Variation in Terpene Profiles of Thymus vulgaris in Water Deficit Stress Response

Abstract

Thyme (Thymus spp.) volatiles predominantly consisting of monoterpenes and sesquiterpenes, serve as antimicrobial, antiseptic and antioxidant in phytomedicine. They also play a key role in plants as secondary metabolites via their potential role against herbivores, attracting pollinators and abiotic stress tolerance. Plant volatiles are affected by different environmental factors including drought. Here, the effect of prolonged water deficit stress on volatile composition was studied on the sensitive and tolerant thyme plant cultivars (T. vulgaris Var. Wagner and T. vulgaris Var. Varico3, respectively). Volatile sampling along with morpho–physiological parameters such as soil moisture, water potential, shoot dry weight, photosynthetic rate and water content measurements were performed on one-month-old plants subsequent to water withholding at 4-day intervals until the plants wilted. The tolerant and sensitive plants had clearly different responses at physiological and volatile levels. The most stress-induced changes on the plants’ physiological traits occurred in the photosynthetic rates, where the tolerant plants maintained their photosynthesis similar to the control ones until the 8th day of the drought stress period. While the analysis of the volatile compounds (VOCs) of the sensitive thyme plants displayed the same pattern for almost all of them, in the tolerant plants, the comparison of the pattern of changes in the tolerant plants revealed that the changes could be classified into three separate groups. Our experimental and theoretical studies totally revealed that the most determinant compounds involved in drought stress adaptation included α-phellandrene, O-cymene, γ-terpinene and β-caryophyelene. Overall, it can be concluded that in the sensitive plants trade-off between growth and defense, the tolerant ones simultaneously activate their stress response mechanism and continue their growth.

Leaf Monoterpene Emission Limits Photosynthetic Downregulation under Heat Stress in Field-Grown Grapevine

“…Monoterpene emission has been previously shown to induce heat stress tolerance in several species [ 16 , 23 , 36 ]. For instance, Quercus ilex leaves fumigated with monoterpenes had a lower decline in photosynthesis compared to non-fumigated leaves when exposed to high temperatures [ 23 ].…”

Comparative Study of Drought Stress Effects on Traditional and Modern Apple Cultivars

“…Some plants accumulate osmolytes such as proline, glycine betaine and soluble sugars to protect themselves and to alleviate the drought stress condition [15][16][17]. Recent studies reported that some secondary metabolites synthesized in plant organs such as volatile compounds terpens [18] and some phytohormones such as brassinolide [19] alleviated the effect of drought stress on plants by improving the plant's defense system. The apple (Malus domestica Borkh.…”

Gentiana asclepiadea L. from Two High Mountainous Habitats: Inter- and Intrapopulation Variability Based on Species’ Phytochemistry

“…The high amount of these compounds in belowground organs, which is found in all ontogenetic stages for gentians [ 20 , 37 ], may imply a response to specific biotic pressures. However, more information regarding species autecology (i.e., photosynthesis, morphology, biotic interactions) would provide a better understanding of plant–environment relations among gentians [ 38 , 39 ].…”