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The purpose of this study was to investigate the effect of Damavand volcanic ash on the morphological and physiological characteristics of beans as a factorial experiment in a completely randomized design. The results showed that the highest dry leaf weight was observed in 100 mg/L treatment per liter of volcanic ash (0.0099 g). The results also showed that the optimal sugar content of the soluble sugar at 100 mg/L of volcanic ash was 0.650 (mg/g D.W.). The highest protein content and optimal peroxidase activity were observed with 0.68 (mg/g F.W.) and 0.082 (A470/mg/protein), respectively. Therefore, it can be argued that volcanic ash may increase plant growth and biosynthesis of organic compounds such as iron and aluminum.

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One of the major abiotic stresses that negatively affects plants is the presence of heavy metals. Soil pollution with heavy metals, resulting from the industrial development and use of fertilizers containing heavy metals, has become a major environmental concern in human societies. Mercury is a toxic heavy metal that causes pollution in agricultural lands. Accumulation of Hg by plants may disrupt many cellular functions and block growth and development. Under such conditions, the enzymatic and non-enzymatic defense systems of plants are activated. Several defense systems are cooperating together in plants to cope with stressful situations. In this study, the effect of different concentrations of mercury on the photosynthetic pigments content and non-enzymatic defence systems in Nicotiana tabacum was studied. After planting the plants under the same conditions in the hydroponic medium and feeding the plants with Hoagland solution, treatments with different concentrations of mercury nitrate (0.5, 1 and 3 mM and a control group) were applied to the seedlings in three replications. Ten days after the application of the treatments, the plants were harvested and examined. The results showed that tobacco plants which had been exposed to heavy metal used the accumulation of osmolytes such as proline and soluble sugars in order to balance their osmotic pressure. The decrease in the amounts of photosynthetic pigments and increase in the levels of malondialdehyde in the leaves indicated the elevation of oxidative damage. Increased activity of non-enzymatic antioxidants in tobacco leaves, including anthocyanins, phenol, flavonols and flavonoids, can be interpreted as the mechanisms of resistance to heavy metal stress induced by mercury.