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

为探讨植物在机械损伤后C₆-C₁₀醛类化合物的释放机理, 及C₆-C₁₀醛类化合物对叶片光系统II (PSII)的影响, 以樟树(Cinnamomum camphora)为材料, 采用动态顶空气体循环法和热脱附/气相色谱/质谱联用技术(TDS-GC-MS), 对樟树幼苗叶片损伤后释放的C₆-C₁₀醛类化合物进行采集与分析, 并同步测定了脂氧合酶活性和损伤叶片的叶绿素荧光动力学参数。结果表明: 樟树幼苗叶片损伤后, 其挥发性有机化合物中己醛、庚醛、辛醛、壬醛和癸醛的释放量比损伤前分别增加了2.47、0.99、1.34、0.91和28.38倍(p < 0.01); 同时新增4种醛类化合物, 分别是: 2-己烯醛、2,4-己二烯醛、(E)-2-辛烯醛和(E)-2-壬烯醛。脂氧合酶活性比损伤前增加1.2倍(p < 0.01)。PSII单位反应中心复合体吸收的能量和被核心捕获的能量分别比损伤前下降12.8%和9.8% (p < 0.01)。单位面积反应中心的数量、电子传递量子产额、捕获激子能导致电子传递效率和叶片性能指数分别比损伤前增加23.3%、24.4%、22.6%和82.7% (p < 0.01)。损伤24 h后, 醛类化合物的种类、释放量、脂氧合酶活性及叶片叶绿素荧光动力学参数基本恢复到损伤前水平。说明机械损伤使PSII供体侧受损、脂氧合酶活性升高, 致使C₆-C₁₀醛类化合物大量释放, 樟树幼苗通过增加单位面积反应中心的数量来提高光合效率应对胁迫。

Effects of mechanical damage of leaves on volatile organic compounds and chlorophyll fluorescence parameters in seedlings of Cinnamomum camphora

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 (Q_A^–) 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.