Analysis of VOCs in the headspace of treated <i>G. biloba</i> leaves.

<p>Data are expressed as micrograms of VOCs per gram of leaf fresh weight (±SEM). Retention times (RT) and Kováts Index (KI) are indicated for each compound. For the same time point, boldface HW values indicate significant (P<0.05) differences between MD and HW. HW, herbivore wounding; MD, mechanical damage.</p

Gene expression of <i>G. biloba</i> leaves after 4 h from <i>S. littoralis</i> herbivory.

<p>Data are expressed as fold change by considering gene expression in mechanically damaged leaves equal to 1. Microarray data from the heterologous hybridization performed on Arabidopsis microarrays are listed along with qPCR data using <i>G. biloba</i> cDNAs. Genes are grouped by GO annotations. (±SD). Microarray Fold Change (FC).</p

Structure formulae of the main representative <i>G. biloba</i> compounds.

<p>Structure formulae of the main representative <i>G. biloba</i> compounds.</p

Time-course quantitative gene expression of some <i>G. biloba</i> genes involved in phenylpropanoid and terpenoid metabolism upon herbivory.

<p>Phenylalanine ammonia lyase (<i>PAL</i>) and anthocyanidin reductase (<i>ANR</i>) were significantly up regulated by herbivory only after 4 h, whereas flavonol synthase (<i>FLS</i>) was down-regulated at 30 min and 4 h. Chalcone synthase (<i>CHS</i>) showed a constant up-regulation, whereas flavanone 3-hydroxylase (F3H) showed an increased up regulation after 4 h. Farnesyl diphosphate synthase (<i>FPPS</i>) was significantly upregulated only after 30 min whereas geranylgeranyl diphosphate synthase (<i>GGPP</i>) showed no regulation at all times. Levopimaradiene synthase (<i>PPS</i>) was significantly down-regulated at all times. The dotted lines represent control values (mechanical damage), different letters indicate significant (P<0.05) differences, asterisks indicate significant (P<0.05) differences with respect to control.</p

Time-course quantitative gene expression of some ROS scavenging genes in <i>G. biloba</i> upon herbivory.

<p>Gene expression of superoxide dismutase (SOD) and catalase (CAT) was up-regulated by herbivory at all times. Upon herbivory, peroxidase (POX) was significantly down-regulated after 4 h, whereas ascorbate peroxidase (APX) was down-regualted after 30 min. The dotted lines represent control values (mechanical damage), different letters indicate significant (P<0.05) differences, asterisk indicates significant (P<0.05) differences with respect to control.</p

<i>G. biloba</i> is characterized by different leaf types, depending on the age and shape of the leaf.

<p><b>A</b>, bilobed; <b>B</b>, multi-dissected and; <b>C</b>, fan-shaped. Vm values are reported along with standard errors (in brackets) as mV (n≈50). Herbivore wounding is shown in leaf segments and Vm values are indicated below and aside the wounding zone. The leaf section of C shows Vm values of the different mesophyll and epidermal cells of a fan-shaped leaf. <b>D</b>, <i>Spodoptera littoralis</i> feeding on <i>G. biloba</i> leaves.</p

Subcellular localization of [Ca²⁺]_cyt and H₂O₂ in <i>G. biloba</i> leaves upon herbivory.

<p><b>A</b>. False color images from confocal laser scanning microscopy shows that upon herbivory [Ca²⁺]_cyt was found mainly in the cytosol, indicated by the calcium orange dye as green patches not associated with any specific organelle. Metric bar = 10 µm. <b>B</b>. H₂O₂ localization by Amplex Red shows a clear associations with microbodies (probably peroxisomes) and/or mitochondria but not with chloroplasts. Metric bar = 20 µm. In both panels, single arrows indicate the dye, double arrows indicate chloroplasts.</p

H₂O₂ variations in <i>G. biloba</i> upon mechanical damage and herbivore wounding.

<p><b>A</b>. Mechanically-wounded <i>G. biloba</i> leaves, values (n = 5) are expressed as µM H₂O₂ calculated from a calibration curve. The same letter indicates not significant (P>0.05) variation. B. Herbivore-wounded <i>G. biloba</i> leaves, values (n = 5) are expressed as µM H₂O₂. Different letters indicate significant (P<0.05) differences, the asterisk indicate significant (P<0.05) differences with respect to mechanical damage. In both panels, amplex indicates the absence of pharmacological agents.</p