Hydrothermal Time Model For Germination Of Gentiana Macrophylla Pall., Atropa Belladonna L. And Salvia Miltiorrhiza Bunge Seeds

In order to quantify seed germination requirements of Gentiana macrophylla Pall.,Atropa belladonna L. and Salvia miltiorrhiza Bunge, seeds were pre-treated and thenincubated at different temperatures and water potentials to establish hydrothermal time model.The optimal pre-treatment for these three traditional Chinese herbs were as follows: G.macrophylla seeds, soaked in1.5%KMnO4solution for10minutes; A. belladonna seeds,soaked in50℃water for6hours and then rubbed with fine sand; S. miltiorrhiza seeds,soaked in0.5%KMnO4solution for2hours and then soaked in CaCl2solution (100mmol/L)for12hours. Seed germination experiments were carried out at temperature regime of5,10,15,20,25and30℃to examine the impact of temperature on germination and establishthermal time model. Next, within the range of optimum germination temperature (20and25℃), seed germination experiments were commenced under water potential regime of0,-0.25,-0.5,-0.75,-1.0and-1.5MPa to establish hydro time model and evaluate the effect ofwater potentials on germination. The time of seed sowing and seedling emergence in Yanglingcould be predicted by parameters of germination models and meteorological data of Yangling.Testing experiments were done by simulating meteorological conditions of Yangling with fourstarting temperatures (5thMarch,3.0℃;15thMarch,5.4℃;25thMarch,8.1℃) to examine theaccuracy of these models and add correction coefficients if necessary.Experimental results showed that the optimum germination temperature for G. macrophylla is25℃and both the final germination (84.33±1.33%) and germination ratewere highest in the curve. The base temperature for G. macrophylla was6.88℃and thethermal time for50%germination was261.04±1.54℃·d.20℃was best for S. miltiorrhizagermination and the highest final germination for light and deep color seeds were81.47±0.75%and80.41±1.10%respectively, while the highest germination rate was achieved at25℃. Lightcolor seeds of S. miltiorrhiza had a higher base temperature (6.21℃) than the figure for deepcolor seeds (1.53℃) and required lower thermal time to reach50%of seed germination(74.33℃·d), compared with113.75℃·d for deep color seeds. The base water potential of S.miltiorrhiza light color seeds was-1.27MPa, higher than-1.58MPa for deep color seeds. At20and25℃, light color seeds of S. miltiorrhiza had hydrothermal time requirements of92.09and106.75℃·MPa·d, respectively, while the corresponding values for deep color seeds werelarger,158.76and142.45℃·MPa·d. Based on the meteorological data of Yangling, G.macrophylla seeds could be sown on21stMarch and reach50%germination on2ndMay.Corresponding dates for deep and light color seeds of S. miltiorrhiza were28thFebruary,29thMarch and18thMarch,10thApril, respectively. Compared with results of other researchers,we suggested that the sowing time for G. macrophylla remained unchanged. Germination forS. miltiorrhiza light color seeds was rapid and required high temperature and water potentialindicating that it can be sown later. However, germinating for S. miltiorrhiza deep color seedswas slower and these seeds had high resistance of chilling and drought and can be sown early.