Evaluation of morph-physiological and biochemical responses of marshmallow (Althaea afficinalis L.) to foliar application of iron and zinc under saline condition

To investigate the effect of zinc and iron foliar application on the morph-physiological and biochemical traits of marshmallow (Althaea officinalis L.) under salinity, a factorial experiment was conducted based on a completely randomized design with three replications in Esfahan Agriculture and Natural Resources Research and Education Center, Iran. The factors included NaCl at 3 levels of 0, 4 and 8 dS/m, zinc sulfate at 3 levels of 0, 1.5 and 3 ppm and iron sulfate at 3 levels of 0, 1.5 and 3 ppm. The sodium and potassium content was measured using a flame photometer. The iron and zinc content was measured using an atomic absorption spectrometer. The mucilage was dried to determine its weight and total phenol was measured using a spectrophotometer. With increasing salinity, the amount of potassium, zinc and iron significantly (P ≤0.01) decreased but the sodium content increased. With increasing the zinc concentration in saline and control conditions, the potassium amount significantly (P ≤0.01) increased. Foliar application of zinc and iron significantly (P ≤0.01) increased the zinc and iron amount in the leaves. Although flowers fresh weight was reduced under saline condition compared to non-stress conditions, the zinc and iron spraying mitigated the effects of stress. Also, mucilage content was increased by 49 and 20% under 8 and 4 dS/m salinity, respectively, in comparison with non-stress conditions. The iron and zinc spraying significantly (P ≤0.01)increased the amount of mucilage. With increasing salinity, the phenol content significantly (P ≤0.01) increased and the highest content of phenol (65.2 mg / ml) was observed in the salinity of 8 dS/m3 + 3ppm of iron sulfate + 0 ppm of zinc sulfate. Generally, spraying of iron and zinc sulfate in saline conditions not only improved the nutritional status of marshmallow, but also increased the flowers yield and mucilage.