Experiments were conducted to examine the effects of PIX (n,n dimethypiperidinium chloride) on the cotton (Gossypium hirsutum L.) plants' growth, development and photosynthesis and its interaction with temperature. During the experiment the cotton plants were extensively mapped. All the flowers were tagged to obtain data on flowering, and boll opening. The number of days from flowering to boll opening were calculated for each open boll. The PIX treated plants took slightly more time for boll opening, and this difference between treated and untreated plants was statistically significant at the two lower temperatures. This difference, however, was probably due to the scattering of the data. It was also noted that the time from flower to boll opening decreased from the lower to the higher fruiting branches and that this difference was significant. This held for all temperatures and for PIX treated as well as untreated plants.