Effect of Temperature on Germination Rate of Russianthistle (Salsola kali L.) Based On Regression Models

Salsola kali L. is a summer annual broad-leaved weed and C4، salt and drought-tolerant species belonging to Chenopodiaceae family. It is a prolific seed-producing weed. In order to investigate the Germination cardinal temperatures of Salsola kali L.، seeds were collected from North Khorasan (faroj) and Razavi khorasan (mashhad) and a laboratory experiment was conducted at constant temperatures including، 5، 10، 20، 30، 35، 40 and 45 °C with a daily alternating photoperiod (12 h light/12 h dark) in a completely randomized design with four replications in Ferdowsi university of Mashhad. To determine the cardinal temperatures for seed germination، nonlinear regression methods of Quadratic Polynomial (QPN)، Intersected-lines (ISL) and Five-parameter Beta (FPB) models have been used. The highest germination percentage was within the range of 10-40 °C، while the highest germination rate occurred in the 20-40°C range. FPB and ISL models showed most suitable fit based on highest R2adj for Razavi Khorasan and North khorasan، respectively. The cardinal temperatures for North khorasan seeds were 2. 35، 34. 8 and 48. 35 °C and for Razavi Khorasan were 2. 63، 32. 55 and 45. 42 °C. By These results، the broad temperature range of germination and invasion ability for this weed would be indicated.