On warm, still, sunny days, in the vicinity of plants
of Bf Bf constitution, a mild, pleasingly aromatic fragrance can be recognized.
Some persons detect it easily; some do not. I have been able to identify,
under good conditions (bright sunlight, still air), individual plants homozygous
for Bf Bf in segregating families, by the fragrance from a warm leaf surface
in the sun, and am satisfied that the judgment of full-grown plants by
a sensitive nose can be as reliable as ultraviolet fluorescence readings
in the seedling stage. From the sandbench, a bouquet of Bf Bf seedlings
displays a faint fragrance (again, if exposed to bright sunlight before
pulling). For classification purposes, homozygous and heterozygous constitutions
can be recognized as follows:
The combination of fluorescence and fragrance could be used in a laboratory seedling exercise (e.g., by separation for fluorescence, then comparing the fragrance between the separated seedlings - promptly). The fragrance is like that of bottle-on-the-shelf anthranilic acid, derivatives of which accumulate and cause the fluorescence in anthers of Bf/Bf and Bf/+ plants (H. J. Teas and E. G. Anderson, PNAS 37:645, 1951) due to a combination of changes in anthranilate synthetase activity levels, feedback response, and inhibition of one of the anthranilate-utilizing enzymes (M. Singh and J. M. Widholm, Biochem. Genet. 13:357,1975). While sunlight might contribute to stimulation of accumulation, enhancement of volatilization may be more likely.
E. H. Coe
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