gladiolus, gerbera daisy,
poinsettia and rose (31, 32). More sensitive flowers such as gladiolus were also
damaged by concentrations as low as 0.5 or 0.25 ppm fluoride. Easter lily scorch,
a horticultural problem of long standing, was determined to be caused by soilborne
fluoride derived from phosphate fertilizer, the disorder was aggravated by high soil
acidity as well as well as high levels of ammonium and sodium ions. Methods were
outlined for the avoidance of leaf scorch of Easter lily (11-19, 33, 34).
Methodology was developed for comparative fumigation with hydrofluorice acid
(HF) of full-size plants. Compartmentalized fiberglass-wood-concrete greenhouses
were used in comparing the responses of large numbers of landscape, flowering and
foliage plants (35-40). Standardized, monitored levels of fluoride were maintained
for a 3-week evaluation of plant material. The comparative susceptibility was deter-
mined and symptomology carefully described. Photographic records were maintained.
Methods of plant, water and soil analysis have been developed from recent tech-
nology and literature for use in diagnostic and research procedures for field, green-
house, and homeowner plant material. Water samples and soil solution extracts are
analyzed directly with an Orion 901 lonalyzer fluoride ion electrode using compen-
sating buffers to essentially prevent completing of the fluoride ion and interference
by varied salt levels (33, 34). Plant material is ashed using calcium format, or in
some cases calcium hydroxide to trap fluoride. Fluoride-containing ash is then dis-
solved with hydrochloric acid, compensating buffer is added and fluoride is deter-
mined with the specific ion electrode. A small volume of an appropriate absolute
amount of fluoride is then added (20), and the percentage fluoride ion activity is
determined for each ash solution. The fluoride content is then calculated from the
initial fluoride activity reading adjusted for the percentage activity found under
the effects of the specific ionic composition of the sample as revealed by the known
addition technique. The procedure is reliable and very useful in diagnostic pro-
1. Cross, F. L., Jr. and R. W. Ross. 1969. Fluoride emissions from phosphate
processing plants. Fluoride 2(2):97-105.
2. Cross, F. L., Jr. and R. U. Ross.
due to a gypsum pond dyke break.
3. Leonard, C. D. and
cia orange yields.
1970. High fluoride levels in a citrus grove
H. B. Graves. 1966. Effect of airborne fluorides on Valen-
Proc. Fla. State Hort. Soc. 79:79-86.
4. Leonard, C. D. and H. B. Graves. 1979. Effect of fluoride air pollution on
Florida citrus. Proc. First Int'l. Citrus Symposium 2:717-727.
5. Leonard, C. D. and H. B. Graves, Jr. 1970.
on growth and yield of six citrus varieties.
Some effects of airborne fluorine
Proc. Fla. State Hort. Soc. 83:
6. Leonard, C. D. and H. B. Graves, Jr. 1972. The effect of fluorine level in
Valencia orange leaves on yield and fruit quality. Proc. Fla. State Hort. Soc.
7. Manatee County Health Dept., Environmental Engineering Division. 1977. Public
record files on gypsum pond environmental monitoring in North Flanatee County.
8. Marousky, F. J. and S. S. Woltz.
tive on quality of cut gladiolus.
1971. Effect of fluoride and flower preserva-
Proc. Fla. State Hort. Soc. 84:375-380.
9. Marousky, F. J. and S. S. Woltz. 1973. Relationship of floral preservatives
to water movement, fluoride distribution and injury in gladiolus and other cut
flowers. Acta Hort. (Proc. Int. Soc. for Hort. Sci.) 3: (Reference incomplete)
10. Marousky, F. J. and S. S. Woltz. 1974.
to water movement fluoride distribution
flowers. Acta Hort. 4:171-182.
Relationship of floral preservatives
and injury in gladiolus and other cut
11. Marousky, F. J. and S. S. Woltz.
lilies as influenced by fluoride
1975. Incidence of
leaf scorch in hybrid
Proc. Fla. State Hort.
12. Marousky, F. J. and S. S. Woltz. 1975.
hybrid lilies as influenced by fluoride
13. Marousky, F. J. and S. S. Woltz. 1975.
and soil pH to incidence of leaf scorch
Incidence of leaf scorch in Mid-Century
and superphosphate. Fla. Flower Grower
Relationship of phosphate fertilization
and fluorine content in Easter lilies.
14. Marousky. F. J. and S. S. Woltz. 1976. Incidence of leaf scorch in hybrid lil-
ies as influenced by fluoride and superphosohate. Fla. Flower Grower 13:1-6.
15. Marousky, F. J. and S. S.
Easter and hybrid lilies.
Inc. No. 29:52-56.
