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 degrees C, 10 degrees C, 15 degrees C, 20 degrees C, 25 degrees C, and 30 degrees 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 degrees C-1, under supra-optimal T. However, the germination rate increased with increasing T, reaching its maximum at a fixed optimum temperature (To = 20 degrees 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 degrees C, 30 degrees C, 28 degrees C, 25 degrees C, and 22 degrees 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 degrees C-33.5 degrees C, and the To is 20 degrees C. Besides, the salinity should be less than 231 mM.

Automated summary

This study quantified the germination niche of camelina under salinity and temperature stress using halotime and halothermal models. The halotime model showed good fit for germination time courses at different NaCl concentrations. The germination rate increased with temperature until reaching a maximum at 20°C, independent of NaCl concentration. The suitable soil temperature for camelina germination was estimated to be 0.4°C-33.5°C, with a median base NaCl concentration of 231 mM.