5.3. Action spectrum of photoinhibition suggests that both Mn and Chl
function as photoreceptor(s) of photoinhibition
The action spectrum of photoinhibition in vivo
from a higher plant (Paper II, Fig. 1) shows general similarities with the earlier
in vitro spectra (Jones and Kok 1966; Renger et al.
1989; Jung and Kim 1990; Santabarbara et al. 2001a; Hakala et al. 2005; Ohnishi et al.
2005), suggesting that the same photoinhibition reactions occur in both conditions.
Accordingly, in Synechocystis sp. PCC 6803 cells
the photoinhibitory efficiency of 400-450
nm light is over twice as high as that of 600-650 nm light and intermediate wavelengths
(450-600 nm) are less efficient (Tyystjärvi et al. 2002).
Furthermore,
transcripts of the
psbA gene that codes for the D1 protein in
Synechocystis
sp. PCC 6803
decrease after transfer
of the cells from darkness to orange light and
increase when the cells are transferred from
darkness to blue-green light, suggesting that also the redox state of the photosynthetic
electron transfer chain regulates
psbA
transcription (El Bissati and Kirilovsky 2001). In
comparison with the
in vitro
action spectra, the
in vivo
spectrum is more flat in the visible
light region and shows higher sensitivity to UV light. This difference between
in vivo
and
in
vitro
action spectra may partially be caused by the fact that leaves are optically thicker than
thylakoid suspensions used
in vitro
. Furthermore, leaves show a variety of responses to
light quality and intensity that are absent in isolated systems (for review, see Demmig-
Adams and Adams 1992; Niyogi et al. 199
.
http://www.helsinki.fi/fdpps/PhD theses/Sarvikas.pdf
