In this study, water stress was applied by polyethylene glycol at a concentration of 20 perecentage. To improve the resistance of the plants, the samples were treated by potassium nitrate at concentrations 5, 10, and 15 mM within 9 days. Changes in proline, total protein, photosynthetic pigments, carotene, anthocyanin, malondialdehyde, phenols, flavonols, flavonoids, soluble sugars and potassium ion were examined. The results showed that tobacco plants which had been exposed to drought used the accumulation of osmolytes such as proline, soluble sugars and potassium in order to balance their osmotic pressure. Drought stress also caused oxidative stress and increased the production of active forms of oxygen. As a result, non-enzymatic antioxidant defense system of tobacco plants including anthocyanins, flavonoids, flavonols and beta-carotene increased, which could be considered to be a major step for resistance to drought. The results also showed that the concentration of 15 mM potassium nitrate in particular, could significantly improve some of the harmful effects of stress and reduced photosynthetic pigments and proteins. Potassium nitrate could also bring down the MDA and beta-carotene levels to equivalent levels in control plants. As a result, it seems that using potassium can affect plant resistance to drought and plays an important role to reduce some harmful effects of stress.

The present study aimed to increase the seed germination and the initial performance of pistachio seeds by investigating the effects of the magnetic field and osmopriming treatments simultaneously. 10 treatment levels of 10, 20 and 30 mT for 5, 15, 25 minutes and 1 control treatment (without exposure to a magnetic field) were performed in three replicates and the best level of magnetic surface was selected. The results showed that seeds subjected to the magnetic field showed an increase in plumule length, radicle length, total length of seedlings, fresh and dry weight of plumule as well as radicle and germination speed compared with the control treatment. However, there was no significant difference in the germination percentage and uniformity of seeds. Magnetized seeds, with the superior selective treatment (10 mT for 15 minutes), were primed with solutions of potassium nitrate, humic acid and salicylic acid at levels of 10, 25 and 40 mM and a control level (the best level of magnetism) in three replicates. The best result was obtained from humic acid (25 mM). With regard to the low cost of the purchase or construction of magnetic devices and their positive effects, their application could be recommended (10 mT for 15 minutes) combined with the humic acid (25 mM)) so that the quality of pistachio seedlings production would be increased.