Effects of seaweed extract and nano-zinc oxide on seed germination characteristics and growth of tomato seedling under drought stress conditions

In order to study the effect of seaweed extract and nano-ZnO on germination characteristics of tomato seed, a factorial experiment was conducted based on a randomized complete block design. Preliminary germination and seedling growth tests were performed to determine the best concentration of seaweed extract and nano-ZnO. Experimental treatments included three levels of drought stress (0, 2- and 3-bar), four levels of application of nano-ZnO and seaweed extract (control, seaweed extract 4%, nano-ZnO 1200 ppm, and a combination of seaweed extract and nano-ZnO). The results showed that by decreasing the water potential standard germination percentage, seed germination rate, seedling length and dry weight, length and weight vigor indices decreased, whereas mean germination time increased. As the drought stress intensified, the amount of hydrogen peroxide accumulation was increased and also the activity of peroxidase and catalase enzymes in tomato seedlings increased. As well, application of seaweed extract and nano-ZnO at different levels of drought stress significantly reduced the negative effects of this stress on seed germination and the early growth of seedlings. Application of these compounds at different drought stress levels significantly increased the standard germination percentage, seed germination rate, seedling length and dry weight, length and weight vigor indices, but reduced seed germination time. Also, the use of seaweed extract and nano-ZnO under drought stress conditions increased the activity of peroxidase and catalase enzymes but reduced the accumulation of hydrogen peroxide in tomato seedlings.