Woltz. 1976. Cause and control of leaf scorch in
The Lily Yearbook of the North American Lily Soc.,
16. Marousky, F. J. and S. S. Woltz. 1976. Influence of fluoride on leaf scorch
in various cultivars of Easter lily. HortScience 11:309.
17. Marousky, F. J. and S. S. Woltz. 1977. Influence of lime, nitrogen, and phos-
phorus sources on the availability and relationship of soil fluoride to leaf
scorch in Lilium longiflorum Thunb. J. Amer. Soc. Hort. Sci. 102:799-804.
18. Marousky, F. J. and S. S. Woltz. 1978. Soil fluoride availability as influ-
enced by pH calcium and superphosphate. HortScience 13:63. (Abstr.).
19. Marousky, F. J. and S. S. Woltz. 1978. Leaf scorch in Asiatic hybrid lilies.
Proc. Fla. State Hort. Soc. 91:201-204.
20. Melton, J. R., W. L. Hoover and J. L. Ayers. 1974. Known addition procedures
for determining fluoride in feeds with an ion-specific electrode. J. Asso.
Official Agr. Chem. 57:508-510.
21. Poole, R. T. and C. A. Conover. 1973. Fluoride-induced necrosis of Cordyline
terminalis as influenced by medium and pH. J. Amer. Soc. Hort. Sci. 98:447-448.
22. Suttie, J. W. 1977. Effects of fluorides on livestock. J. Occupational
23. Waters, W. E. 1966. Toxicity of certain Florida waters to cut flowers.
Proc. Fla. State Hort. Soc. 79:456-459.
24. Waters, U. E. 1968. Relationship of water salinity and fluorides to keeping
quality of chrysanthemum and gladiolus cut flowers. Proc. Amer. Soc. Hort.
25. Waters, W. E. 1968. Influence of well water salinity and fluorides on keeping
quality of Tropicana roses. Proc. Fla. State Hort. Soc. 81:355-359.
26. Woltz, S. S., R. 0. Mlagie, and C. M. Geraldson. 1953. Studies on leaf scorch
of gladiolus. Proc. Fla. State Hort. Soc. 66:306-309.
27. Woltz, S. S. 1962. Fluoride toxicity in gladiolus and methods of amelioration.
Proc. Fla. State Hort. Soc. 75:469-471.
28. Woltz S. S. and C. D. Leonard. 1964. Effect of atmospheric fluorides upon
certain metabolic processes in Valencia orange leaves. Proc. Fla. State Hort.
29. Woltz. S. S. 1964. Distinctive effects of root versus leaf acquired fluorides.
Proc. Fla. State Hort. Soc. 77:516 517.
30. Woltz, S. S. 1964. Translocation and metabolic effects of fluorides in gladio-
lus leaves. Proc. Fla. State Hort. Soc. 77:511-515.
31. Woltz, S. S., -U. E. Waters, and C. D. Leonard. 1971. Effects of fluorides on
metabolism and visible injury in cut flower crops and citrus. Fluoride 4:30-36.
32. Woltz, S. S. and F. J. Marousky. 1972. Effect of fluoride and a floral preser-
vative on fluoride content and injury to gladiolus florets and injury to poin-
settia bracts. Proc. Fla. State Hort. Soc. 85:416-418.
33. Woltz, S. S. and F. J. Marousky. 1975. Fluoride leaf scorch of lily and glad-
iclus: soil acidity, superphosphate and diagnostic techniques. Proc. Fla. State
Hort. Soc. 88:609-612.
34. Woltz, S. S. and F. J. Marousky. 1975. Fluoride toxicity as a factor in the
soil acidity complex affecting Easter lily and gladiolus. Fla. Flower Grower
v35. Woltz. S. S. and W. E. Waters. 1976. Response of some ornamental plants to
HF fumigation. HortScience 11:296.
36. Woltz, S. S. and W. E. Waters. 1976. Response of some ornamentals to HF
fumigation. Proc. Southern Nurserymen's Asso. Res. Conference 21st Ann. Rpt..
37. Woltz, S. S. and W. E. Waters. 1976. Susceptibility of some ornamentals to
fluoride air pollution. Bradenton AREC Res. Rept. GC1976-17.
38. Woltz, S. S. and W. E. Waters. 1977. Susceptibility of some foliage plants
to fluoride air pollution. Fla. Foliage Grower 14:5-7.
39. Woltz, S. S. and H. E. Waters. 1978. Airborne fluoride effects on some
flowering and landscape plants. HortScience 13:430-432.
40. Woltz, S. S. and W. E. Waters. 1978. Airborne fluoride effects on some foliage
plants. HortScience 13:585-586.