2017 ASHS Annual Conference

Postharvest needle abscission is a serious threat to balsam fir Christmas tree industry. Baling of trees have been shown to negatively contribute to postharvest needle abscission however, exposure of trees to low temperature or cold acclimation has also been shown to delay needle abscission. In this study, we tested the hypothesis that low temperature can over-ride the negative effect of the mechanical stress caused by tree baling. A bale of six-year-old trees in groups of 3 and non-baled trees were exposed to varying temperatures of 5, 10, 20, or 30°C for 30 days while the control trees was kept outside the laboratory at ambient temperature that ranged from 2°C to 3°C. After that, trees were transferred to 5L jars containing 3L water until a minimum of 60% needle loss was achieved. Trees were observed for percent needle loss PNL (%), needle retention duration (NRD), average water use (AWU), ethylene and volatile terpene compound (VTC) evolution. The absolute control (non-baled trees) irrespective of the storage temperature, the needles were lost within 14 days of storage primarily through discoloration. Trees stored at 20°C and 30°C lasted for a duration of 7 and 14 days at significantly higher humidity of 83% and 85%, respectively. Our results also show that postharvest storage of trees under varying temperatures (3.2, 5°C and 10°C) strongly mitigate NRD through its effect on AWU, ethylene and VTC evolutions. At lower temperature (<5^oC), tree had higher AWU, high NRD, high ethylene and VTC evolution. This suggests the ability of trees to take up water as depicted in high AWU, and can be beneficial to balsam fir trees by slowing down needle abscission, despite an increase in ethylene and VTC suggesting the negative effects of baling, ethylene and VTC can be overcome by low temperature storage.