Canopy photosynthesis and fiber properties of normal- and late-planted cotton

Normal- and late-planted rotten (Gossypium hirsutum L.) often differ in fiber properties, especially those properties related to fiber secondary wall characteristics. This field study was conducted to (i) determine the effect of planting date on fiber properties of bells at two flowering times, and (ii) determine the relationship between fiber properties and canopy photosynthesis during development of those bells. Cotton ('Stoneville 453') was planted on 3 May and 3 June in 1995 and 3 May and 31 May in 1996. Canopy photosynthesis was measured 10 to 12 times on sunny days from initial flowering through the end of the season. Fiber properties were determined on first sympodial position bells that bloomed during the first and fourth week of flowering (WOF). Maximum canopy photosynthesis was 21% higher in 1996 than in 1995 and lint yield was 22% greater in 1996 than in 1995. Within each year, average maximum canopy photosynthesis did not differ between planting dates, although yield was approximately 30% lower for the late planting date each year. Bells from the first WOF generally had lower Lint percent, higher short fiber content, lower elongation, and lower whiteness index than bells from the fourth WOF. Micronaire, immature fiber fraction, and fiber cross-sectional area were linearly related to the amount of canopy photosynthesis that occurred from 15 to 45 d after flowering. Our results are consistent with the hypothesis that assimilate supply influences cotton fiber properties associated with secondary wall characteristics.