Germination response study of tall morning-glory (Ipomoea purpurea (L.) Roth), an invasive weed, to temperature and water potential

A laboratory study was conducted at Golestan plant protection management in 2013 to determine the effect of temperature and water potential on seed germination of tall morning-glory. Treatments were consisted of seven levels of temperatures (10, 15,25,30,35 and 40 0C) and six levels of water potential in (0, -0.2, -0.4, -0.6, -0.8 and –1.0 MPa). Seed germination began at 100C up to 250C, and then started to decrease. The highest seed germination (84%) was obtained at alternating temperatures of 25:35 °C. By reducing water potential from 0 to -1.0 MPa, seed germination percentage was decreased from 80% to 0. On the basis of three- parameter logistic model, the salt concentration required for 50% reduction of seed germination was -6.5 MPa. The Segmented model used to determine cardinal temperatures of tall morning-glory. Based on this model, base, optimum and ceiling temperatures of the plant in control treatment were 8.3, 25, 40 0C respectively. In general, the optimal temperature range, germination occurred in less water potential. By reducing water potential, base, optimum and biological hours for germination was increased.