Flowering of cultivated varieties of cotton belonging toG. arboreum, G. herbaceun andG. hirsutum was delayed by over 14 hrs of daylength because of increase in number of days for square formation. The long day treatment in general increased height, production of fruiting branches, leaf area and dry weight per plant. The number of fruiting forms, bolls retained, yield of seed cotton and fruiting coefficient decreased under long day conditions. These characters were affected more in upland varieties and short day Cambodia derivatives. The most ofG. arboreum andG. herbaceum varieties became more vegetative in growth but their boll number and yield per plant increased.
Since the varieties 1998 F (G. hirsutum) and Gaorani 1111 (G. arboreum) were tolerant to long photoperiod and grew satisfactorily, it is suggested that these may be used as donor parents for improving the quality of cottons grown in northern India.