Application of hydrothermal time model to determine the cardinal temperatures for seed germination in wild mustard (Sinapis arvensis) during dormancy elimination.0

In order to investigate the variation in germination rate, cardinal temperature and hydrothermal time parameters of wild mustard seed in different water potentials were designed and implemented during the study in gorgan university of agricultural sciences and natural resources, in 2017 as a split plot done in a completely randomized design with three replications of the municipality. In this research, germination modeling was performed well. To describe the germination rate response to temperature in different potentials of water 0, -0.2, -0.4, -0.6, -0.8 MPa were used from the dent-like function. By applying different concentrations of gibberellic acid (100, 300, 500, 1000, 1500 and 2000 ppm), the process of germination changes in the studied temperatures was incremental, so that the highest germination percentage was related to gibberellic acid 2000 ppm. By reducing the potential at each level of gibberellic acid, the base temperature increased and the lower and upper optimum temperature and the ceiling temperature decreased. The hydrotime coefficient in control seeds decreased significantly with increasing temperature and the water potential was increased. The hydrotime coefficient and base water potential increased with decreasing gibberellic acid. The results showed that the coefficients obtained by the hydrothermal time model were of relatively high precision and the constant value of hydrothermal time, base water potential and base temperature in control seeds were 1173.83 MPa ºC h-1, -0.09 MPa and 3.07 °C and for gibberellic acid with concentration of 2000 ppm were 315.57 MPa ºC h-1, -0.50 MPa and -1.22 ºC, respectively. Changes in the base water potential for 50% of germination in gibberellic acid 1500 and 2000 ppm treatments had a two segmented trend up to 20 °C so that it -0.7 to -0.6 MPa and increased above 20 °C the maximum value at 30 °C.