Determining the optimal model for improving seed germination and seedling vigor of perennial grasses

Success of seed germination and seedling establishment of perennial grasses, which are sensitive to environmental stresses, is of great importance in the renovation and amendment of pastures. To achieve this, seed priming technique was evaluated in improving germination rate and seedling vigor of five perennial cool season grasses including Bromus confinis, Elymus elongatum, Agropyron pectiniforme، Festuca ovina، Festuca arundinaceae using Polyethylene Glycol 8000 for 0, 0. 5, 1, 1. 5, 2, and 2. 5 MPa concentrations and 0, 2, 4, 6, and 8 days duration (D). The study was conducted as a factorial experiment based on CRD with four replications. ANOVA results showed that there were significant differences between all studied traits and their interactions for germination rate and seedling components (P<0. 01). Seed priming significantly increased germination rate comparing with the control (non primed), so that there were 127. 9, 77. 8, and 66. 5% increase in germination rate comparing with the control (2 days in 2 MPa) for B. confinis, A. pectiniforme and E. elongatum, respectively, and 96. 5% increase for F. arundinaceae (6 days in 1. 5 MPa) whereas the lowest increase in germination rate (15%) was observed for F. ovina (4 days in 2. 5 MPa). The regression analysis revealed that increasing PEG concentration decreased shoot and root dry weight for all species except F. arundinaceae and F. ovina. The greatest seedling growth reduction was detected for large seeded species B. confinis, and E. elongatum when treated for long duration (more than 2 days) and low concentrations of PEG. Overall, The results of this study suggested that seed priming with higher concentrations of PEG about 2 and 2. 5 MPa and 2 days seed storage duration plays an important role in the success of grasses seed priming technique and also it revealed that small seeded species might show a better response to priming in improving seed germination and seedling establishment than that of large seeded ones.