Journal of Soil and Plant Interactions

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Silicon (Si) is one of the beneficial elements for plants, which improves quantity and quality of yield, decreases evaporation and transpiration and enhances plant resistance to abiotic stresses. In order to evaluate the effect of Si and nano-silicon (N-Si) on growth, morphological and photosynthesis attributes of tomato, cultivar Falcato, an experiment was carried out in a hydroponic system, based on a completely randomized design, with two Si and N-Si levels (1 and 2 mM) and Si-free nutrient solution (as control), and four replications. Such traits as chlorophyll index (SPAD), photosynthesis, nutrient uptake, stem diameter, relative water content and morphological changes like density of trichomes were measured during the experiment. At the end of the experiment, fresh and dry weights and root volume were measured. Results revealed that Si was more effective than N-Si on fresh weight and mesophyll conductance. Concentrations of 1 and 2 mM Si increased fresh weight and mesophyll conductance, respectively. However, this concentration did not affect dry weight and relative water content significantly. N-Si was more effective than Si on photosynthesis and photosynthetic relative water content. The highest photosynthesis and lowest transpiration rate was measured in 2mM N-Si. Application of Si and N-Si decreased relative water content and the least water uptake was in 2mM N-Si treatment. In conclusion, Si or N-Si, with 20-30 nm particle diameter and optimum tomato growth conditions (without abiotic stresses) increased photosynthesis, fresh weight, relative water content and decreased nutrient solution uptake under hydroponics.

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In order to evaluate the effect of different levels of benzyladenine, nitrogen and salinity on growth characteristics of pistachio seedlings, cv. Badami Zarand, a factorial experiment with three factors: benzyladenine (0, 250 and 500 mg/L), nitrogen (0 and 100 mg N/kg soil as NH₄NO₃) and salinity (0 and 2000 mg NaCl/kg soil) was carried out as completely randomized design with three replications for 24 weeks under greenhouse conditions. Results showed that although salinity significantly decreased dry weight of shoots and roots of the seedlings, but application of 500 mg/L benzyladenine increased dry weight of shoots and roots by 125 and 86 percent, respectively. However, simultaneous application of nitrogen and benzyladenine increased dry weight of shoots and roots more than 3 and 2 folds, respectively. Results also showed that salt stress significantly decreased leaf area and length of root system. But simultaneous application of nitrogen and the highest concentration of benzyladenine increased leaf area and length of root system more than 3 and 2.5 folds, respectively. The results of triple effects also showed that although height, leaf number and stem diameter significantly decreased under saline conditions, but simultaneous application of nitrogen and benzyladenine resulted in more prominent increase of these growth characteristics than individual application of these treatments. Finally, it is concluded that simultaneous application of nitrogen and benzyladenine resulted in more effective reduction of harmful effects of salinity on growth characteristics of pistachio seedlings than application of these treatments alone.

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Salinity stress is a major factor limiting the plant growth and productivity. Strawberry is a perennial plant and one of the most important small fruits; it is considered as a plant sensitive to salinity. In order to investigate the effects of jasmonic acid and silica nanoparticles on the yield, growth and fruits characteristics of strawberry cv. Paros, an experiment was carried out with three levels of jasmonic acid (0, 0.25 and 0.5 mM) as the spray, three levels of silica nanoparticles (0, 1 and 2 mM), and two sodium chloride levels (0 and 50 mM). Therefore, a factorial experiment was designed based on a completely randomized design with three replications under hydroponic condition. In this study, the length of pedicel, root volume, the dry weights of shoot and root, the percent of the opened leaf stoma, some fruit traits (index color and firmness), leaf specific area, salinity tolerance index and yield were measured. The results showed that growth indices, yield and also, some fruit-related features of this cultivar were decreased by salinity. Application of jasmonic acid and silica nanoparticle improved the fruit quality, yield and morphological characteristics under both control and salinity conditions. Thus, the use of jasmonic acid and silica nanoparticles under salinity stress increased the root volume, crown dry weight, and yield by 49%, 146% and 57%, respectively. The best results were observed in the application of 50 mM jasmonic acid and 0.5 mM silica nanoparticles.