Changes in the chlorophyll fluorescence characteristics of chloroplasts from intact pumpkin cotyledons, caused by organ excision and kinetin treatment |
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Authors: | LM Behera and NK Choudhury |
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Institution: | (1) Laboratory of Byophysics and Biochemistry, School of Life Sciences, Sambalpur University, Jyoti Vihar -, 768 019 Sambalpur, India |
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Abstract: | The chlorophyll (Chl) fluorescence emission as well as excitation and polarization characteristics of chloroplasts from intact
cotyledons were determined in pumpkin seedlings after removal of one cotyledon (co-cotyledon) or apical bud or primary root,
or after kinetin treatment of derooted seedlings. Qualitatively, the fluorescence emission and excitation spectra of chloroplasts
were similar. The fluorescence emission spectra showed a maximum at 685 (F685) and a hump at 735 nm (F735), whereas the excitation
spectra showed peaks at 439, 471, 485, and 676 nm. The fluorescence intensities at F685 and F735 differed in various groups
of seedlings, as indicated by changes in their ratios. Similarly, the ratios of 471/439, 485/439, and 676/439 nm were also
different. Variability in the Chl fluorescence intensity values and the fluorescence polarization of chloroplasts prepared
from various seedling types may suggest a different degree of binding between the pigment complexes and light-harvesting Chl-protein
(LHCP), resulting in different rates of photoexcitation energy loss in the form of fluorescence emission. Kinetin treatment
improved the coupling of pigment complexes with reaction centre, as indicated by low polarization values in derooted and kinetin-treated
seedlings, which suggests the development of a suntype chloroplast.
This revised version was published online in June 2006 with corrections to the Cover Date. |
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Keywords: | apical bud cotyledon development Cucurbita maxima fluorescence absorption and emission spectra fluorescence polarization root |
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