Germination of melon seeds under water and heat stress: Hydropriming and the hydrotime model

Since hydropriming is considered a more economical process and easier to use commercially, it was chosen as an alternative to osmopriming to improve the germination of melon seeds under hydro and thermal stress. The hydro-time model was used in interpreting the effects of hydropriming over melon seed germination. The objectives of this study were: a) to calculate the hydro-time model's parameters, including the changes induced by hydropriming and, b) to assess effectiveness of hydropriming over germination under conditions of hydro and thermal stress. The parameters of this model were theta(H) = 0.982 MPa d y Psi(b(50)) = -0.640 MPa for the control seeds and theta(H) = 0.615 MPa d y Psi(b(50)) = -0.547 MPa for seeds treated by 16 hours of hydropriming with a sigma(Psi b) = 0.23 MPa in both cases. Hydropriming significantly reduced the hydro-time and increased germination rate under water stress conditions without affecting the percentage of germination. The treatment increased the percentage of germinated seeds and reduced the mean time to germination (T-50) throughout the entire range of studied temperatures. Only treated seeds germinated at 10 degrees C. Thus hydropriming could be used to improve germination of melon in field conditions.