Effect of associative bacteria on element composition of barley seedlings grown in solution culture at toxic cadmium concentrations

The response of barley seedlings to inoculation with associative rhizobacte ria Azospirillum lipoferum 137, Arthrobacter mysorens 7, Agrobacterium radi obacter 10 and Flavobacterium sp. L30 was studied in hydroponic and quartz sand cultures in the presence of 50 mu M CdCl2,. Cadmium caused severe inhi bition in the growth and uptake of nutrient elements by the plants. Inocula tion with the bacteria slightly stimulated root length and biomass of hydro ponically grown Cd-treated seedlings. The bacteria increased the content of nutrients such as P, Mg, Ca, Fe, Mn and Na in roots and or shoots of the p lants grown in the absence of Cd. Positive changes in the element compositi on caused by the bacteria were less pronounced in Cd-treated plants, wherea s the total amount of nutrients taken by the inoculated plants was generall y increased significantly. The content of Cd in the inoculated plants was u nchanged, except increased in roots upon addition of A. lipoferum 137. Inoc ulation did not affect the activity of peroxidase, alpha-mannosidase, phosp hodiesterae, alpha-galactosidase, and concentration of sulfhydryl compounds used as biochemical markers of stress in plant roots. The results showed t hat associative bacteria were capable of decreasing partially the toxicity of Cd for the barley plants through the improvement in uptake of nutrient e lements.