چكيده انگليسي :
Drought stress is one of the environmental factors that limits plant growth, development and production and has negative effects on plant yield. It also can affect biochemical processes related to photosynthesis and by limiting this process in water shortage conditions, plant growth and ultimately its production reduce. To prevent drought damage to plants, silica compounds is used to increase plant resistance to drought stress. The purpose of this study was to investigate the interaction of drought stress (irrigation frequency) and soil application of different levels of potassium silicate based on the vegetative traits of pistachio seedlings (cv Qazvini). This research was conducted as a pot experiment in the greenhouse of Pistachio Research Institute located in Rafsanjan city. The executive stages of this research began in October 2020 and continued until the summer of 2021. The experiment was factorially performed in a completely randomized design. Experimental treatments included potassium silicate at four levels of 0, 25, 50, 75 (mg of pure silica per kg of soil) and irrigation interval at three levels of 3, 6 and 9 days with three replications. So, there were a total of 12 treatments and 36 experimental units. In this experiment, seedling height, seedling diameter, dried seedling percentage, leaf number, leaf area, fresh and dry weight of shoots and roots, water use efficiency (WUE), leaf relative water content (RWC), Na, K and Ca concentration and absorption amount in shoot root were measured. The results showed that the effect of drought stress was significant on all investigated parameters except shoot and root potassium, soil pH, soil EC and root Na, so that due to the stress, the percentage of dried seedlings and shoot Na, Soil K and root Ca in the 9-day irrigation cycle increased compared to the control treatment;however, seedling growth and height, lower and upper diameter of seedlings, leaf number, leaf area, leaf dry weight , shoot and root dry weight, (Leaves RWC), WUE of shoot and root decreased in 9 days of irrigation interval.The application of potassium silicate affected all investigated parameters, except the upper and lower diameter of the seedling, Ca and Na of shoot, soil EC, root K. So that 25 mg/kg levels of potassium silicate resulted the most amount of seedling height, leaf number, dried seedling, leaf area, leaf dry weight, stem dry weight, root dry weight, WUE 1 and 2, leaf RWC, root sodium as 16. 06%, 34%, 43%, 32.2%, 44.1%, 27.6%, 32.2%, 32.2%, 37.3%, 16.7%, 40.2% relative to the control ; however, soil pH, root Ca, shoot K with 5.2%, 69.2%, 16.6%, had the highest amount at the level of 50 mg/kg soil compared to the witness treatment .Furthermore, the heighest amount of soil K, as 40.1% relative to the control, was observed in the 75 mg/kg of potassium silica application. The interaction effect of potassium silicate concentration and irrigation interval on seedling height, seedling top diameter, leaf number, dried seedling percentage, leaf area, leaf, stem and root dry weight, WUE of shoot and total WUE was significant.
