Hydrothermal time analysis of watermelon (Citrullus vulgaris cv. 'Crimson sweet') seed germination

This study evaluated the ability of a hydrothermal time model (HTT) to describe the kinetics of watermelon (Citrullus vulgaris cv. 'Crimson sweet') seed germination under different temperatures (T) and water potentials (psi) and also to determine the cardinal temperatures of watermelon. Results indicated that psi influenced germination rate and germination percentage. For this seed lot, cardinal temperatures were 10 degrees C for Tb, 28.34 degrees C for T-o and 40.8 degrees C for T-c in the control (0 MPa) treatment. There was a decrease in hydrotime constant (hH) when T was increased to T-o and then remained constant at supraoptimal temperatures (30 MPah(-1)). Also, at temperatures above T-o, psi(b(50)) values increased linearly with T. The k(T) value (the slope of the relationship between psi(b(50)) and T exceeds T-o) of this seed lot was calculated as 0.076 MPa degrees Ch(-1). Results this study show that when the HTT model is applied, it can accurately describe psi(b(g)) and the course of germination around T-s (R-2 = 0.82). Moreover, the psi(b(50)) was estimated to be -0.96 MPa based on this model. Consequently, the germination response of watermelon for all Ts and psi(s) can be adequately described by the HTT model and enabling it to be used as a predictive tool in watermelon seed germination simulation models.