Volatile and Morphological Variation in Clinopodium macrostemum Explants Induced by Biotic and Abiotic Stress

The effect of different types of stress and elicitors on the morphological features and volatilome of Clinopodium macrostemum explants was studied. Ultraviolet (UV)-B light, pH (4 and 9), temperature (4 and 40°C), polyethylene glycol, and NaCl affected (p < 0.01-0.05) plant height, number of branches, foliar area, and number of leaves per explant. In contrast, UV-B radiation, alkaline pH, polyethylene glycol, and NaCl decreased glandular trichome density. Interestingly, UV-B light and chitin treatments triggered phenol accumulation and total antioxidant capacity in the plant model. The basal volatilome of C. macrostemum explants was analyzed by solid-phase microextraction/gas chromatography-mass spectrometry, revealing menthone and sabinene as major volatiles. Analysis of the C. macrostemum volatilome by principal component analysis and orthogonal partial least squares-discriminant analysis endorsed that 4°C, pH 4, pH 9, and glucanex treatments produced divergent volatilome sets, whereas treatments of UV-light, chitin, NaCl, and non-stressed plants produced a similar volatile profiling. Our study proposes specific volatiles linked to each stress assayed and demonstrates the plasticity of C. macrostemum volatilome, which could be considered to prevent odor quality losses in the plant.