Search results for "Diatoxanthin"
showing 4 items of 4 documents
Electrochromic absorbance changes in the chlorophyll-c-containing alga Pleurochloris meiringensis (Xanthophyceae)
1994
Flash-induced absorbance changes were measured in the Chl-c-containing alga Pleurochloris meiringensis (Xanthophyceae) between 430 and 570 nm. In addition to the bands originating from redox changes of cytochromes, three major positive and tow negative transient bands were observed both 0.7 and 20 ms after the exciting flash. These transient bands peaking at 520, 480 and 451 nm and 497 and 465 nm, respectively, could be assigned to an almost homogeneous shift of the absorbance bands with maxima at 506, 473 and 444 nm, respectively. The shape of the absorbance transients elicited from PS I or PS II was identical, and the two photosystems contributed nearly equally to the absorbance changes. …
The importance of a highly active and DeltapH-regulated diatoxanthin epoxidase for the regulation of the PS II antenna function in diadinoxanthin cyc…
2005
The present study focuses on the regulation of diatoxanthin (Dtx) epoxidation in the diadinoxanthin (Ddx) cycle containing algae Phaeodactylum tricornutum, Thalassiosira pseudonana, Cyclotella meneghiniana and Prymnesium parvum and its significance for the control of the photosystem II (PS II) antenna function. Our data show that Dtx epoxidase can exhibit extremely high activities when algal cells are transferred from high light (HL) to low light (LL). Under HL conditions, Dtx epoxidation is strongly inhibited by the light-driven proton gradient. Uncoupling of the cells during HL illumination restores the high epoxidation rates observed during LL. In Ddx cycle containing algae, non-photoche…
Supplementary Ultraviolet-B Radiation Induces a Rapid Reversal of the Diadinoxanthin Cycle in the Strong Light-Exposed DiatomPhaeodactylum tricornutu…
2002
AbstractA treatment of the diatom Phaeodactylum tricornutum with high light (HL) in the visible range led to the conversion of diadinoxanthin (Dd) to diatoxanthin (Dt). In a following treatment with HL plus supplementary ultraviolet (UV)-B, the Dt was rapidly epoxidized to Dd. Photosynthesis of the cells was inhibited under HL + UV-B. This is accounted for by direct damage by UV-B and damage because of the UV-B-induced reversal of the Dd cycle and the associated loss of photoprotection. The reversal of the Dd cycle by UV-B was faster in the presence of dithiothreitol, an inhibitor of the Dd de-epoxidase. Our results imply that the reversal of the Dd cycle by HL + UV-B was caused by an incre…
Multiple Short Term Effects of UV-B Radiation on the Diatom Phaeodactylum Tricornutum
1998
Increases in UV-B irradiance lead to many specific damaging effects upon the plants including damage of the thylakoid membrane, partial inhibition of PS II, decrease of chloroplast ATPase activity, loss of enzyme activities in the calvin cycle and alterations in pigment synthesis (1). Under natural conditions enhanced UV-B light is always accompanied by high intensities of photosynthetic active radiation (PAR). Damaging effects due to photoinhibitory PAR and UV-B light which lead to several oxygen radical species (2) could be reduced by photoprotection mechanisms. One of these protection mechanisms is the xanthophyll cycle. In higher plants and green algae violaxanthin is converted to zeaxa…