P. Streb et al., RESISTANCE TO PHOTOINHIBITION OF PHOTOSYSTEM-II AND CATALASE AND ANTIOXIDATIVE PROTECTION IN HIGH-MOUNTAIN PLANTS, Plant, cell and environment, 20(8), 1997, pp. 1030-1040
In leaves of three alpine high mountain plants, Homogyne alpina, ranun
culus glacialis and Soldanella alpina, both photosystem II (PSII) and
the enzyme catalase appeared to be highly resistant to photoinactivati
on under natural field conditions, While the D1 protein of PSII and ca
talase have a rapid turnover in fight and require continuous new prote
in synthesis in non-adapted plants, little apparent photoinactivation
of PSII or catalase was induced in the alpine plants by translation in
hibitors or at low temperature, suggesting that turnover of the D1 pro
tein and catalase was slow in these leaves. In vitro PSII was rapidly
inactivated in light in isolated thylakoids from H. alpina and R. glac
ialis. In isolated intact chloroplasts from R. glacialis, photoinactiv
ation of PSII mas slower than in thylakoids. Partially purified catala
se from X. glacialis and S. alpina was as sensitive to photoinactivati
on in vitro as catalases from other sources, Catalase from H. alpina h
ad, however, a 10-fold higher stability in light, The levels of xantho
phyll cycle carotenoids, of the antioxidants ascorbate and glutathione
, and of the activities of catalase, superoxide dismutase and glutathi
one reductase were very high in S. alpina intermediate in H. alpina, b
ut very low in R. glacialis. However, isolated chloroplasts from all t
hree alpine species contained much higher concentrations of ascorbate
and glutathione than chloroplasts front lowland plants.