Date of Award

5-1970

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Entomology

First Advisor

Sidney B. Hays

Second Advisor

A. E. Schwertz

Abstract

In South Carolina, the alfalfa weevil, Hypera postica (Gyllenhal), passed through a period of summer diapause or aestivation. This period was characterized by a gradual reduction of stored fat reserves and a decrease in respiration rate due to the loss of activity in the succinate oxidase system. These conditions persisted at a low level until the termination of aestivation, at which time they returned to pre-aestivation levels. Spectrophotometric estimates of isocitrate lyase activity indicated this system to be active following an initial period of aestivation and quickly decreased in activity with the termination of aestivation. On the basis of this observation, it was concluded that the isocitrate lyase system of the glyoxylate cycle served as a partial or main metabolic pathway during the period of adult aestivation. Tests for isocitrate lyase activity in the pupae of alfalfa weevils failed to indicate any activity. Experiments also were conducted to determine the effects of enzyme concentration and optimal pH for activity of isocitrate lyase in the alfalfa weevil. The enzyme concentration in the assay system was observed to produce Illaximum activity at a concentration greater than O, 1 O ml of homogenate. The optimal pH for the greatest amount of enzyme activity was observed to be 7. 2, and de creased under more acidic and alkaline conditions.

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