Study of dormancy breaking and factors affecting germination of Parapholis incurva (L.) CEHubb. as annual grass

Parapholis incurva (curved parapholis) is an annual grass that is widely increasing its distribution in areas of barley production in northern Iran. Laboratory experiments were conducted to evaluate the type of dormancy and the effect of different methods of dormancy breaking, to determine cardinal temperatures using nonlinear regression models, and to test the effects of other ecological factors such as drought, salinity, heat shock and pH on germination of curved parapholis seeds. The results showed that the best method for dormancy breaking is applying 75 ppm gibberellic acid + 30 s of sulfuric acid, with highest germination percentage (84 %). It was also demonstrated that temperature significantly affects the germination rate and germination percentage of curved parapholis. The highest germination percentage was obtained between 18 and 25 degrees C, while the lowest germination percentage occurred at below 5 degrees C and above 30 degrees C. Using a segmented model, the base, optimum and ceiling temperatures were estimated to be 1.25 degrees C, 23.29 degrees C and 35 degrees C, respectively. Seed germination declined as the osmotic potential increased from-0.6 to-1.2 MPa. With increasing drought stress and salinity stress, the germination percentage reached less than 50% at-0.88 and-0.84 MPa, respectively. The maximum germination percentage was observed at a pH of 6 and 7. According to this result regulating the soil microclimate (temperature) through field preparations, soil amendments and cultural practices can be employed to better long-term management of curved parapholis.