Maryam Mazaheri-Tirani - Department of Biology, Faculty of Science, University of Jiroft, Jiroft ۷۸۶۷۱-۶۱۱۶۷, Iran
Soleyman Dayani - Department of Agricultural Biotechnology, Payame Noor University (PNU), P.O. Box ۱۹۳۹۵-۴۶۹۷ Tehran, Iran,

Seed germination and survival of seedlings are very sensitive to heavy metals. This study investigated effects of commercial micron ZnO (˂۱,۰۰۰ nm) and nano ZnO (۲۵ nm) on Ajwain (Carum copticum L.). Seeds were treated with eleven concentrations of micro and nano ZnO (۰, ۰.۰۴, ۰.۲, ۲.۵, ۵, ۱۰, ۵۰, ۱۰۰, ۵۰۰, ۱۰۰۰ and ۲۰۰۰ ppm). The number of seeds germination in ۱۴th days with ۲ d intervals after incubation was measured. Then, quantitative traits were investigated after ۲۱ days. Our results showed that micron and nano-sized ZnO concentrations at lower than ۵ ppm concentration improved the seedlings elongation and some growth indices, but concentrations higher than ۱۰ 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 ۱۰۰ ppm of the two forms of ZnO resulted in agglomeration into media.

Heavy metal, ZnO, nanoparticles, toxicity, Ajwain, seedlings survival