CONTROLLED-TEMPERATURE EFFECTS ON COTTON YIELD AND FIBER PROPERTIES

Temperature effects on cotton yield and fibre properties of three cott on cultivars were determined. Plants were grown in pots maintained in growth rooms at varying day and night temperatures representing season ally constant or varying (C) or daily varying (V) regimes. Yield and f ibre characters responded to variation of daily mean and amplitude of temperature. Mean temperature reduction improved yield components, but fibre length, uniformity, strength and micronaire were increased by h igh, particularly high day, temperatures. A large daily temperature am plitude produced an intermediate number of flowers and the lowest rete ntion percentage. Fruiting and yield were increased by reduction in te mperature down to the threshold mean temperature of 22 degrees C. Howe ver, V-regimes with a low minimum temperature acted as a further drop (below 22 degrees C) of temperature and adversely affected these chara cters, An adverse effect of low minimum temperature combined with a mo derate day temperature was observed also on lint percentage and fibre properties. Varietal differences were more pronounced for highly herit able characters such as fibre properties, for which significant intera ctions between varieties and temperature also occurred. Differences in reproductive development were not sufficient to be of much practical importance.