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

Thanisawanyangkura S., Sinoquet H., Clouvel P., Crétenet M., Jallas E.. 1997. Kasetsart Journal. Natural Sciences, 31 (5) : p. 128-142.

Subtending leaf has been known to be a major source of photosynthate for the attached bolI, but little is known about quantitative relationship between actual variability of subtending leaf irradiance and bolt 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 bolt 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 farce variabilities of boil and boil 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 bolt 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 bolt. During reproductive period (i.e. from squaring to 45 DAA), increasing LCS could increase significantly dry matter of the boil, 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 boil -component development did not show significant influence on boil 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 I-CS during anthesis-45 DAA. Increasing light interception in the canopy may improve boil production and fiber quality of cotton. Quantitative relationship between subtending leaf irradiance and boil and fiber characteristics may be useful for developing predictive models of boil production and fiber quality in relation to fight interception of' cotton.

Mots-clés : gossypium hirsutum; feuille; lumière; Énergie solaire; qualité; coton; fruit; radiation solaire; capsule

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