Flowering dogwood (C. florida L.), a member of the subgenus Benthamidia in Cornus, is a small- to medium-sized deciduous tree native to eastern North America (Borer et al., 2013; McLemore, 1990; Rushforth, 1999). The species is prized for the ornamental value of the pink, red, or white petal like, enlarged bracts in early spring, and brilliant red foliage and bright red berries in autumn. As noted by the U.S. Department of Agriculture Census of Horticultural Specialties (USDA-NASS, 2010) from retail and wholesale sales, in the United States, and especially in states such as Tennessee, C. florida is an economically important ornamental tree and may also be used as an important food source for wildlife in forests when its fruits ripen in autumn (Paul and David, 2008; Stiles, 1980). In addition, C. florida is widely considered as a calcium pump, increasing the rates of mineralization of the forest litter and soil because of the high calcium concentrations in its foliage (Holzmueller et al., 2007; Thomas, 1969).
Typically, C. florida is propagated from seeds, but the seeds usually develop strong dormancy (Coartney et al., 1989), which may be a great challenge for seed reproduction (Dirr and Heuser, 1987). Studied with C. kousa var. Chinensis, Fu et al. (2013) indicated that the dormancy of chinese dogwood could be classified as physiological dormancy due to the existence of inhibitory substances in the endosperm. However, the causes of C. florida seed dormancy remains largely unknown thus far, except that Laufmann and Wiesner (1998) reported rapid germination of eastern dogwood (C. florida cv. Small) by embryo extraction, cut cotyledons, and GA3. Normal seed germination of C. florida requires a moist prechill treatment at 3–5 °C for 3–4 months. In this study, we aimed to identify the multifaceted causes and to establish a practical and powerful method to successfully break the seed dormancy of C. florida that can be applied in seed reproduction practice.
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