Growth, Survival, Protein Content, and Phytoremediation Potency of Various Rangeland Plant Species (Medicago polymorpha L., Medicago rigidula L., and Onobrychis sativa L.) Grown in Vermicompost-Containing Potting Media

A pot experiment based on completely randomized factorial arrangement design with four replications was conducted under greenhouse condition at Malayer University, Malayer, Iran. Pots contained a mixture of soil and different concentrations (0% and 60% w/w) of vermicompost. Plants were exposed to three lead nitrate concentrations: 0, 4, and 8mM. Based on the results of this research, shoot height and root length of the studied plants significantly decreased with increased lead concentrations in all vermicompost application levels. Generally, plants exposed to lower levels of lead and vermicompost application had higher root:shoot ratio. The survival capacity of all the studied plants was significantly reduced with increased lead concentrations, but increased with increased vermicompost application level. The total protein content increased with decrease in lead nitrate concentration, but decreased with decrease in vermicompost application. Generally, translocation factor increased significantly as vermicompost application rate increased. The highest root concentration factor of lead was found in V1xPb2 as compared to the other treatment levels. Generally, tolerance index values of all the studied plants were significantly higher in the lower lead concentration treatments.