US EPA

6665039 

Journal Article 

The effect of fluorides on Milo maize (Sorghum sp.) 

Hitchcock, AE; Zimmerman, PW; Coe, RR 

1963 

22 

(4) 

175-206 

BCI:BCI19654600017716 

HF or fluosilicic acid (H2SiF6) was the volatile fluoride used. Snow Princess and Elizabeth the Queen gladiolus (Gladiolus sp.) were used as indicators to compare the known differential response of these 2 varieties to fluorides with the response of Milo maize. Chlorotic and necrotic markings, uptake of F, and the growth and yield of plants and seed heads varied considerably with the variety of Milo maize, cultural site, stage of plant development, and dosage of fluoride. Milo maize leaves exhibited the most chlorosis and necrosis, and accumulated the most F when the plants were fumigated after the elongation stage of development. The amount of chlorosis increased with the age of the leaf in varieties Martin's and Plainsman. Both F-containing compounds were taken up in about equal quantities by leaves of a given variety and induced about the same amount of chlorosis. The terminal half of leaves of Milo maize and 4-inch tips of gladiolus leaves accumulated more F than entire parts of plants above ground. After HF fumigation the amount of foliar chlorosis in Milo maize and tip burn in gladiolus increased more rapidly with increasing concentration of fluorides in the air than from prolonging the period of exposure when equivalent amounts of F were brought into contact with the plants. Detectable amounts of F were not translocated from tissue high in F into the leaves which developed after exposure of the plants to fluorides. Significant effects of HF on size of Milo maize plants or yield of seed heads were associated with fluoride dosages that caused noticeable to pronounced chlorosis, but not in the case of dosages causing mild chlorosis or none. The same held true for the relation between dosage of HF, relative length of leaf tip burn (>3 vs.<3 inches), and yield of tops or corms of gladiolus. Additions of sodium fluoride (NaF) solutions and a relatively insoluble fluoride dust of unknown exact composition, but similar to cryolite, to the soil surface had no significant effect oh growth of Milo maize at dosages which caused traces to slight amounts of chlorosis. NaF was slightly more effective than the fluoride dust. In contrast, the higher dose of NaF retarded growth and flowering of Snow Princess gladiolus, whereas the fluoride dust had no significant effect. NaF induced 25 times as much tip burn and uptake of F as fluoride dust. Gladiolus plants exposed to micronized natural Greenland cryolite (Na3AlF6) for 25 days had significantly more tip burn in variety Snow Princess than in Elizabeth the Queen. Regrowth shoots of Martin's and Hegari Milo maize failed to develop chlorosis or necrosis even though they accumulated a significant amount of F. || ABSTRACT AUTHORS: From auth. summ