Application of a process-based model to quantifying dormancy loss in seeds of Parrotia persica C.A. Meyer

Abstract

Information regarding germination and dormancy of Parrotia persica seeds is limited and there is no report on cardinal temperatures and germination modeling of this tree species. Thus, the main aims of this study were to model dormancy and germination of P. persica seeds and to identify the best way(s) to overcome seed dormancy in this species. Freshly matured seeds had spatulate, fully developed embryos (FA1 type) and the seed coat was water permeable. Fresh seeds germinated less than 20% at 5–30 °C, and gibberellic acid (GA) increased germination to about 40% at 5–30 °C, peaking at 53% at at 20 °C. Population thermal parameters (Tl and Th) had changed among dormancy breaking treatments. After-ripened seeds and those treated with GA had the lowest lower limit (Tl) and the highest higher limit temperatures which were 0.0 and 37 °C, respectively. The highest Tl and the lowest Th were observed in freshly matured seeds without any treatments (Control-MT) which were 24 and 26 °C; the narrowest temperature range for germination, implying the highest seed dormancy. Base (Tb) and ceiling (Tc) temperatures for the final germination percentage of non-dormant seeds were 0, and 40°C. Cardinal temperatures for the rate (speed) of germination of non-dormant seeds were almost the same as the observed values for final germination percentage. Seeds of P. persica must have Type 3 of non-deep physiological dormancy based on the graphical method, since Tb decreased and Tc increased as dormancy breaking progresses in a population. Population thermal parameters (Tl and Th) also showed the same change in different dormancy breaking treatments in which dormant seeds had higher Tl and lower Th than non-dormant seeds (after-ripened plus GA). For commercial usage or conservation projects, it is suggested to use a period of after-ripening followed by GA treatment to break dormancy.