Determination of the Cardinal Temperatures and Studying the Effect of Temperature on the Efficiency of Priming on Onion Seed (Allium Cepa cv, Zargan)

In order to study the effect of priming on onion seed germination of Zangan Cultivar in different temperature conditions, this study was carried out with 6 levels of temperature of 5 to 30 ° C and three seed pretreatment, include control, hydro-priming and halo-priming with 0.5% potassium nitrate with three replicate. The results showed that priming treatment with potassium nitrate (0.5%) could be effective on germination components. Primed seeds with potassium nitrate (0.5%) showed more germination at all temperatures. Potassium nitrate (0.5%) treatment also affected the germination reaction to temperature. These seeds showed 33.6% more germination than the other two treatments at 5°c. The results showed that germination percentage at 20°c in all treatments reaches its maximum and then remained relatively constant. In evaluating the segmented model for predicting cardinal temperatures, seed germination at base, optimum and ceiling temperatures was 1.7, 27.38, 46.09°c(in potassium nitrate (0.5%) treatment), 1, 25, 43°c (in hydro-priming treatment) and 1.9, 27.6, 46.12°c (in control treatment). For predicting time of germination at different constant temperatures used Thermal-time that constant coefficient of Thermal-time was 1872.79(°Ch).