effect of nitrogen phosphorous and potassium fertilizer levels on yield, photosynthetic rate photosynthetic pigments, chlorophyll content, and nitrogen concentration of plant components of allium altissimum regel.

persian shallot (allium altissimum regel.) is one of the perennial medicinal and industrial plant which is naturally growing in high elevated lands. in order to evaluate the effects of different nutrient elements such as nitrogen, phosphorus and potassium on photosynthetic rate and pigment content of persian shallot; an experiment was conducted as factorial based on completely randomized design with three replications in agricultural research green house, collage of agriculture, ferdowsi university of mashhad during year of 2010. the factors included nitrogen application (as urea) with four levels (control, 70, 140, and 210 kg.ha-1), phosphorus (as super phosphate) with three levels (control, 50 and 100 kg.ha-1) and potassium (as potassium sulphate) with three levels (control, 25 and 50 kg.ha-1). results indicated that a significant increase in wet and dry matter of bulb yield and chlorophyll content with increasing nitrogen. nitrogen, phosphorous and interaction of nitrogen and phosphorus caused an increase in photosynthesis rate of persian shallot. however, potassium did not have any significant effect on studied characteristics that might be because of enough potassium content in the soil. results of soil analysis and straw stem and leaves after harvesting showed no significant differences in nitrogen concentrations of samples in different levels of fertilizers. with increasing nitrogen application, the content of bulb nitrogen significantly increased. therefore, the highest concentration of nitrogen in bulbs with 2.3% was observed in the highest nitrogen application level treatments.