Interactive effect of Salinity and Urea Fertilizer on Some Physiological Characteristics Quality and Quantity Yield of Marsh Mallow (Althaea afficinalis)

Nitrogen is the first nutrient element that has a shortage in saline areas. Therefore, the correct management of nitrogen fertilizers is a suitable strategy to increase plant tolerance to salinity stress. This experiment was carried out in a completely randomized design in a factorial experiment on of Isfahan University of Technology, with three replication in 2017. Salinity stress was applied at four levels of 0, 2, 6 and 10 dS/m NaCl and nitrogen at four levels of 0, 50, 100 and 150 kg.ha-1. Result showed the amount of photosynthetic pigments increased with nitrogen application under salt stress conditions. The highest total chlorophyll content was related to control treatment and 2 dS/m of salinity treatment both under 150 kg N.ha-1, which was 18.20 and 17.63 mg/g leaf fresh weight respectively. Result of interaction salt and nitrogen showed highest sodium concentration and Na+/K+ and Na+/Ca2+ ratios were related to 10 dS/m salinity and no nitrogen application, which was respectively 342, 546 and 763% higher than the control treatment, while the highest amount of calcium was related to non-stress treatment and 150 kg N.ha-1. The interaction between salinity and nitrogen levels showed that the highest height was related to salinity treatment 2 dS/m and consumption of 100 kg N.ha-1, which increased 65% compared to the control. The highest area and number of leaves per plant were related to non-stress treatment and 150 kg.ha-1 nitrogen which was 56% and 60% higher than the control treatment, respectively. The highest shoot dry weight was related to non-stress treatment and 50 kg.ha-1 nitrogen. The highest leaf mucilage was related to non-stress treatment and consumption of 150 kg N.ha-1, which increased 171% more than control treatment. From the results of this study, it can be concluded that shoot dry weight and leaf mucilage weight decreased significantly under salinity increasing. At least partly was due to the toxic effects of chlorine and sodium ions because such changes impair the photosynthetic activity of the plant, resulting in a decrease in dry weight and leaf mucilage; However, the use of nitrogen fertilizer up to 100 kg.ha-1 can reduce the negative effects of salinity stress.