title: Carotenoid composition in milo (Sorghum vulgare) shoots as affected by phytochrome and chlorophyll.
abstract: The composition of coloured carotenoids in the milo shoot was investigated quantitatively (high performance liquid chromatography) during light-mediated plastidogenesis, including the time span of 'photodelay' as caused by medium and high light fluxes. It was found that as long as only the far-red-absorbing form of phytochrome operates, the carotenoid pattern remains virtually the same as in complete darkness (violaxanthin and lutein as major constituents, traces of β-carotene). On the other hand, the pattern changes dramatically in white or red light with increasing amounts of chlorophyll (lutein and β-carotene dominate, β-carotene showing the strongest relative increase). Photodelay during the early phase of plastidogenesis affects the carotenoid composition strongly. Increase of neoxanthin, violaxanthin and β-carotene contents are diminished while lutein accumulation proves resistant towards chlorophyll-mediated photoinhibition. The photodelay can be diminished by an appropriate light pretreatment. The data indicate that light-mediated control over carotenoid accumulation is exerted at three levels: i) a coarse control through phytochrome, ii) fine tuning in connection with chlorophyll accumulation, iii) stabilization of holocomplexes against photodecomposition.
authors.affiliation: Biologisches Institut II der Universität, Schaenzlestraße 1, D-7800, Freiburg i.Br., Federal Republic of Germany.
authors.forename: R
authors.initials: R
authors.lastname: Oelmüller
authors.forename: H
authors.initials: H
authors.lastname: Mohr