A pot experiment was conducted during 2014 seasons at the field of Seed and Plant Institute, Karaj, Iran, to study the effect of sulphur application (with and without thiobacillus) on the physiological and chemical response of stone fruit rootstocks (Prunus L.) including "Myrobalan","GF 677", "Penta" and peach seedling rootstock (native) grown on two selected calcareous and alkaline (with pH values greater than 7) soil series of Karaj province. The experiment was laid out in a split- split plot experiment in the randomized complete blocks design with three replications. The main plot treatments included twodifferent soil textures (silty clay loam and loam with pH 8 and 7.3, respectively) while the sub plot treatments were four stone fruit rootstocks (Prunus L.) including "Myrobalan","GF 677", "Penta" and peach seedling rootstock (native) and finally six different levels of sulphur application (sulphur application of 0, 500 and 1000 g/pot with and without thiobacillus of 10 g/pot) as sub-sub factor. Statistical analysis of data indicated that the factors alone and together had a significant effect on leaf mineral content, shoot number/rootstock and shoot length of studied rootstocks. The effects of two-fold and three-fold interactions were also significant in these attributes (except for the interactive effects of soil texture × sulphur application and rootstock × sulphur application for shoot number/rootstock). Mean comparisons of the three-fold interaction effects between factors showed that these attributes had higher average value than the control treatment (without any sulphur and thiobacillus application). Also, the results of the project showed that application of 500 g sulphur/pot and/ or 10 g thiobacillus/pot would increase the chlorophyll fluorescence parameters, leaf surface, and leaf SPAF-value.
Key words: Sulphur application, stone fruit rootstocks (Prunus L.), physiological and chemical response.