Nitrogen fertility effects on ethylene production in cotton

Abstract

Ethylene production is reportedly influenced by plant nutrient status. A field and two growth chamber studies were conducted to determine N fertility effects on ethylene production throughout development of cotton (Gossypium hirsutum L.) plants and plant parts. The association between changes in ethylene production due to N fertility and fruiting form abscission was also investigated. Nitrogen-deficient cotton plants exhibit increased rates of fruiting form abscission. Since ethylene is a potent promoter of abscission, it is implicated as a factor in this process. For all experiments, cotton plants were fertilized with NH4NO3 at planting at 0, 50, 100, or 150 kg N ha^-1. For the whole-plant study, ethylene production was measured using a flow-through system designed to collect ethylene from enclosed plants. Ethylene evolution from leaf discs of topmost fully expanded, middle, and bottom leaves of the canopy was determined in a growth chamber and a one-year field study. In addition, ethylene production from 3-d-old, 18-d-old, and 24-d-old squares, and 3-d-old bolls was sampled from field-grown plants. The whole-plant, growth chamber study was variable, but generally suggested ethylene production was increased for control plants. In addition, this response was unaffected by day temperature (28 or 35°C). Ethylene production of whole plants significantly decreased from 21 to 63 days after emergence (DAE). Ethylene evolution from leaf discs of the bottom leaves of the canopy of growth chamber-grown cotton plants was significantly increased for control plants at 14 DAE. However, from 21 to 42 DAE, ethylene production of those leaves increased with the amount of N applied. Older leaf tissue of field-grown cotton plants exhibited increased ethylene production with the amount of N applied, but only during the bloom period. Ethylene production by field-grown and growth chamber-grown plants increased with leaf age. Ethylene production by fruiting forms was not influenced by N fertilization, and abscission rates were not associated with ethylene production of fruiting forms, which suggested the fruit shed associated with a N deficiency might involve other hormones related to the abscission process.