Changes in the Pools of Carotenoids and Protochlorophyll(ide) in Etiolated Cucumber (Cucumis Sativus) Cotyledons Treated with Norflurazon and KC 6361 |
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Authors: | Jung S Kim JS Cho KY Kang BG |
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Institution: | (1) Dipartimento di Biologia, Universit? di Padova, Via U. Bassi 58/B, 35131 Padova, Italy;(2) Department Biologie I (Botanik), Universit?t M?nchen, Menzinger Str. 67, 80638 Munich, Germany; |
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Abstract: | Changes in the pools of carotenoids and protochlorophyll(ide) were investigated in etiolated cucumber cotyledons treated with
norflurazon (NF) and an experimental herbicide KC 6361 (KC). Both the NF- and the KC-treated tissues considerably accumulated
the colourless carotenes phytoene and phytofluene with a concomitant depletion of the coloured carotenoids lutein and β-carotene
in darkness. However, the profiles of changes in chlorophylls (Chls) and carotenoids were different for the two herbicides.
The plants were also influenced by the photosynthetic photon flux densities (PPFD's), with a more pronounced decline of Chl
under high PPFD than under low PPFD. The ratios of protochlorophyll (PChl)/protochlorophyllide (PChlide) were greatly altered
due to a decrease and an increase of PChl in the NF- and the KC-treated etiolated tissues, respectively, whereas the PChlide
content was not significantly influenced by the inhibitors. Large increase of PChls in the KC-treated tissues seems to derive
from the binding of accumulated geranylgeraniol (GG) equivalents, through carotenogenic inhibition, to PChlide. Therefore,
the alterations of PChl and PChlide occurring under disturbed carotenogenesis may suggest an interaction between the biosynthetic
pathways of Chls and carotenoids. In addition, the great proportion of PChl GG and PChl dihydro-GG in the KC-treated tissues
implies that PChl formation is regulated at the level of hydrogenation.
This revised version was published online in June 2006 with corrections to the Cover Date. |
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Keywords: | 5-aminolevulinic acid β -carotene carotenogenesis irradiance photosynthetic photon flux density phytol protochlorophyll xanthophylls |
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