Ghazi Mayla

Document Type

Dissertation - University Access Only

Award Date


Degree Name

Doctor of Philosophy (PhD)

Department / School



The term "allelopathy" refers to the effect, positive or negative, of a chemical (s) produced by one plant on itself or on another plant. These chemicals could be metabolic products excreted by the plants, or they could be residues of decaying plants which remain in the soil. In recent years, little work has been done on the role and importance of alkaloids in allelopathy. The object of this investigation is to study the effect of a group of closely related alkaloids in the Solanaceae family on the germination and radicle growth of lettuce seeds. Among the steroidal glycoalkaloids tested, chaconine had the most inhibitory effect on lettuce seed radicle growth followed by solanine, tomatine, solamargine and solasonine. Among the aglycones, solanidine produced fifty percent of the inhibitory effect on radicle growth. Solasodine and tomatidine had negligible effects. None of the above steroidal alkaloids had any inhibitory effect on the germination of lettuce seeds. The study showed that the sugar moieties of the glycoalkaloids played an important role in the inhibition of lettuce seed radicle growth and that the biological activity/toxicity of the steroidal alkaloids was in part due to the differences in their sugar moieties. The RhamnoseGlucose- Rhamnose sugar moiety, in its glycoalkaloid form, had about 2. 5 to 3 times greater inhibitory effect on radicle growth than the Glucose-Galactose-Rhamnose sugar moiety. The sugar moiety with the extra Rhamnose molecule is found to have the greater inhibitory effect.

Results from the histological study showed that the alkaloid treatments produced anatomical changes in the primary root. The changes were progressive, from the control to tomatine, solanine, and chaconine in the inhibition of cell enlargement of the ground meristem tissue of the root axis; in the increased darkening and necrosis of the outer ground meristem and protoderm; and in the increased lateral root initiation. These anatomical changes in the early stages of the primary root development were caused by the alkaloid treatments.

Library of Congress Subject Headings

Alkaloids -- Physiological effect Lettuce -- Seeds Allelochemicals



Number of Pages



South Dakota State University