Figure 1.
Total mean amounts (±95% confidence interval) of volatile organic compounds (VOCs) emitted from P. aquilinum after various treatments: C, control (tap water); JA, jasmonic acid (1 mM); COR, coronalon (100 µM); ALA, alamethicin (10 µg ml−1); OPDA, 12-oxophytodienoic acid (1 mM); LA - linolenic acid (2 mM); MD, simple mechanical damage by pattern wheel; MW, mechanical damage by Mecworm; HG, damage by generalist herbivore (Spodoptera littoralis); HS, damage by specialist herbivore (Strongylogaster multifasciata).
The relative amounts of volatiles were determined as the ratio of peak area of a particular compound (AVOC) to the peak area of an internal standard (AIS) per gram weight of the dried frond. Different letters indicate significant difference between treatments (ANOVA: F9, 39 = 12.7, P = 0.01, LSD post hoc test: P<0.02, n = 3–6).
Figure 2.
Dose-dependency of the mean total VOC emission rates (±95% confidence interval) upon a application of different JA concentrations, post hoc and b increasing herbivore density.
The mean total VOC emission rates were determined as the mean of sum of all VOCs (determined as ratio of peak area of a particular compound (AVOC) to peak area of an internal standard (AIS) per gram weight of the dried frond) emitted after each treatment. Different letters indicate significant difference between the treatments (a univariate ANOVA on log-transformed data: F5, 11 = 65.5, P = 0.01, LSD post hoc test: P<0.01, n = 3, and b univariate ANOVA: F4, 19 = 0.7, P = 0.7, n = 4–6).
Figure 3.
Qualitative differences in the mean VOC emission rate (±95% confidence interval) after various treatments (same as in Fig. 1).
a Elicitor treatments (C, JA, OPDA, COR, LA and ALA) and b Damage treatments (C, MD, MW, HG and HS). The relative amounts of volatiles were determined as the ratio of peak area of a particular compound (AVOC) to peak area of an internal standard (AIS) per gram weight of the dried frond. Nine compounds were identified from the VOCs blends: 1: 1-octen-3-ol, 2:3-octanol, 3: p-cymene, 4: limonene, 5: γ-terpinene; 6: linalool; 7: nonanal; 8: α-terpineol; 9: (E)-β-farnesene.
Figure 4.
a Quantification and time course of mean JA and OPDA levels (±95% confidence interval) after simple mechanical wounding of three individual replicates per time point. b Quantification and time course of mean 13-HPOT concentrations (±95% confidence interval) after mechanical wounding of four replicates per time point. c Mean (±95% confidence interval) content of total esterified fatty acids before and 30 min after mechanical damage. Fatty acid content of three individual replicates is indicated as µg per gram fresh weight of the tissue.
Figure 5.
Quantification and time course of mean endogenous JA levels (±95% confidence interval) after wounding and treatment.
JA levels were quantified at different time points after mechanical wounding (Wounding + water), wounding + application of oral secretion (OS) collected from S. littoralis, and wounding + OS from S. multifasciata, both herbivores reared on fern diet. Data represents five individual replicates per time point and treatment.
Figure 6.
Mean VOC emission rate (±95% confidence interval) upon application of the inhibitors fosmidomycin (FOS) and mevinolin (MEV) prior to JA treatment.
VOCs emitted in response to treatments are grouped according to their chemical class (see Fig. 3a and 3b, C8 compounds (compounds 1–2; univariate ANOVA: F2, 13 = 6.6, P = 0.01, LSD post hoc test P<0.02; monoterpenes (compounds 3–7; univariate ANOVA: F2, 13 = 9.37, P = 0.03, LSD post hoc test P<0.03), and sesquiterpene (compound 9; univariate ANOVA on log-transformed data: F2, 13 = 10.7, P = 0.003, LSD post hoc test, P<0.05). Different letters indicate significant difference between the treatments.