Avena Coleoptile Assay of Ether Extracts of Aphids and Their Hosts

Abstract

1. Ether extracts of the aphids Hyalopterus arundinis, Aphis maidis, and Brevicoryne brassicae and of their respective hosts, Phragmites communis, Zea mays, and Brassica oleracea, consistently produced negative curvatures in the Avena coleoptile test. Extracts of the cabbage aphid and of the cabbage leaf were active in amazingly high dilutions. 2. Residues of equal samples of aphid and host extracts were not equally active. The extract of Hyalopterus arundinis was more active than the Phragmites leaf extract. The extract of the mealy cabbage aphid in higher concentrations was more active than the extract of the cabbage leaf; in lower concentrations this was not always the case. 3. Extracts of Hyalopterus arundinis and of Brevicoryne brassicae and of the hosts Phragmites communis and Brassica oleracea each contains a fraction which is active after acid, and another which is active after alkali, hydrolysis. 4. The results, especially in the tests with higher concentrations of extracts of cabbage aphid and cabbage leaf, are characterized by lack of proportionality between amount of sample extracted and activity of the residue of the ether extract in agar. 5. Distillates from the ether extracts of the cabbage leaf and cabbage aphid contain substances active in the coleoptile test. 6. Dry residues of the extracts of the cabbage aphid and leaf were active after six days' storage and also after thirteen days' storage in the dark at 0⚬ C., following a second solution in ether and evaporation to dryness. Better proportionalities between concentration and activity of the extracts were obtained when the extracts were not evaporated to dryness.