Background: One of the most values of medicinal plants is Plantago ovata. That is belonging of Plantaginace family. Low and irregular germination is the most problem of medicinal plants which that occur in stage of germination under the low temperature at the first of spring.

 Objective: This study has evaluated the effects of plant growth promoting rhizobacteria on seed germination and seedling growth of Isabgol (Plantago ovate forsk), under low temperature conditions.

 Methods: This study was conducted as a factorial experiment in the form of randomizes complete design with four replications. The treatments consisted of different bacterial strains of pseudomonas (Putida 108, Fluorescens 112 and 11), Azotobacter Chroococum strains (5, 15 and 35), Azospirillum strains (lipoferum, Brasilense and Irakines), Mesorhizobium strains (Ic59, Ic2091 and SWRI7), control (without rhizobacteria infection) and temperatures (5, 10 and 20 c ۫ ).

Results: Germination parameters were significantly affected by temperature, bacterial strains and the interaction of treatments. In 5c ۫ temperature conditions, Psedumonas strains have the most effected on germination index, radicle and hypocotyl length, seedling vigor index, germination duration index.In 10c ۫ temperature conditions, the maximum germination percentages, germination rate, hypocotyl to radical ratio were obtained by using azotobacter and Mesorhizobium.