Quantification of Floral MeJA Emissions

The emission of MeJA was analyzed using headspace collection and GC-MS method, as described previously [38 (link)]. Briefly, the entire flower at each stage was enclosed in a 500-mL glass bottle with the addition of 1.728 μg of ethyl caprate as the internal standard. After the equilibrium of volatiles and internal standard for 30 min, an SPME fiber (Supelco, Bellefonte, PA, USA) was inserted into the bottle to trap volatile compounds for 30 min. Then, trapped floral volatiles were analyzed using a GC-MS system, as described above. The MeJA isoforms were identified by comparing the retention times and mass spectra with the authentic standard. Quantification was calculated based on the peak area ratio and the quantity of the internal standard using the Agilent ChemStation Data Analysis Application. Analysis of variance was carried out via SPSS 22 software using Tukey’s test (p = 0.05).