عنوان مقاله [English]
Thyme (Thymus vulgaris L.) is one of the most important essential oil plants that its essential oil constituent be used in different medicinal and food industries. Vermicompost is organic manure that significant amounts of macro and micronutrients make available to the plants. Although some of this material is minerals but most of them gradually and slowly released through the mineralization of organic matter. Mycorrhizal fungi are one of the biological factors in the rhizosphere, which include a relatively important part of soil organisms. Under water deficit conditions, mycorrhiza enhances photosynthesis and carbon fixation during the growing season by increasing the leaf area. This condition does not directly contribute to increased photosynthesis in the host plant, but keeps the photosynthesis level higher than control by improving water relations and changing the hormonal relations.
Materials and methods
The treatments included vermicompost in four levels (0, 2, 4, and 6 ton.ha-1) and mycorrhiza in three levels (without inoculation, inoculation with Glomus mosseae and Glomus intraradices) was arranged based on randomized complete block design with 12 treatments and 3 replications. Fresh leaf tissue was used to measure chlorophyll content. Dimethyl sulfoxide (7 ml) was added to 0.1 g leaf tissue and the samples were incubated at 70°Cfor 4h. The light absorptance was measured at 663, 645 and 470 nm with spectrophotometer (Jenway, 6305) to obtain chlorophyll content. To measure Arbuscular Mycorrhizal (AM) symbiosis, plant roots were collected one week before harvesting, cleaned by 10% KOH at 80˚C for 2h, and acidified in 1% HCL for 60 min. Then the cleaned up roots were stained in a solution of trypan blue. The roots were destained in a mixture of 500 ml glycerol, 450 ml water and 5 ml HCL for 24 h, allowing the fungus to be revealed under microscopic examination (Taylor et al. 2008).
Statistical analysis: Analysis of variance (ANOVA) was performed using SAS statistical software (SAS Institute, 1998) and Duncan's multiple range procedure was employed at probability level of 5%.
Results and discussion
The results indicated that the vermicompost application improved significantly plant height, dry weight, colonization, chlorophyll b, total chlorophyll, essential oil content, essential oil yield and thymol yield. Mycorrhizal inoculation affects significantly on chlorophyll b, total chlorophyll and colonization. The highest amount of plant height was recorded by application of 6 ton.ha-1 vermicompost (31 cm) and the lowest amount were obtained in control plots (21.78 cm).
The highest biological yield was obtained from application of 6 ton.ha-1 (3443 kg.ha-1) and the lowest biological yield was recorded in control plots (1966 kg.ha-1). Our results showed that colonization percent significantly increased by application of 6 ton.ha-1 in control plots (49.44 and 22.33%, respectively). The greatest amount of chlorophyll obtained by application of 6 tonha-1 vermicompost and the lowest amount was in control plots.
The best results of essence yield obtained from 4 ton.ha-1 vermicompost, while the maximum essence yield recorded by application of 6 ton.ha-1 vermicompost. The best interaction effects of vermicompost and mycorrhizal was significant on essential oil yield, thymol yield, chlorophyll b and total chlorophyll by the use of 6 ton.ha-1 vermicompost and without inoculation. The most content of chlorophyll a was obtained with the use of 4 ton.ha-1 vermicompost and inoculation with Glomus intraradices. The results showed the highest percent of colonization by the use of 6 ton.ha-1 vermicompost and inoculation with Glomus intraradices. The highest percent of essence was obtained from control (no application of vermicompost and no inoculation of mycorrhiza) treatment.
Vermicompost is one of the organic manure that significant amounts of macro and micronutrients make available to the plants. Mycorrhizal fungi are one of the biological factors in the rhizosphere that increased plant growth especially under stress conditions. In this study vermicompost application significantly increased essence yield. Also, vermicompost and mycorrhizal interaction increased chlorophyll content of plant leaf.