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Title: EFFECT OF SOIL PH ON MINERAL ELEMENT CONCENTRATIONS OF TWO COCA SPECIES

Author
item Johnson, Emanuel
item Foy, Charles
item Campbell, Travis

Submitted to: Journal of Plant Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/6/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: The current research was conducted to determine the effect of soil acidity (pH) on mineral concentration of Ca, Mg, Fe, K, Al, Mn, Cu, and Zn in leaves, roots, and stems of two cultivated cocaine- producing species (Erythroxylum coca and Erythroxylum novogranatense). A naturally acidic (pH 4.7) Maryland soil was adjusted to provide 7 pH levels that ranged from 3.5 through 7.0. Optimal growth for E. coca occurred at pH 3.5 and for E. novogranatense, 4.7 through 6.0. At low soil pH, roots of both species accumulated high concentrations of Al which decreased as soil pH increased. The highest concentration of Ca was found in leaves of both species; however, E. coca accumulated more Ca as soil pH increased than did E. novogranatense. Mn and Zn concentrations in leaves decreased with increasing pH, where roots had higher concentrations than leaves; and Fe, Cu, K, and Mg concentrations showed erratic responses to increasing soil pH. Although the two species were tolerant of acid or neutral soils, they are distinctly different in tolerance to pH extremes. The results of the current study are of importance to plant and soil scientists conducting research on acid-loving plants, relationships between plant-soil interaction at low pH, the pharmaceutical industry, medicinal plant researchers, Drug Enforcement Agency, and CNC, because it showed how soil pH levels influenced mineral concentration and possibly the alkaloid content in the two cocaine- producing species.

Technical Abstract: In the current study, Erythroxylum coca var. coca Lam. (E. coca) and Erythroxylum novogranatense var. novogranatense (Morris) Hieron (E. novogranatense) were grown in greenhouse pots of Monmouth soil (clayed, mix mesic, typic Hapludult, original pH 4.7) over a pH range of 3.5 through 7.0, to determine the effect of soil pH (acidity) on mineral concentration of Ca, Mg, Fe, K, Al, Mn, Cu, P and Zn in leaves roots and stems of the two cultivated Erythroxylum species, from which cocaine is extracted. Optimal growth for E. coca occurred at pH 3.5 and for E. novogranatense, 4.7 through 6.0. At low soil pH, roots of both species accumulated high concentrations of Al which decreased as soil pH increased. The highest concentration of Ca was found in leaves of both species; however, E. coca accumulated more Ca as soil pH increased than did E. novogranatense. Mn and Zn concentrations in leaves decreased with increasing pH, where roots had higher concentrations than leaves; and Fe, Cu, K, Mg, and P concentration showed erratic responses to increasing soil pH. Although the two species were tolerant of acid or neutral soils, they are distinctly different in tolerance to pH extremes.