Inhibitors of Plant Growth From the Leaves of Encelia farinosa

Author: Gray, Reed Alden

Year: 1948

Degree: Dissertation (Ph.D.)

Advisor: Bonner, James Frederick

Committee Member: Unknown, Unknown

Option: Biochemistry; Biology

DOI: 10.7907/109n-z614

Abstract

It has been shown that the leaves of Encelia farinose when applied to tomato and other plants in sand cultures cause a striking growth inhibition. Water and ether extracts of the leaves when fed to tomato seedlings in solution culture cause the death of the plants within one day. Fractionation of the leaf extracts yielded a crystalline compound which was isolated in pure form and is toxic to tomato seedlings in solution culture.

The structure determination and synthesis of this new compound, 3-acetyl-6-methoxybenzaldehyde (AMB), has been successfully worked out and is given in detail. The inhibitory activity of related compounds on the growth of tomato seedlings is demonstrated.

Another crystalline toxic compound has been isolated from leaves of Encelia farinose gathered in a different geographical location. Its toxic action is even more pronounced than that of AMB. This compound has been partly characterized and shown to be an aliphatic unsaturated lactone containing one hydroxyl group, three double bonds, and having a molecular formula of C16 H20 O4.

The presence of these growth inhibitors found in the leaves of Encelia farinose is offered as an explanation of why so few desert annuals are found growing in close relationship with the Encelia shrub on the desert.

Files