期刊
JOURNAL OF PLANT PHYSIOLOGY
卷 161, 期 4, 页码 423-437出版社
ELSEVIER GMBH, URBAN & FISCHER VERLAG
DOI: 10.1078/0176-1617-01095
关键词
chloroplast structure; chlorophyll fluorescence; light-harvesting chlorophyll a/b protein complex; Mg deficiency; ozone; Picea abies (L.) Karst.; xanthophyll cycle; yellowing process
Biochemical, physiological and ultrastructural changes of the chloroplasts were examined in the course of the rapid yellowing process of spruce (Picea abies (L.) Karst.) at a Mg-deficient and ozone polluted mountain site (Schollkopf mountain, Central Black Forest, Germany, 840m a.s.l.). While at an early stage of yellowing the chlorophyll (Chl) content of the needles decreased slowly, significant changes occurred in the chloroplasts: The lability of the light-harvesting Chl alb protein complex LHC II increased; the thylakoid cross-sectional area of chloroplasts in the outer mesophyll of the needles decreased, and their Chl fluorescence showed typical changes like the decrease of Fv/Fm and the increase of the photoinhibitory Fv quenching. Later on, the Chl content decreased rapidly, the changes in the chloroplasts continued and the needles turned yellow. Lutein and the pigments of the xanthophyll cycle were enhanced in relation to Chl a. Light and dark reactions of the xanthophyll cycle were highly active indicating efficient proton pumping and NADPH formation. The ratio of non-appressed to appressed thylakoid membranes increased with decreasing Fv/Fm suggesting that structural and fluorescence properties of the chloroplasts were related. The response of the needles to defined shading and improved Mg supply was also examined. The combined effects of strong sun light, low levels of non-Chl-bound Mg (Mg-,Mg-free,Mg-) and ozone concentrations exceeding 80mug m(-3) are shown to be necessary to induce the rapid yellowing process. For needles with Mg,(free), <0.12 mg g(-1) needle dry matter, the lability of the LHC II was correlated with the ozone concentration suggesting that the destabilization of the LHC II plays a central role in the rapid yellowing process.
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