GERMINATION REQUIREMENTS OF METROSIDEROS-POLYMORPHA, THE DOMINANT TREE OF HAWAIIAN LAVA FLOWS AND RAIN-FORESTS

Experiments were performed to determine the effects of burial, light quality, and temperature on seed germination of Metrosideros polymorpha, the dominant tree of Hawaiian lava flows and rain forests. Fewer than 1 percent of seeds buried under 5 mm of sand were able to germinate and emerge, compared to 90 percent for seeds sown on the sand surface. Germination was greater under white, red, or far-red light (all greater-than-or-equal-to 62%) than in the dark (less-than-or-equal-to 10%). The light requirement was not overcome by a fluctuating thermoperiod (of 5-degrees/15-degrees-C or 15-degrees/25-degrees-C). Seeds germinated in all constant-temperature treatments (10-degrees to 34-degrees-C). Germination percent and rate (pace) were highest at 22-degrees-C and lowest at 34-degrees-C. There were intraspecific differences between seeds from pubescent and glabrous parents, with seeds from pubescent plants germinating in slightly higher numbers at high temperatures, and slightly faster in many treatments. The results suggest that M. polymorpha seeds are capable of germinating rapidly under a wide variety of environmental conditions, and are unlikely to form a persistent soil seed bank.