Determining the Link Between Certain Hydraulic Properties and Postharvest Needle Abscission in Balsam Fir (Abies balsamea (L.) Mill.)

Abstract

The goal of this project was to better understand the link between certain hydraulic properties and postharvest needle abscission (PNA) in balsam fir. Balsam fir branches were kept under various conditions to measure and manipulate stomatal conductance and water use over time. Following harvest, water use sharply declined, though a lack of significant xylem blockage progress over time suggests that xylem blockage may not be the cause for PNA. Stomatal conductance also declined postharvest, showing that the decrease in water use may be due to stomatal closure. Keeping branches under high light intensity and high humidity promoted stomatal conductance, while simulating root pressure in a postharvest situation resulted in a significant improvement in stomatal conductance and promoting needle retention. Results of these experiments suggest that lack of root pressure may be a biophysical trigger for needle abscission, possibly by signaling a closure of the stomata.