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Senescence and hyperspectral reflectance of cotton leaves exposed to ultraviolet‐B radiation and carbon dioxide
Author(s) -
Kakani Vijaya Gopal,
Reddy Kambham Raja,
Zhao Duli,
Gao Wei
Publication year - 2004
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.0031-9317.2004.00314.x
Subject(s) - photosynthesis , chlorophyll , carotenoid , carbon dioxide , stomatal conductance , chlorophyll b , botany , chlorophyll a , pigment , horticulture , chemistry , photosynthetic pigment , biology , organic chemistry
The objectives of this study were to determine the effects of UV‐B radiation and atmospheric carbon dioxide concentrations ([CO 2 ]) on leaf senescence of cotton by measuring leaf photosynthesis and chlorophyll content and to identify changes in leaf hyperspectral reflectance occurring due to senescence and UV‐B radiation. Plants were grown in controlled‐environment growth chambers at two [CO 2 ] (360 and 720 µmol mol −1 ) and three levels of UV‐B radiation (0, 7.7 and 15.1 kJ m −2 day −1 ). Photosynthesis, chlorophyll, carotenoids and phenolic compounds along with leaf hyperspectral reflectance were measured on three leaves aged 12, 21 and 30 days in each of the treatments. No interaction was detected between [CO 2 ] and UV‐B for any of the measured parameters. Significant interactions were observed between UV‐B and leaf age for photosynthesis and stomatal conductance. Elevated [CO 2 ] enhanced leaf photosynthesis by 32%. On exposure to 0, 7.7 and 15.1 kJ of UV‐B, the photosynthetic rates of 30‐day‐old leaves compared with 12‐day‐old leaves were reduced by 52, 76 and 86%, respectively. Chlorophyll pigments were not affected by leaf age at UV‐B radiation of 0 and 7.7 kJ, but UV‐B of 15.1 kJ reduced the chlorophylls by 20, 60 and 80% in 12, 21 and 30‐day‐old leaves, respectively. The hyperspectral reflectance between 726 and 1142 nm showed interaction for UV‐B radiation and leaf age. In cotton, leaf photosynthesis can be used as an indicator of leaf senescence, as it is more sensitive than photosynthetic pigments on exposure to UV‐B radiation. This study revealed that, cotton leaves senesced early on exposure to UV‐B radiation as indicated by leaf photosynthesis, and leaf hyperspectral reflectance can be used to detect changes caused by UV‐B and leaf ageing.