Maryam Mazaheri-Tirani

Seed germination and survival of seedlings are very sensitive to heavy metals. This study investigated effects of commercial micron ZnO (˂1,000 nm) and nano ZnO (25 nm) on Ajwain (Carum copticum L.). Seeds were treated with eleven concentrations of micro and nano ZnO (0, 0.04, 0.2, 2.5, 5, 10, 50, 100, 500, 1000 and 2000 ppm). The number of seeds germination in 14th days with 2 d intervals after incubation was measured. Then, quantitative traits were investigated after 21 days. Our results showed that micron and nano-sized ZnO concentrations at lower than 5 ppm concentration improved the seedlings elongation and some growth indices, but concentrations higher than 10 ppm levels of m-ZnO or n-ZnO acted as the main limiting factors for seed germination, and declined survival seedlings rate. Overall, micro ZnO treatments had a more negative effect on seedlings growth compared with that of ZnO. The concentrations above 100 ppm of the two forms of ZnO resulted in agglomeration into media.