2019 ASHS Annual Conference

Postharvest needle abscission poses a challenge to the balsam fir (Abies balsameaL.) Christmas tree industry. Literature on the topic has identified numerous causes for needle abscission, such as water deficit, hormonal signals, genotypic variance, and lipid composition changes. However, this experiment focused specifically on changes in stomatal conductance. Stomatal conductance is the rate of transpiration through the stomates and dictates water uptake. Manipulating stomatal conductance could affect needle abscission by increasing or decreasing water uptake, which in turn could affect water status. This study explored this concept through manipulation of balsam fir stomata by several chemical treatments (ABA, fluoridone, BAP, theophylline, potassium nitrate, and dopamine) to determine if any of these compounds had an impact on water uptake, moisture content, and needle abscission. Stomatal conductance decreased by 43% after application of ABA and increased by 28% after application of potassium nitrate. Consequently, the ABA treatment resulted in significantly slower moisture loss while potassium nitrate resulted in significantly higher moisture loss. Despite changes in stomatal conductance and moisture loss, there were no significant changes on needle retention. Needle abscission commenced after an average of 12.5 days and reach 100% completion after an average of 71.9 days. It is possible to manipulate stomatal conductance and water uptake through chemical methods, but this alone is not enough to guarantee superior needle retention. It is proposed that perhaps other chemical signals resulting from root detachment play a critical role in postharvest needle abscission.