Influence of storage, temperature, and light on germination of Japanese brome seed

Abstract

Japanese brome (Bromus japonicus Thunb.), an alien annual grass, is an important component of some northern mixed-prairie communities. Understanding the relationship between environment and population dynamics for this species is critical for efficient management of infested ranges. Our objective was to determine the germination pattern of seed harvested in the Great Plains with varying collection dates, storage conditions, incubation temperatures, and light regimes. Seeds were collected from inflorescences (nondisseminated seed) during July in Oklahoma a Montana and during November and December in Montana. July collections were stored in paper sacks in a laboratory, and November and December collections were divided into thirds and stored in an unheated warehouse, oven-dried at 46 degrees C, or frozen at -18 degrees C. Seeds were germinated in 2 regimes, where temperatures alternated every 12 hours and light was provided during the hours of high temperature. One regime provided 10 days of prechilling (0 and 10 degrees C) followed by 18 days of a warm temperature (8 and 23 degrees C) (chilling). Another regime consisted of 28 days of the warm temperature (warm). Samples of seeds were also imbibed in the warm regime with 12-hour or intermittent periods of light. July collections germinated rapidly to > 90% regardless of temperature. November and December collections stored in the warehouse germinated > 70% in the warm regime, but germination was reduced to < 20% with chilling, suggesting secondary dormancy was induced by imbibition at 0 degrees C. Oven drying was the only treatment that consistently reduced maximum germination. Darkness enhanced 7-day germination, but light improved 28-day germination, and more recently collected seeds were more sensitive to light than older ones. These and earlier findings from Kentucky suggest Japanese brome seeds grown in different locations respond similarly to changing environmental conditions.