> My question is: what are the specific molecular effects of UV on the
> photosynthetic apparatus itself which may lead to decreased
> photosynthesis. It is known that DNA damage (and damage to other
> organells) will lead to decreased photosynthesis, but what about the
> photosynthetic machinery itself?
When you write "effects of UV" I suppose you want to say UV-B radiation
(290-320 nm) since UV-C is efficiently trapped by O2 in the atmosphere and
UV-A is not so harmful to biological tissues.
The most updated reviews I would suggest you are
1) Ultraviolet radiation, ozone depletion and marine photosynthesis.
Photosynthesis Research, 39:303-320 (1994).
2) Effects of UV-B radiation on photosynthesis and growth of terrestrial
plants. A. Teramura & J. Sullivan. Photosynthesis Research 39:463-473
(1994).
You can also see the book General Photobiology by D.P. Hader and M. Tevini,
and reviews from both authors; the first focuses his attention on the
effects on fitoplankton and marine algae, the second on the effects of UV-B
on terrestrial plants.
The main target of UV-B is not necessarily the DNA, although it's well
known that pyrimidine dimers and other damage may occur after exposure to
UV-B radiation. In that region of the spectrum also protein absorb
efficiently, chlorophylls may be excited too to produce dangerous radicals;
let's say, there are a few organic molecule that DON'T absorb that
radiation.
To answer your question about the damage to the photosynthetic machinery:
please read the following:
1)FEBS Letters 339 (1994): 217-221. Degradation of D2 protein due to
UV-B... by Friso et al.
2)BBA 1184(1994): 78-84. Degradation of Photosystem II reaction center D1
protein induced by UV-B..., by Friso et al.
