Poster Session # 15: Plant Ecology.

Wednesday, August 6 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.

Diurnal changes in nitrogen uptake and root respiration in loblolly pine seedlings.

Lucash, Melissa*,1, Scholberg, Johannes2, Yanai, Ruth1, 1 SUNY-ESF, Syracuse, NY2 University of Florida, Gainesville, FL

ABSTRACT- Although energy derived from root respiration can be utilized for nitrogen uptake, few studies have simultaneously measured root respiration and N uptake. In this study, root respiration and N uptake were simultaneously measured in loblolly pine seedlings grown in soil-uptake-monitoring (SUM) columns filled with sand. To determine how the supply of photosynthate affects preference for NO3- or NH4+, N uptake was measured under both light and dark conditions. N uptake was measured by filling columns with a known volume and concentration of nutrient solution. After 2hrs, the solution was removed by a vacuum pump and analyzed for NO3- and NH4+. During the uptake measurements, root respiration was measured in the column headspace using a LI-COR 6400. The measurements were repeated using a range of N concentrations.

Key words: uptake, respiration, Pinus taeda, nitrogen