Application of hydro-time model for quantification of Brassica napus L. germination response to water potential and temperature

Introduction Drought stress is one of the most important environmental factors to reduce the growth, yield and yield components of many crops, especially in arid and semi-arid regions of the world.Temperature is very important for seed germination. There for it can be said, and water potential are two primary environmental regulators of seed germination. Quantification of germination response to water potential at different temperature is possible using hydro time model. In this study, with using hydro time model quantification of Brassica napus L. germination response to water potential and temperature. Material and methods In this study germination response of Brassica napus L. to water potential at different temperature were studied. Experiments were conducted in 2017 on Brassica napus L. (Okapi) at the seed laboratory of Yazd Agricultural and Natural Resources and Education Center, AREEO, Yazd, Iran. Treatments included drought levels (0, -0.2, -0.4, -0.6 and -0.8 MPa) in temperatures of 10, 15, 20, 25 and 30 °C. The response of cumulative germination seeds to different potentials at different temperature was quantified using normal function. All data were analyzed by SAS ver 9.2. The hydro time model was fitted to cumulative germination. Goodness of fit of the hydro time models to all data was checked by constructing plots of the coefficient of determination (R2), the relationship between the observed and the predicted germination percentage and base water potential. Results Results indicated that germination percentage increased with increasing temperature to 25 °C in all water potentials, while germination percentage and germination rate reduced as a result of water potential increment. The highest germination percentage (94 %) was obtained from control conditions at 20 and 25 °C. The minimum germination percentage (zero) was attained at 30 °C and -0.8 Mpa. Results indicated that, The hydro time constant (θH), base water potential, standard deviation of base water potential in population and the coefficient of determination (R2) for 10 °C were 81.34 Mpa h, -0.75 Mpa, 0.41 and 0.89, for 15 °C were 52.17 Mpa h, -0.82 Mpa, 0.47 and 0.70, for 20 °C were 28.71 Mpa h, -0.91 Mpa, 0.44 and 0.71, for 25 °C were 17.54 Mpa h, -0.81 Mpa, 0.42 and 0.73 and for 30 °C were 11.24 Mpa h, -0.52 Mpa, 0.35 and 0.82, respectively. The hydro time constant (θH) declined significantly with increasing temperatures, so that the minimum hydro time constant (11.24 MPa h) was attained at 30 °C. The increment of temperature resulted in significant reduction of base water potential, and the highest base water potential (-0.91 MPa) was obtained at 20 °C, and the minimum base water potential (-0.52 MPa) was attained at 30 °C. The minimum standard deviation of base water potential in population (0.35) was obtained at 30 °C, using hydro time model for quantitation of Brassica napus L. Conclusion Germination response to water potential at different temperatures, led to acceptable results. Utilizing the output of hydro time model at different temperatures can be useful in prediction of germination percentage of Brassica napus L. in different water potential.