Using nonlinear regression models to quantify germination response of annual savory (Satureja hortensis L.) to temperature and water potential

This study was conducted to quantify germination response of annual savory (Satureja hortensis L.) to temperature and water potential. For this purpose، seeds were exposed to different temperature (12، 15، 20، 25، 30، 35، 37 and 40°C) and water potential (zero، -0. 1، -0. 3، -0. 5 and -0. 7 MPa) treatments in Seed Research Lab.، Gorgan University of Agricultural Sciences and Natural Resources in 2013. Results indicated that temperature and water potential and interacted effects had significant effect on maximum germination percentage، germination rate (reciprocal time to 50 percent germination)، and time to 10، 50 and 90 percent germination. Along with water potential decrement، both germination percentage and rate decreased. With temperature increasing to optimum temperature، both germination percentage and rate increased، while it decreased from optimum temperature onward. Assessment of three nonlinear regression models including segmented، dent-like and beta models revealed that the last one was selected as the superior model. Based on the superior model (Beta)، base، optimum and ceiling temperatures were estimated as 7. 56، 23. 98 and 40°C، respectively. Biological hours for control treatment (zero potential water) was calculated as 91. 17 hours. Cardinal temperatures were not affected by water potential، but biological hours for germination was delayed as 17. 64 hours per each unit water potential increment.