Mohsen Zafaranieh - Department of Agriculture, Technical and Engineering, Velayat University, Iranshahr, Iran.
Seyed Masoud Ziaee - Department of Plant Production, Faculty of Agriculture, Higher Education Complex of Saravan.

This study was conducted to quantify the germination response of Capers Capparis spinosa L. to temperature and water potential. The seeds were germinated at seven temperatures (۵, ۱۰, ۱۵, ۲۰, ۲۵, ۳۰, and ۳۵ °C) and six water potentials (zero, -۰.۳, -۰.۶, -۰.۹, -۱.۲ and -۱.۵ MPa). Increased water potential and temperature decreased germination percentage and increased germination time. The results revealed that the dent-like function (RMSE = ۰.۲۴, R۲ = ۰.۸۲, and r = ۰.۸۶) is suitable for describing the response to temperature and water potential. Based on the dent-like model base, optimum and ceiling temperatures were estimated as ۸.۸۱ to ۱۱/۱۳, ۲۱.۳۰ to ۲۴.۸۸, and ۳۵.۲۲ to ۳۷.۵۵ °C, respectively. Biological hours for the control treatment (zero potential water) were calculated as ۵۲.۱۱ hours. The hydro time constant for SSG (θH), the middle value for the base water potential (Ψb(۵۰)), the standard deviation in base water in the water potential (σyb), and the thermal time constant for SSG (θT) spanned the values of ۰.۶۳–۲۴۳.۴۸ MPa h, −۰.۳–۲.۵۹ bar and ۳۴۳.۳–۱۳۴۴.۳ °C h, respectively. The hydrothermal time parameters were ۴۴۵.۱۲ bar °C h, −۲.۲۷۴ MPa, and ۸.۲۸ °C for θHT, and Ψb(۵۰), Tb in temperatures and water potentials, respectively.

Capers, Germination rate, Regression model, Dent-like model, Thermal time