Role of Light Emitting Diode (LED) In Negating Needle Drop In Balsam Fir (Abies balsamea, L)

Balsam fir (Abies balsamea, L) is the principle Christmas tree species grown in Atlantic Canada.  It is preferred by consumers for its unique fragrance as well as its soft needle characteristics.  In Atlantic Canada, the industry is valued at approximately $72 million annually.  However, early harvesting practices, in combination with the occurrence of warm fall temperatures in late October, are suspected to have severely deteriorated the needle retention qualities of Balsam fir.  Light has a significant role in altering the growth and development of plants. This includes negating senescence as leaves kept in the dark, senesce faster compared to the ones that are exposed to light.  There is no information relating to the role of various LED spectrums on needle senescence and abscission in balsam fir.  If any of the LED spectrums could provide a control, then this would allow the use of LED technology to illuminate each of the trees post harvest, through shipment or at home to control needle loss.  The objective of the experiment was to expose balsam fir branches to various spectrums of LED lights at various time exposures.  Two year old branches were collected from Tree Breeding Centre, Department of Natural Resources, Debert, NS (45º 25’ N, 63º 28’ W).  Branches were placed in custom built chambers that contain LEDs emitting red, blue and white spectrum.  Control treatments were exposed to normal growth chamber lights and a dark treatment was included.  Branches were left in the chambers at 1, 4, 8, 12, 24 and 48 hours and after exposure were returned to growth chamber conditions.  Branches were monitored for water use and needle loss daily.  Branches expose to red and white lights at the 12 hour exposure had significantly higher needle retention days (NRD) than other treatments.  NRD for red and white treatments were between 65 to 75 days compared to the 50 to 55 days for the other treatments.  There was little difference in NRD at the 1, 4 or 8 hour exposures for any spectrum.  Overall, the red and white spectrums tend to have more of an effect on NRD at the 12, 24 and 48 hour exposures.