Breaking combinational dormancy of Rhus javanica L. seeds in South Korea: Effect of mechanical scarification and cold-moist stratification

Abstract

Seeds with combinational dormancy have both physical (PY) and physiological (PD) dormancy. Chemical scarification and cold-moist stratification alleviate PY and PD, respectively. Therefore, we tested the effectiveness of mechanical scarification and cold-moist stratification for the release of combinational dormancy in Rhus javanica seeds to minimize the possibility of any internal damage and determine the optimal germination conditions. Mechanical scarification by a brushing machine and cold-moist stratification for 12 weeks weakened the pericarp and improved water absorption and percent germination. Prolonging mechanical scarification for up to 20 min further improved water absorption and percent germination; however, there was no significant difference in germination after 20 min (64.9%) and 40 min (63.1%) of mechanical scarification. The removal of blister-like structures in nontreated seeds by mechanical scarification enhanced water absorption. Further, cracks between the two inner pericarp cell-layers improved water absorption. Combined mechanical scarification (20 min) and cold-moist stratification (12 weeks) effectively broke combinational dormancy of R. javanica seeds and, therefore, comprise a suitable treatment for seed germination.