GROWTH-RATE OF COTTON BOLLS AND THEIR COMPONENTS

The growth rate of cotton, Gossypium hirsutum L., bolls was investigated at three locations in the Coastal Plain of Israel. Random samples of bolls that had been tagged at anthesis were periodically taken. Burs and seed-cotton were weighed separately, after being dried, for each boll. The weight of the two heaviest bolls in each sample was taken as 'potential weight', and a temperature-dependent time-scale was used. It was found that the potential growth of whole cotton bolls may be modelled by using the following assumptions: (a) seed-cotton dry-weight follows a sigmoid function; (b) bur dry weight grows linearly during 21 days, with no further growth later on; (c) there is a maximum rate of boll growth with priority to seed-cotton, causing a decrease in bur dry weight during peak seed-cotton growth. Parameters for the cultivar Acala SJ-1 were calculated by fitting the functions to the observed data. Average boll weight was only 0.65-0.85 of the potential weight, probably because of stresses affecting whole plants or sites of individual bolls. © 1979.