Effect of silicic acid on some morphological and physiological characteristics of Pelargonium graveolens L. under CaCl2 salinity stress

This research was carried out to evaluate the effect of silicic acid on geranium responses to CaCl2 salinity stress. The experiment was done hydroponically in pots filled with sand. Experiment was laid out factorially based on a completely randomized design with five replications. Factors consisted of daily application of 0, 15 and 30 mM CaCl2 and weekly application of 0, 0.5 and 1 mM silicic acid in nutrient solution. The results showed that increasing salinity levels decreased growth characteristics including plant height, stem diameter, number of leaves per plants, leaf area, leaf, stem and total dry weight. Silicic acid especially with 1 mM concentration alleviated the stress effects and improved growth parameters, dry weight and stress tolerance index. Oil percent decreased in plants grown in 30 mM CaCl2 compared with controls while it was not affected by silicic acid. However, oil yield decreased, as CaCl2 concentration in nutrient solution increased. In all CaCl2 concentrations, application of 1 mM silicic acid increased oil yield. Overall, the results showed that high concentration of CaCl2 induced stress in geranium, and weekly application of 1 mM silicic alleviated the stress effects and increased stress tolerance index.