A gender comparison of corticular photosynthesis in Populus tremuloides using CO2 efflux rates and C13.

Abstract

In Populus tremuloides, photosynthesis has been observed in the bark, termed corticular photosynthesis. Various differences have also been observed across gender, such as higher water-use efficiency (WUE) in male Acer negundo, and greater long term clonal growth in female P. tremuloides. In this research, I used an isotopic analysis of photosynthesis and WUE to make correlations in differences across the clones. We used a LI-6400 (Li-Cor Inc., Lincoln, Nebraska) to measure photosynthetic rates of excised P. tremuloides under varying light levels, and could therefore deduce photosynthetic rates. Gas samples of twig respiration under full light and no light were analyzed using an Isotope Ratio Mass Spectrometer (IRMS). From this, we found the carbon isotope fractionation that occurs during corticular photosynthesis. Specific leaf area and carbon isotope ratios of leaf tissue were used to determine WUE. We found no gender correlation in WUE, rate of corticular photosysntesis, or C13 discrimination. It is suspected that there may be a gender correlation in proportional refixation, however these results are inconclusive. Variability in this research is attributed to the uncontrollable variables such as moisture content, age, and height of the sample.