Abstract
The germination process and seedling development are the determining steps in the plant lifecycle that are the most sensitive to adverse environmental conditions. Therefore, this study was conducted to explore the effects of temperature and osmotic potential on germination responses using threshold models and to establish an optimal priming protocol for improving tolerance responses against osmotic stress in early growth stages. The results demonstrated that osmotic stress of - 0.8 MPa significantly influenced the extent, timing, and speed of seed germination. In addition, priming treatments led to an enhanced performance of early growth stages in response to osmotic stress. Based on thermal-time and hydro-time models, the predicted physiological parameters of the median thermal-time at sub-optimal temperature ( θT(50) = 909.09 ∘C h), the median ceiling temperature for 50% germination (T(c(50)) = 39.29 °C), the common base temperature (T(b) = 7.88 °C), the constant thermal-time at supra-optimal temperature ( θT = 805.96 °C h), the threshold water potential (Ψ(b(50)) = - 1.13 MPa), and the hydro-time constant ( θH = 56.09 MPa h) quantitatively describe the tolerance threshold of the germination process under different osmotic and temperature conditions. The results also showed that the efficiency of seed treatments depended on the priming conditions, including temperature, duration, and also concentration of the priming agent. However, the treatments of gibberellic acid (5 days, 10 °C, 100 ppm), salicylic acid (5 days, 10 °C, 50 ppm), calcium chloride (3 days, 10 °C, 10 mM), potassium nitrate (3 days, 10 °C, 100 mM), and hydro-priming (3 days, 10 °C) were optimal protocols of each priming method, resulting in an increased seed vigor under osmotic stress. Hence, the predicted biological parameters could easily be applied to determine the physiological changes of germination under environmental factors over time. Also, results suggest that recommended osmo-, hydro-, and hormonal-priming treatments could be efficient methods for ameliorating the osmotic tolerance in the post-priming stages of this plant, especially in arid lands. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s12298-022-01229-w.