Effects of lead ions on germination, initial growth, and physiological characteristics of Lolium perenne L. species and its bioaccumulation potential

The present study was conducted to investigate the responses of Lolium perenne L. species to lead ions. To do this, the effects of lead ions at five levels: control (blank), 250, 500, 750, and 1000 mg/kg or mg/L (depending on germination in the soil or petri dish) on the germination, initial growth, and physiological characteristics of Lolium perenne were investigated. The results showed that the difference between various lead concentrations was statistically significant at 1% confidence level in all of the germination, vegetative, and physiological characteristics. In addition, the results of translocation and stress factors indicated that there was a significant difference between the control treatment and the concentrations of 250, 500, 750, and 1000 mg/L of lead ions. Results show that the mean value of stress, which was 0.3196 in the control value, reached 0.4154 at the concentrations 1000 mg/L. Different levels of lead ions had significant effect on the estimated characteristics including germination percentage, seed vigor, germination index, chlorophyll a, chlorophyll b, carotenoids, root, and shoot. The average germination percentage in the control was 46.66%, which decreased by 5% at the highest lead concentration. In addition, the average of seed vigor, which was 34.06 in the control conditions, decreased to 0.72 at the highest lead concentration. Also, the chlorophyll a dropped from 0.5261 mg/g in the control conditions to 0.3149 mg/g. On the other hand, increase in lead ion concentration affected the physiological characteristics of Lolium perenne species. Results suggest that Lolium perenne is capable of accumulating lead and is well tolerant to lead in soil. Therefore, it is concluded that it can be used for sowing on lands which are polluted to this heavy metal (up to the concentration of 1000 mg/kg).