Ultra-structural and functional changes in the chloroplasts of detached barley leaves senescing under dark and light conditions.
Changes in the chloroplast ultra-structure and photochemical function were studied in detached barley (Hordeum vulgare L. cv. Akcent) leaf segments senescing in darkness or in continuous white light of moderate intensity (90 mumol m-2 s-1) for 5 days. A rate of senescence-induced chlorophyll degradation was similar in the dark- and light-senescing segments. The Chl a/b ratio was almost unchanged in the dark-senescing segments, whereas in the light-senescing segments an increase in this ratio was observed indicating a preferential degradation of light-harvesting complexes of photosystem II. A higher level of thylakoid disorganisation (especially of granal membranes) and a very high lipid peroxidation were observed in the light-senescing segments. In spite of these findings, both the maximal and actual photochemical quantum yields of the photosystem II were highly maintained in comparison with the dark-senescing segments.
Department of Experimental Physics, Palacký University, Tr. Svobody 26, 77146 Olomouc, Czech Republic. matousko@prfnw.upol.cz
Martina
M
Spundová
Hana
H
Popelková
Petr
P
Ilík
Jirí
J
Skotnica
Radko
R
Novotný
Jan
J
Naus
D002734:Chlorophyll / Q000378:metabolism; D000077194:Chlorophyll A; D002736:Chloroplasts / Q000378:metabolism* / Q000648:ultrastructure*; D003624:Darkness; D001467:Hordeum / Q000378:metabolism* / Q000528:radiation effects / Q000648:ultrastructure*; D008027:Light; D015227:Lipid Peroxidation; D008854:Microscopy, Electron; D045332:Photosystem II Protein Complex / Q000378:metabolism / Q000528:radiation effects; D018515:Plant Leaves / Q000378:metabolism / Q000528:radiation effects / Q000648:ultrastructure
D045332:Photosystem II Protein Complex; D002734:Chlorophyll; C037184:chlorophyll b; D000077194:Chlorophyll A