Original scientific paper

Changes in Photosystem II Photochemistry in Senescing Maple Leaves

Hrvoje Lepeduš ; Agricultural Institute Osijek, Južno predgrađe 17, HR-31000 Osijek, Croatia
Vlatka Jurković ; Agricultural Institute Osijek, Južno predgrađe 17, HR-31000 Osijek, Croatia
Ivna Štolfa ; Department of Biology, University of J. J. Strossmayer in Osijek, Trg Lj. Gaja 6, HR-31000 Osijek, Croatia
Mirna Ćurković-Perica ; Department of Botany, Faculty of Science, University of Zagreb, Roosevelteov trg 6, HR-10000 Zagreb, Croatia
Hrvoje Fulgosi ; Ruđer Bošković Institute, Bijenička c. 54, HR-10000 Zagreb, Croatia
Vera Cesar ; Department of Biology, University of J. J. Strossmayer in Osijek, Trg Lj. Gaja 6, HR-31000 Osijek, Croatia

Abstract

Biochemical and functional changes in photosystem II (PSII) were investigated during natural
senescence of maple (Acer platanoides L.) leaves. Three different types of senescing leaves were used:
early senescent green (G), yellow green (YG) and yellow (Y). The main goal of this study was to investigate
the dynamics of degradation of major photosynthetic proteins (D1, LHCII and Rubisco LSU) and
how this would reflect on PSII photochemistry. It was revealed that D1 and LSU degrade faster than
LHCII. Such differential degradation dynamics influenced PSII photochemistry. A decrease in the maximum
(Fv/Fm) and effective (ΔF/F'm) quantum yields of PSII as well as a decrease in its capability for O2
evolution were observed. Analysis of chlorophyll a fluorescence transient measurement (OJIP test) in senescent
leaves showed striking decrease in performance index (PIABS), a measure of overall photosynthetic
performance. Further, increased absorption, trapping and dissipation of excitation energy per reaction centre
were found in senescent leaves. In addition, it was shown that a marked decrease in electron transport
beyond the primary electron acceptor (QA) in Y leaves was due to reduced electron transfer ability from
QA– to QB. It can be concluded that molecular and functional modifications of a certain fraction of reaction
centres from active to dissipative might be considered an important regulatory mechanism in chloroplast
electron-transport chain redox poise control during natural senescence of maple leaves.

Keywords

senescence; photosystem II; protein degradation; chlorophyll fluorescence

Hrčak ID:

62640

URI

https://hrcak.srce.hr/62640

Publication date:

1.12.2010.

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