Circadian ethylene production in cotton

Light strongly influences plant processes and is instrumental in establishing patterns in photosynthetic responses, enzymatic activity, and levels of some plant hormones. At this time, it is unclear how the biosynthesis of the plant hormone ethylene is influenced by light in cotton cotyledonary tissue. To answer this question, the cotton (Gossypium hirsutum L.) cultivar 'DPL50' was exposed to the following light and/or dark treatments over a 72-h period: a 12-h photoperiod, continuous light, or continuous dark. Ethylene, 1-aminocyclopropane-1-carboxylic acid (ACC), and N-malonyl-1-aminocyclopropane-1-carboxylic acid (MACC) were assayed from whole plant samples. Cotton plants exhibited a pattern of ethylene evolution that appears to be controlled by a circadian clock. This circadian pattern was suggested by the lack of change in ethylene evolution rate under continuous light. The pattern of ethylene evolution was disrupted during a continuous dark treatment, indicating that light in some way is responsible for setting the circadian clock for ethylene evolution and that light-sensing molecules such as phytochrome may be involved. Patterns of ACC and MACC concentration were not circadian.