چكيده لاتين :
Introduction
Thyme (Thymus vulgaris L.) is a perennial aromatic shrub belonging to the mint family (Davis, 1982) which has anti-spasmodic, antiseptic, carminative, anti-cough, sputum and antioxidant properties (Dapkevicius et al., 2002). Essential oil of thyme contains variable amounts of phenolic compounds such as thymol and carvacrol (20 to 80%), mono-terpinene hydrocarbons such as ?-cymene, ?-terpinene and alcohols such as linalool, ?-terpinene and tojan (Nickavar et al., 2005; Rustaiyan et al., 2000). Increasing the desired compounds of medicinal plants is possible by manipulation of cultivation techniques such as irrigation, fertilization or photo-bioreactor systems. Water deficiency is the most important factor limiting the growth and yield of drug crops, especially in arid and semi-arid regions (Babaee et al., 2010). Biofertilizers as an alternative in some cases and in most cases as a complement to chemical fertilizers can help to ensure the sustainability of agricultural production systems (Han et al., 2006). (Vital et al., 2002) mentioned the positive effects of biofertilizers in growth and yield of thyme.
The present study was designed to evaluate the effect of biofertilizers and drought stress on growth, yield and essential oil compounds of thyme.
Materials and methods
This experiment was conducted in a split-plot based on randomized complete block design with two replications, at the Research Farm of Zabol University, during the growing season of 2012 and 2013. The main plots consisted of irrigation with 30, 50, 70 and 90% of field capacity and subplots including plant inoculation with nitroxin, biophosphorus and mycorrhiza. Plant traits such as plant height (cm), fresh and dry weight of herbs (g.plant-1), essential oil percentage, essential oil yield (ml.plant-1) of thyme were measured. Chemical compositions of the oil were determined by gas chromatography (GC) and gas chromatography with mass spectrometer (GC/MS). For statistical analysis, analysis of variance (ANOVA), Duncan’s multiple range test (DMRT), simple correlation and stepwise regression were performed using SAS version 9.3 (SAS Institute Inc., Cary, NC, USA).
Results and discussion
In this experiment, the effects of drought stress, biofertilizer and their interactions with all studied traits were significant at the 1% probability level. The highest plant height (35.09 cm), fresh and dry weight of herbs per plant (103.52 and 43.27 g.plant-1, respectively.) and essential oil yield (0.350 mL.plant-1) belong to treatment of irrigation with 90% field capacity and nitroxin biofertilizer. The maximum essential oil percentage with 0.413% was obtained by irrigation with 70% field capacity and nitroxin biofertilizer. Fresh weight of herb per plant was the most crucial component in determining essential oil yield in thyme. Plants irrigated with 70% filed capacity gave the highest relative percentage of thymol, which reached 71.32, 50.68 and 47.71% in nitroxin, biophosphorus and mycorrhiza biofertilizer, respectively. This effect was accompanied with a decrease in ?-cymene content. Inoculation with nitroxin biofertilizer as compared to other fertilizers could further amend drought stress and improve the plant growth, essential oil percentage and yield and phenolic compound thymol of thyme. Thus, it appears that in order to achieve sustainable agriculture instead of chemical fertilizers, use of bio fertilizers is recommended.
References
Babaee, K., Amini Dehaghi, M., Modares Sanavi, S.A.M., and Jabbari, R. 2010. Water deficit effect on morphology, prolin content and thymol percentage of thyme (Thymus vulgaris L.). Iranian Journal of Medicinal and Aromatic Plants 26(2): 239-251. (In Persian with English Summary)
Han, H.S., and Lee, K.D. 2006. Effect of inoculation with phosphate and potassium co-insolubilizing bacteria on mineral uptake and growth of pepper and cucumber. Plant, Soil and Environment 52:130-136.
Davis, P.H. 1982. Flora of Turkey and the East Aegean Islands. University Press, Edinburgh 7: 320-354.
Dapkevicius, A., Van Beek, T.A., Lelyveld, G.P., Veldhuizen, A., Groot, A., Linssen J.P.H., and Venskutonis, R. 2002. Isolation and structure elucidation of radical scavengers from Thymus vulgaris leaves. Journal of Natural Production 65: 892-896.
Nickavar, B., Mojab, F., and Dolat Abadi, R. 2005. Analysis of the essential oils of two Thymus species from Iran. Food Chemistry 90(4): 609-611.
Rustaiyan, A., Masoudi, S., Monfared, A., Kamalinejad, M., Lajevardi, T., Sedaghat, S., and Yari, M. 2000. Volatile constituents of three Thymus species grown wild in Iran. Planta medica 66: 197-198.
Vital, W.M., Teixeira, N.T., Shigihara, R., and Dias, A.F.M. 2002. Organic manuring with pig biosolids with applications of foliar biofertilizers in the cultivation of Thyme (Thymus vulgaris L.). Ecossistema 27: 69-70.
