Relationship between subtending leaf irradiance and fruit production and quality of cotton (Gossypium hirsutum l.)

There were large variabilities of boll and boll component production, but less for fiber quality parameters, except short fiber content (SFC). Photosynthetically active radiation (PAR) captured by subtending leaves showed a substantial variation for each period of boll development whereas cumulative degree day (DD) was less variable. Variability of light captured by subtending leaf (LCS) was positively correlated with subtending leaf size. Increase in LCS during squaring-5 DAA resulted significantly in increased number of seeds and fibers per boll. During reproductive period (i.e. from squaring to 45 DAA), increasing LCS could increase significantly dry matter of the boll, seed cotton, carpel, delinted seed, and fiber. However, variability of LCS during fiber elongation period did not affect significantly fiber length (both mean length, L, and SFC). Fiber maturity and fineness, i.e. percentage of mature fiber (PM) and fiber linear mass (FIN), were not significantly affected by variability of LCS during 15-45 DAA. In this study, the DD during determining periods of boll-component development did not show significant influence on boll production and fiber quality. By hypothesizing that assimilates photosynthesized and stored in plant parts before the determining periods might also be used for fiber growth and development, fiber length (both L and SFC) showed a significant correlation with cumulative DD during squaring-25 DAA while fiber maturity and fineness (FIN) was significantly correlated with cumulative LCS during anthesis-45 DAA. Increasing light interception in the canopy may improve boll production and fiber quality of cotton. Quantitative relationship between subtending leaf irradiance and boll and fiber characteristics may be useful for developing predictive models of boll production and fiber quality in relation to light interception of cotton.