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In order to study the effect of mycorrhizal fungi (inoculated and non-inoculated) and heavy metals stress [0, Pb (150 and 300 mg/kg) and Cd (40 and 80 mg/kg)] on pot marigold (Calendula officinalis L.), a factorial experiment was conducted based on a randomized complete block design with 4 replications in Research Greenhouse of Department of Horticultural Sciences, University of Tehran, Iran, during 2012-2013. Plant height, herbal and flower fresh and dry weight, root fresh and dry weight and root volume, colonization percentage, total petal extract, total petal flavonoids, root and shoot P and K uptakes, and Pb and Cd accumulations in root and shoot were measured. Results indicated that with increasing soil Pb and Cd concentration, growth and yield of pot marigold was reduced significantly; Cd had greater negative impacts than Pb. However, mycorrhizal fungi alleviated these impacts by improving plant growth and yield. Pot marigold concentrated high amounts of Pb and especially Cd in its roots and shoots; mycorrhizal plants had a greater accumulation of these metals, so that those under 80 mg/kg Cd soil(-1) accumulated 833.3 and 1585.8 mg Cd in their shoots and roots, respectively. In conclusion, mycorrhizal fungi can improve not only growth and yield of pot marigold in heavy metal stressed condition, but also phytoremediation performance by increasing heavy metals accumulation in the plant organs.

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In order to evaluate the possibilities of cultivation of Khorasan thyme (Thymus transcaspicus), an experiment was conducted in the years 2006 and 2007 under field conditions at the Research Station of the Faculty of Agriculture, Ferdowsi University of Mashhad, Iran. Irrigation and organic manure as organic fertilization were employed within a split-plot design with three replications. Irrigation intervals were imposed at three intervals of 2, 3 and 4 weeks, which were allocated to main plots and three levels of organic manure at 10, 20 and 30 t ha 71 were allocated to subplots. All other practices were based on organic manner cultivation. Plant biomass and its components as proportion of leaf, stem and flowers and also essential oil percentage and yield were measured at final harvest. Phenological cycles were recorded during the two years of the experiment. Results indicated that increasing application of organic manure beyond 10 t ha 71 did not show any significant effect on plant biomass. Increasing irrigation intervals in the second year of trial, significantly (p 5 0.05) reduced plant biomass. This was also true for stem, leaf and flower content in dry matter. Essential oil content and yield in response to organic manure and irrigation showed no particular trend. Phenological cycles were completed in 192 days equivalent to 3300 degree-days in the first year and 172 days equivalent to 3050 degree-days in the second year. The constituents of essential oil under field conditions were 25 components, which were 43.1% of the total essential content with thymol as the main constituent.

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In order to study the effects of biological and chemical fertilizers on quantitative and qualitative yields of purple coneflower, an experiment was carried out during 2010-2012. The morphological traits such as plant height, number of lateral shoots, shoot fresh and dry weight, root fresh and dry weight, number of inflorescences per plant, number of flower buds per plant, and essential oil content and yield were measured. The results showed significant effects of the treatments on the growth parameters. In the second year, the mixture of the three bacteria plus mycorrhizal inoculum improved important parameters such as shoot dry weight (40.42%), root dry weight (60.02%), and number of inflorescences per plant (65.68%). Interestingly, these values were not significantly different from obtained results by the chemical fertilizers. Additionally, the essential oil content in plants treated with the mixture of the three bacteria were 152.14% and 25.11% higher than the control plants in the first and the second year, respectively. The essential oil yield in plants treated with the mixture of the three bacteria was higher than those treated with the chemical fertilizers in two years. The results indicate that using biological fertilizers is a good choice to reduce the use of chemical fertilizers as an important tool to contribute to a sustainable agriculture.