ACCUMULATION OF FREE AMINO ACIDS AS A CHEMICAL BASIS FOR MORPHOLOGICAL SYMPTOMS IN TOBACCO MANIFESTING FRENCHING AND MINERAL DEFICIENCY SYMPTOMS

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Abstract
Frenching was accompanied by a marked increase in isoleucine and other free amino acids in the leaf lamina of field plants of Maryland Medium Broadleaf tobacco. The assumption that the rise in free amino acids in frenching was the primary cause or mechanism of symptom production in the plant was also supported by the analytical data on field plants showing mineral deficiencies. Sharp increases in free amino acids accompanied Ca, Mg, K and P deficiency, but not N deficiency. B and particularly S deficiencies were too slight to give definite chemical differences in tissues. It is probable that Ca, Mg, K, P and perhaps B function in amino acid and protein metabolism of the plant. Chloroses due to mineral deficiencies, excepting possibly Mg and N, are attributed primarily to the direct toxic action of excessive accumulations of metabolites.