Effects of mechanical damage of leaves on volatile organic compounds and chlorophyll fluorescence parameters in seedlings of Cinnamomum camphora
樟树幼苗机械损伤叶片对挥发性有机化合物及叶绿素荧光参数的影响

Aims Our objective was to reveal the mechanism of the effects of mechanical damage of leaves on emission of C6–C10 aldehydes and the variation of PSII in Cinnamomum camphora leaves. Methods We analyzed the composition and content of the C6–C10 aldehydes in seedlings of damaged C. camphora by the dynamic headspace air-circulation method and thermal desorption system/gas chromatography/mass spectrum (TDS-GC-MS), measured the activity of lipoxygenases (LOX) in leaves after mechanical damage, and investigated the effects of mechanical damage of leaves on chlorophyll a fluorescence parameters. Important findings Results showed that the emissions of hexanal, heptanal, octanal, nonanal and decanal were increased by 2.47, 0.99, 1.34, 0.91 and 28.38 (p < 0.01) times, respectively, and four kinds of C6–C10 aldehydes were induced: (E)-2-hexenal, (E, E)-2,4-hexadienal, (E)-2-octenal and (E)-2-nonenal. The activity of LOX was increased by 1.2 times. The absorption flux per PSII reaction center and trapping flux were significantly decreased by 12.8% (p < 0.05) and 11.1% (p < 0.01), respectively. The density of the active reaction centers per cross section, quantum yield of electron transport, electron transport chain further than primary quinone acceptor of PSII (QA–) and the performance of PSII activity were increased by 23.3%, 24.4%, 22.6% and 82.7% (p < 0.01), respectively. The species and emissions of C6–C10 aldehydes, activity of LOX and chlorophyll fluorescence parameters nearly recovered after 24 h. This suggested that the damage caused by mechanically damaged stress is more prominent at the donor side of PSII. The activity of LOX was increased, and as a result the emission of C6–C10 aldehydes increased. In response to high salt stress, C. camphora seedlings improve the quantity of the active reaction centers.