Quantification of camelina germination niche to combined salinity and temperature stresses using a halothermal time model

The present work was carried out to quantify camelina germination niche under salinity and temperature ( T) stress using halotime and halothermal time models. Seed germination ( SG) time courses were recorded at six constant temperatures (5 °C, 10 °C, 15 °C, 20 °C, 25 °C, and 30 °C) and at each of the following levels of NaCl concentrations (0, 50, 100, 150, 200, and 250 mM). Halotime model could well describe the germination time courses across a range of NaCl concentrations ( R2 = 0.79–0.91). The median base NaCl concentration was approximately constant (231 mM) at suboptimal T followed by a linear decrease, with the rate of 17.4 mM °C−1, under supra-optimal T. However, the germination rate increased with increasing T, reaching its maximum at a fixed optimum temperature ( To = 20 °C), independent of NaCl concentration. Then it decreased linearly for T >  To and intercepted the x-axis at the ceiling temperature values of 33.5 °C, 30 °C, 28 °C, 25 °C, and 22 °C under 0, 50, 100, 150, and 200 mM NaCl, respectively. Consequently, based on model estimation the adequate soil T for SG of camelina should be in the range of 0.4 °C–33.5 °C, and the To is 20 °C. Besides, the salinity should be less than 231 mM.