Effect of Pre-Treatments on Dormancy of Goldenrain-Tree (Koelreuteria paniculata Laxm.) Seeds

Goldenrain-tree (Koelreuteria paniculata Laxm.) is wide spread as an ornamental tree but the propagation is difficult because of pronounced seed dormancy. Unscarified seeds of K. paniculata Laxm. failed to germinate after any pre-treatments. Similarly, seeds soaked or soaked and redried without chilling were unable to germinate. However, seeds that were scarified, without soaking or soaking-redrying, gave 44% germination after 60 days of moist chilling. The germination was increased to more than 50% when seeds were soaked or soaked-redried in DW or GA for 5 h and moist chilled for 60 days (DW) and 30 days (GA). On the other hand, the germination of seeds soaked for 24 h and moist chilled was very low, but was higher if the seeds were redried after soaking. Dry chilling after soaking or soaking-redrying for 24 h also promoted germination, and maximum germination (> 50%) was achieved after 15 days of dry chilling. In general, higher germination was associated with higher germination rate, i.e., faster germination, except dry chilled seeds that were slow to germinate despite their higher germination. These results clearly indicated that K. paniculata seeds had both exogenous and endogenous dormancy and identified some treatments that released the dormancy.