NITROGEN FERTILITY AND LEAF AGE EFFECTS ON ETHYLENE PRODUCTION OF COTTON IN A CONTROLLED ENVIRONMENT

The effect of nitrogen (N) fertility and its subsequent impact on ethy lene production varies with plant species. Additionally, ethylene prod uction reportedly increases or decreases with leaf age for several spe cies. We examined leaf age and N fertility effects on ethylene product ion of cotton (Gossypium hirsutum L.) during the early vegetative stag es of development (14 to 42 days after emergence) in a controlled envi ronment. Ethylene production was determined by sampling leaf discs fro m the topmost fully expanded, middle, and bottom leaves of the canopy at 14, 21, 28, 35, and 42 days after emergence. Ethylene was collected from leaf discs in sealed test tubes and quantified by gas chromatogr aphy. Early in development, a N deficiency was associated with elevate d levels of ethylene, suggesting stress ethylene production was occurr ing in response to a N-deficiency stress. As plant development progres sed, however, increased ethylene production was associated with higher levels of applied N. Additionally, higher ethylene production was lin early associated with higher chlorophyll levels in all three leaves sa mpled. Ethylene production within plants receiving any given rate of N initially increased and then decreased with leaf age. The dynamics of this relationship suggest that as the N status of the plant changes d uring plant development, the relative rate of ethylene production, wit h regard to leaf age, is significantly influenced.