Influence of Salinity and Temperature on Seed Germination of Indigofera tinctoria

Indigo is an unknown plant for most of people، and recently has derived attention due to its industrial and medical properties. There is scarce information about its seed germination response to temperature and salinity. This study was conducted to determine the effects of temperature and salinity stress on seed germination of Indigo. Therefore، two separate experiments were performed at the college of agriculture، Shahrood University of Technology، in 2011. In the first and second experiments germination response of seeds were determined over a wide range of temperatures (10، 15، 20، 25، 30، 35 and 40 oC،) and salinities (0 (control)، 2، 3، 4، 5 and 6 dS/m-1) respectively. The regression models fitted to the data of cumulative germination percent against time، and then time to 50% germination were dent-like، segmented، beta and quadratic functions. Based on indices like RMSD (root mean square of error)، correlation coefficient (R2)، and linear regression parameters، the segmented function was the best model to describe seed germination as a function of cumulative germination percent against time، and then time to 50% germination. The base، optimum and ceiling temperatures were 10. 27، 28. 26 and 39. 50 oC، respectively. The biological days (the minimum number of days required for germination under optimum temperature conditions) tended to be 1. 21. Application of low salinity levels (2 dS/m-1) increased the percentage and rate of germination، roots and shoots length and decreased roots and shoots weight of indigo. Also، with increasing salinity levels the percentage of germination and root growth was decreased. Higher levels of salinity decreased indigo root growth more than shoot growth.