Abstract
The relationship between the peroxidative IAA-oxidase system and in vivo synthesis of ethylene in cotton (Gossypium hirsutum L. var. Watson GL-7) was investigated by using treatments such as supra-optimal levels of manganese and exogenous applications of IAA and 2,4-D which are known to alter these activities in cotton tissue. The objectives of this study were a) to determine if supra-optimal levels of tissue manganese would alter in vivo ethylene synthesis, b) to investigate the possibility of a role for manganese enhanced ethylene synthesis in the induction of early flowering in cotton, and c) to clarify the relationship between peroxidase, IAA-oxidase, and in vivo ethylene synthesis. Direct stimulation of in vivo ethylene synthesis by supra-optimal levels of tissue manganese was not indicated by this study. A correlation was noted, however, between internal ethylene concentration and the development of manganese toxicity lesions. At the threshold level of tissue manganese which results in the development of severe manganese toxicity symptoms in cotton, an increase in ethylene synthesis was simultaneously observed. A similar correlation was noted between the development of manganese toxicity lesions and IAA-oxidase activity. Moreover, a direct relationship was observed between the severity of visible toxicity symptoms and both IAA-oxidase activity and internal ethylene concentration. Correlations were also noted between IAA-oxidase activity and peroxidase activity and between peroxidase activity and internal ethylene concentration at tissue manganese levels causing severe toxicity symptoms. This evidence appears to support the hypothesis that an enzyme system similar to the peroxidative IAA-oxidase system is functional in the in vivo synthesis of ethylene. However, the initial significant increase in ethylene concentration observed in this study preceded that of both IAA-oxidase activity and peroxidase activity. ...
Fowler, James Lowell (1971). A study of the peroxidative indoleacetic acid oxidase system and its relation to in vivo ethylene synthesis in cotton. Doctoral dissertation, Texas A&M University. Texas A&M University. Libraries. Available electronically from
https : / /hdl .handle .net /1969 .1 /DISSERTATIONS -171064.