Abstract Detail

Physiology

Hull, Ashley [1], Neufeld, Howard [2].

IMPACTS OF NEEDLE AGE AND TREE ARCHITECTURE ON PHOTOSYNTHETIC PHYSIOLOGY OF FRASER FIR (Abies fraseri) CHRISTMAS TREES.

Fraser fir (Abies fraseri) Christmas trees contribute approximately $100 million to the economy of western NC annually. Unlike A. fraseri growing in their endemic, high elevation habitat of the Southern Appalachian Mountains, commercially grown varieties are trimmed annually to create the classic Christmas tree-like canopy. Such trees have denser canopies than their native counterparts, but little is known about how changes in tree architecture affect carbon assimilation. We studied light interception and photosynthetic characteristics of three needle age classes (current, 1, and 2 yr old) on 2 m tall farm-grown Fraser fir trees near Boone, NC. We hypothesized that gas exchange would decline due to aging, but also because of declines in light penetration by the dense canopy. We measured light depletion at three canopy depths using a Li-1500 Quantum Sensor Logger, light response curves on detached planar needles and on twigs with naturally oriented needles using an Li-6800 gas exchange system, and chlorophyll, minimum stomatal conductances, and epicuticular wax content. Direct light intensity on a sunny day near noon was ~2000 µmol m-2 s-1 for current year needles but decreased to just 3% and 1% at typical canopy locations for 1 and 2 yr old needles, respectively. Apparent quantum efficiency, maximum photosynthesis, and light saturation were lowest in 2 yr old planar needles, while dark respiration, maximum photosynthesis, and light saturation were lower in 1 yr old twigs. Chlorophyll was highest in 2 yr old needles, while minimum stomatal conductances and epicuticular wax content did not differ among needle age classes. A decreased light environment, high chlorophyll, and low photosynthetic rates in 2 yr old needles indicate the need for further research to determine why older needles are retained inside the tree canopy given their low or even negative contribution to the carbon budget of these trees.

1 - 331 W Coventry Dr, Franklin, NC, 28734, United States
2 - Appalachian State University, Biology, 572 Rivers St., Boone, NC, 28608, United States

Keywords:
physiology
agriculture
Trees
Fir
Fraser fir
high altitude plant
climate change
Endemic Species
Commercial
photosynthesis
Needle Age
Tree Architecture.

Presentation Type: Oral Paper
Number: PHYS1004
Abstract ID:354
Candidate for Awards:None