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Drought stress is one of the growing concerns in agriculture management around the world. Adopting tolerant plants to drought conditions could be an appropriate approach to this problem. Bunium persicum is one of the most important medicinal plants of Iran and Turkey as well as neighbouring countries and has been forced into endangered plant status due to mismanagement of its wild habitats. An experiment was conducted in order to evaluate drought tolerance of Bunium persicum and the effects of drought on its essential oil qualitative properties. Two separate plans based on randomised complete block design were performed with 4 drought levels (irrigation after 60, 90, 120, and 150 mm of evaporation from an evaporation basin) and 3 replications. Drought treatments were applied after the stem elongation and flowering stages. Results indicated that applied drought treatments reduced yield and yield components of plants in both growth stages. Some differences were observed in yield components when plants were exposed to drought stress at different growth stages. The essential oil percentage of Bunium persicum was affected by drought conditions, and it was elevated along with increasing drought levels. Due to reduced seed yield, essential oil yield was significantly decreased. Antioxidative activity assessment of seed extracts revealed that drought had positive effects on antioxidant parameters, including 2′-diphenyl 1-picrylhydrazyl radical scavenging activity, hydrogen peroxide scavenging activity, and Fe-reducing power. Phenol content was also improved through applied drought treatments. In general, these results showed the high tolerance of Bunium persicum to drought and also revealed positive effects of drought on the antioxidative activities of plant seeds.

Zinc oxide-engineered nanoparticles (ZnO ENPs) have received the most attention in recent years. This increasing interest has been directed towards studying the environmental fate and effects of ZnO ENPs on ecological terrestrial species. In this study, ZnO NPs were synthesized by atmospheric pressure solution evaporation method and were coated or uncoated with humic acid (HA). The root uptakes of uncoated and HAcoated ZnO NPs and zinc (Zn) were investigated by gel-grown cucumber. Two ZnO levels (1 and 200 µM) were applied in the form of coated (T 3 ) and non-coated (T 2 ) NPs or bulk particles (T 1 ). The results showed that coating NPs by HA increases zeta potential of NPs and decreases their aggregation size due to the increase in the repulsion forces among the particles. Addition of 1 mgL −1 ZnO into gel chamber enhanced root and shoot biomass; however, the shoot growth was higher in the presence of NPs compared to its bulk counterpart. Moreover, greater phytotoxicity of ZnO from the source of NPs than bulk particles in shoot was observed. Scanning electron microscopy results showed a clear evidence of the penetration of NPs into root cells. ARTICLE HISTORY

SummaryIntroduction Seed germination is a complex physiological process regulated by genetic and environmental factors including temperature, water, oxygen, light and pH. Among them, temperature is one of the most important factors controlling the maximum rate and percentage of diaspore germination. Objective: The aim of the study was to determine the cardinal temperatures (Tb, To, Tc) of four Satureja species growing in Iran. Methods: Seeds of Satureja mutica Fish. et C. A. Mey., S. macrantha C. A. Mey., S. sahandica Bornm and S. bachtiarica Bunge were germinated at nine constant temperatures (from 0 to 40°C) with 5°C intervals. A factorial experiment based on completely randomized design with four replications was applied to determine the cardinal temperatures estimated by three regression models including intersected-lines (ISL), quadratic polynomial (QPN) and five-parameters beta (FPB). Results: The highest germination percentage (GP) occurred at 20°C for S. mutica (86%), S. macrantha (55%), S. sahandica (81%) and S. bachtiarica (89%), but there was no significant difference between 20 and 25°C, except S. sahandica. Germination stopped at 0°C and 40°C. The highest germination rate (GR), the lowest mean germination time (MGT) and time to 50% germination (D50) were obtained at 20-25°C for all species. The GRmfor S. bachtiarica was significantly (p≤0.05) higher than for three other species in all temperatures. None of the species did reach to 50% germination at temperatures higher than 30°C. Conclusion: Obtained results revealed the superiority of S. bachtiarica over the other species, v.s. S. macrantha was inferior. FPB and ISL models were most reliable for predicting cardinal temperatures, because of higher R2value and the lower root mean square error (RMSE). S. macrantha and S. mutica showed the lowest and the highest cardinal temperatures, respectively, in all three models.