Most of agricultural lands in Iran are located in arid and semi-arid regions and are considered as saline soils. In order to investigate the interaction of salinity as well as potassium and calcium on the growth and yield of tomato plants, a factorial experiment was perfected in the form of randomized complete blocks, in hydroponic conditions, with three replicates per treatment. Experimental factors include salinity at three levels (0, 20, and 40 mM NaCl), potassium content form chloride, nitrate (0 and 15 mM), and calcium from chloride, and nitrate (with 0 and 10 mM (. The studied growth factors, including plant height, stem diameter, number of leaves, flowers and fruits and leaf chlorophyll decreased with increase NaCl. Treatment plants with Ca (NO3)2 at 40 mM NaCl, increased the shoot and root dry weight by 55% and 95%, respectively. In addition, application of Ca (NO3)2 in the medium with maximum salinity concentration resulted in an increase of 75% in chlorophyll content. The analysis of data showed that the increase of salinity was accompanied with increase sodium content level of tomato plants. However, the root potassium was observed to decrease. On the contrast to the root, potassium content showed no change in the organs from the root upwards. Also, the use of Ca (NO3)2 with 40 mM NaCl reduced Na+ content by 23% compared with plants treated only with 40 mM NaCl. According to the results, it seems that application of Ca (NO3)2 may improve chlorophyll content, dry weight, and modulate ion hemostasis and decreased the negative of salt stress in tomato plants.
