title: Photosynthetic performance during leaf expansion in Malus micromalus probed by chlorophyll a fluorescence and modulated 820nm reflection.
abstract: The simultaneous measurements of prompt chlorophyll a fluorescence, delayed chlorophyll a fluorescence and modulated 820nm reflection allow collection and correlation of complementary information for the three domains of the photosynthetic electron transport chain - the PSII electron donor side, electron transport between PSII and PSI, and the PSI electron acceptor side. In this study, we used this approach to investigate photochemical activity during Malus micromalus leaf expansion. The results showed that as leaves expanded, the antenna size per reaction center for the two systems became smaller, and the energetic connectivity of PSII units decreased gradually. Meanwhile, the light trapping efficiency of PSII, electron transfer capacity at the donor side of PSII, exchange capacity of PQs at the QB site and the reoxidation capacity of PQH2 were all increased as leaves expanded. However, the capacity of PQH2 reoxidation increased at a slower rate than the exchange capacity of PQs at the QB site. In general, during leaf development, the photochemical activity of both PSII and PSI increased, although the increase in PSII activity was faster relative to PSI. The results from the three independent signals corroborate each other.
authors.affiliation: State Key Laboratory of Crop Stress Biology for Arid Areas, College of Horticulture, Northwest A&F University, Yangling, Shaanxi 712100, China.
authors.forename: Jin
authors.initials: J
authors.lastname: Gao
authors.affiliation: State Key Laboratory of Crop Stress Biology for Arid Areas, College of Horticulture, Northwest A&F University, Yangling, Shaanxi 712100, China. Electronic address: Lipm@nwsuaf.edu.cn.
authors.forename: Pengmin
authors.initials: P
authors.lastname: Li
authors.affiliation: State Key Laboratory of Crop Stress Biology for Arid Areas, College of Horticulture, Northwest A&F University, Yangling, Shaanxi 712100, China.
authors.forename: Fengwang
authors.initials: F
authors.lastname: Ma
authors.affiliation: Department of Biophysics and Radiobiology, Faculty of Biology, St. Kliment Ohridski University of Sofia, 8, Dragan Tzankov Boulevard, 1164 Sofia, Bulgaria.
authors.forename: Vasilij
authors.initials: V
authors.lastname: Goltsev
mesh_terms: D002734:Chlorophyll / Q000737:chemistry / Q000378:metabolism*; D000077194:Chlorophyll A; D007700:Kinetics; D027845:Malus / Q000378:metabolism*; D055668:Photochemical Processes; D010788:Photosynthesis; D018515:Plant Leaves / Q000378:metabolism*; D013050:Spectrometry, Fluorescence
chemical_list: D002734:Chlorophyll; D000077194:Chlorophyll A
keywords: Delayed fluorescence; Leaf expansion; Malus micromalus; Modulated 820nm reflection; Prompt fluorescence