Relationship between Subtending Leaf Irradiance and Fruit Production and Quality of Cotton (Gossypium hirsutum L.)

Abstract

            Subtending leaf has been known to be a major source of photosynthate for the attached boll, but little is known about quantitative relationship between actual variability of subtending leaf irradiance and boll production and fiber quality. The objective of this study was to quantify this relationship by using low-cost photoelectric sensor mounted on subtending leaf surface for leaf irradiance measurement during 4 different periods of boll development, i.e. from squaring to 5 days after anthesis (DAA), from anthesis to 25 DAA (fiber elongation period), from 15 to 45 DAA (fiber thickening period), and from squaring to 45 DAA (Whole reproductive period), and the Advanced Fiber Information System (AFIS) for fiber quality analysis.

             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 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.