Ethylene triggers needle abscission in root-detached balsam fir

Abstract

Post-harvest needle abscission is a major challenge for Christmas tree and greenery industries. It was hypothesized that ethylene triggers abscission in balsam fir. Three experiments were conducted to test this hypothesis. In experiment 1, 70 balsam fir branches were collected, placed in water, and ethylene evolution was observed over time. In experiment 2, a 2 9 5 factorial experiment was designed to determine the effect of exogenous ethylene and an ethylene receptor blocker, 1-methylcyclopropene (1- MCP), on needle abscission. In experiment 3, a 2 9 6 factorial experiment was designed to determine the effect of exogenous ethylene and an ethylene inhibitor, amino- ethoxyvinylglycine (AVG), on needle abscission. It was found that ethylene evolution was the highest 1-2 days prior to needle abscission, which was consistent in untreated branches and branches exposed to exogenous ethylene. Exposure to exogenous ethylene significantly decreased needle retention by 63%. When ethylene receptors were blocked by 1-MCP, needle retention increased by 147% despite the presence of ethylene and increased by 73% in the absence of ethylene when com- pared to the respective controls. When endogenous ethyl- ene synthesis was inhibited by AVG, there was no improvement in needle retention in the presence of ethyl- ene, but there was a 113% increase in needle retention in the absence of exogenous ethylene. Ethylene is strongly implicated as the signal triggering abscission in root- detached balsam fir.