Effects Of Hydro-Priming On The Germination And Emergence Of Kentucky Bluegrass(Poa Pratensis) Varieties

Slow and inconsistent germination is a critical problem for establishment of the turf grass Kentucky Bluegrass (Poa pratensis). A series of experiments were conducted in the laboratory and greenhouse with four commercial Kentucky Bluegrass varieties (Butterfly, Kentucky, Blue Chirp and Park) using the hydro-priming method. The objectives were to study (1) optimum temperature condition for hydro-priming;(2) effects of priming on seed germination, seedling emergence and establishment;and (3) response of different varieties to the same priming approach.The results from daily observations of seed soaking treatments at 10℃, 15℃ and 20℃ showed that the optimum priming conditions for the tested varieties was soaking seeds at 20℃ for 5 days. The effects of priming varied with variety. The positive effect based on a germination index parameter was: Park (336.7%) >Blue Chirp (205%) >Kentucky (116.4%) >Butterfly (45.4%).Priming (20℃ for 5d) significantly (P<0.05) enhanced the seed germination of test species at 20℃ in a laboratory test. However, the extent of this effect differed with variety and parameters measured. Compared with the non-treated control, final germination percentage of primed seed increased 4%-7%, a significant difference (P<0. 05) for all varieties except Blue Chirp. There was a significant (P<0. 05) increase in the germination index of 45% (Butterfly) to 205% (Blue Chirp). The number of days to reach 50% germination decreased by 1-3 days and was significant (P<0. 05) for Blue Chirp and Park. The priming effect on increasing cumulative germination lasted until day 6 (Butterfly) to day 15 (Blue Chirp).Hydro-priming markedly increased the free sugar contents for the first 72 h and promoted the seedling growth rate for 18 d.The greenhouse experiment was conducted at 15/25℃ and 10/20℃ and showed that the seedling emergence rate, plant coverage and number of tillers were significantly (P<0. 05) increased by hydro-priming. The seed vigor of primed seed was higher than that of control seed when the four varieties were averaged over two temperatures. E. g. the seedling emergence increased 26%-73% three weeks after sowing;the plant coverage over the ground increased 6. 4%-9. 9% seven weeks after sowing. In the same period, the number of tillers increased 33%-40%. Hydro-priming also reduced the time required for 30% seedling germination by 4 days. However, neither shoot height nor time of emergencewas affected by hydro priming.The impact of hydro priming on the greenhouse experiment' s index varied with variety and temperature. In general, the priming effect in sub-optimal conditions (10/20°C) was higher than that in optimum conditions (15/25°C). For varieties, the priming effect was greater on Park and Blue Chirp than on Butterfly and Kentucky.