Masters Theses

Date of Award

3-1969

Degree Type

Thesis

Degree Name

Master of Science

Major

Agronomy

Major Professor

Creighton L. Gupton

Committee Members

Laurence N. Skold, Horace C. Smith

Abstract

An experiment was carried out both in the field and in a greenhouse at the Tobacco Experiment Station, Greeneville, Tennessee, to determine the effect of root development on the concentration of nicotine in the leaves. In the field, plants of three genotypes were grown in Cumberland silt loam soil. Mature plant roots were dug and investigated by soil elution method. Root distribution, depth of penetration, and root yield were measured. Leaves and roots were dried and ground for nicotine analyses. Nicotine concentration was much lower for the roots in the soil of 0-30 centimeter depth than that for the roots distributed in the soil of 30-135 centimeter depth. Burley 49, which had a higher nicotine concentration in the leaves, was characterized by a greater ratio of fibrous root weight to the total weight of the root system and less tap root weight and lateral root weight or fewer number of lateral roots compared to the other two low alkaloid lines. These results suggested that nicotine is predominantly synthesized in the fibrous roots and is genetically controlled by each genotype. In the greenhouse, plants of three genotypes were grown in containers 35 centimeters in diameter and 60 centimeters in depth, which were filled with soil with three levels of compaction. Data were collected by the same method used in the field study. The extent of root growth for medium and heavy compactions were significantly greater than that for the light compaction. Total nicotine content in the leaves for the medium compaction was significantly higher than that for the other two compactions. Nicotine concentration in the leaves was not significantly affected by soil compaction. Correlation coefficients for the leaf yield and the root volume or root weight were positive and significant. Total nicotine content of the leaves was positively correlated with the root volume but only the correlation coefficient for the Burley 21 was statistically significant. Percentage nicotine in the leaves was not closely related to the extent of root growth.

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