Effects of Temperature and Presowing Treatments on Showy Menodora Seed Germination

Abstract

Low seed germination is a problem in establishment of showy menodora (Menodora longiflora Gray). Objectives of this study were to determine the effects of temperature, light, and presowing treatments on showy menodora germination. Scarified and untreated seeds were germinated at 5/15, 10/20, 15/25, 20/30, 25/35, and 30/40 degrees C (12 hour/12 hour) with 12 hours of light at the warmer temperature or complete darkness. Seeds were subjected to: (1) chemical scarification with concentrated (18.0 mol liter-1) H2 SO4, 2.9 mol liter-1 H2O2, or 0.7 mol liter-1 NaOCl, (2) a hot (80 degrees C) water soak, and (3) nicking with a razor blade. Percent germination and germination rate were highest at 20/30 degrees C. The highest percentage of abnormal seedlings occurred for mechanically scarified seeds at 5/15 degrees C. Light did not affect germination at 15/25, 20/30, and 30/40 degrees C, but enhanced germination at 5/15, 10/20, and 25/35 degrees C. Scarification enhanced percent germination and germination rate at all temperatures. At 20/30 degrees C, nicking seeds with a razor and a 3-minute soak in 0.7 mol liter-1 NaOCL resulted in 81 and 78% germination, respectively, of 1-year-old seeds, compared to 53% for untreated seeds. These results indicate that showy menodora seeds should be scarified by mechanical means or with 0.7 mol liter-1 NaOCL and planted when average daily minimum/maximum soil temperatures are about 20/30 degrees C for maximum germination.