EFFECTS OF COLD STRATIFICATION ON THE ENDOGENOUS HORMONE, DORMANCY AND GERMINATION OF CORNUS WALTERI WANGER SEEDS

The most critical phase in plant life is the germination period, which is influenced by both intrinsic and environmental factors. Assessment of cold stratification on several endogenous hormone, IAA, abscisic acid (ABA), gibberellin GA1/3 (GA1/3), zeatin-riboside (ZRs) and isopen-tenyl adenine (iPAs), and germination of Cornus walteri Wanger. seeds was done. Relationship between endogenous hormone and seed germination and mechanism of seed dormancy of C. walteri were also analysed. The results showed that the significant fluctuatation of both IAA and iPAs content was fond during cold stratification period, while the variation of ZRs was little, that of both ABA and GAs content increased with old stratification days. Effects of cold stratification on both GR and GP were significant (p < 0.05), which play an important role in releaving of seed germination and improving seed germination. The GR and GP were significantly negatively correlated with the contents of ABA and GA1/3, and positively correlated with the following iPAs, ZRs/ABA, iPAs/ABA. Introduction Cornus walteri Wanger. (Cornaceae) is a deciduous tree which mainly grows in the valley areas and hills of Korea and China (Lee et al. 2017). In Chinese traditional medicine, fruits and leaves of C. walteri have been widely utilized for the alleviation of skin inflammatory symptoms and the treatment of glycosuria (Kim et al. 2011, Kim et al. 2013, Park et al. 2016). Moreover, C. walteri is a woody oil tree, with very high oil contents in fruits (Paul and Don 2005), so the application and cultivation of this species has a rapid expansion in China recently. Tradditionly the breeding method of C. walteri is sowing, but the germination rate is very low without treatment before hand, which is usually a serious hurdle for production of the desired quantity of seedlings in nurseries (Kang et al. 2012). An understanding of seed dormancy mechanisms can be helpful in optimizing the distribution of seed germination in time or space (Nasreen et al. 2002). According to research there are some factors controlling seed germination and dormancy, including plant hormones, which are produced by both plant and soil bacteria, and interactions between plant hormones and plant genes affect seed germination (Miransari and Smith 2014). Research showed that hormones are the primary factors to cause seed dormancy, and ABA is the endogenous inhibitor of seed dormancy, and both GA and IAA are the corresponding germinating promoters (Carr 2009). Some scholars have also suggested that seed dormancy and germination depend on the balance between endogenous growth inhibitors and growth hormone agents (Wang et al. 2007). The studies regarding seed dormancy on C. walteri previously have been reported (Paul and Don 2005, Svendsen et al. 2007, Karen, et al. 2014), but relative mechanism has not yet been determined. Hence, further investigations on understanding possible responses, adaptations and physiological mechanisms of C. walteri to limit seeds germination is required. Author for correspondence: <704020830@qq.com>. Department of Horticulture, Jinling Institute of Technology, Nanjing 210038, PR China. Nanjing Pearl Spring Garden Construction Co, Ltd., Nanjing 211805, PR China.