Determination of temperature-related parameters and response ranges of Almolookhiyeh (Corchorus olitorius L.) seeds and seedlings using nonlinear regression

Almolookhiyeh (Corchorus olitorius L.) known in the world as a valuable medicinal plant that was produced for the first time in Iran in 2011. This study was aimed to quantify germination response of Almolookhiyeh to temperature. For this purpose، seeds were exposed to different constant temperatures (10، 15، 20، 25، 30، 35، 40، 45 and 50°C) in Seed Research Lab، Gorgan University of Agricultural Sciences and Natural Resources in 2011. Results showed that the effect of temperature on the maximum germination percentage (MGP)، germination rate (R50)، germination uniformity (GU)، and time to 10، 50 and 90 percent germination as (D10)، (D50) and (D90)، the percentage of normal seedlings (NS%) and seedling length (LS) was highly significant. Assessment of three nonlinear regression models including segmented، dent-like and beta models based on 10، 50 and 90 percent germination revealed that beta model was superior to other models. Based on the superior model (Beta)، base، optimum and ceiling temperatures were estimated as 10. 18، 37. 31 and 50°C، respectively. Biological hours also were calculated as 13. 56 hours. Using beta model to regress seedling length against temperature and normal seedling percentage versus temperature showed that seedling emergence، the maximum seedling length and the highest normal seedling percentage were occurred at 11 to 44، 35. 34 and 31°C، respectively.