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Harvard Forest Symposium Abstract 2018

  • Title: The relationship between water potential and phloem loading in Quercus rubra
  • Primary Author: Jessica Gersony (Not specified)
  • Additional Authors: Uri Hochberg (Not specified); Michele Holbrook (Harvard University); Fulton Rockwell (Harvard University)
  • Abstract:

    Red oaks are canopy dominant trees that have high rates of photosynthesis and thus also high transpiration rates. As a result of the latter, red oak exhibits large diurnal fluctuations in leaf water potential. Because low water potentials should impede the build up of phloem pressures necessary to move sugars out of leaves, we asked when over the diurnal cycle are carbohydrates exported from leaves. We measured diurnal net assimilation, leaf water potential, starch and soluble sugar patterns, organic metabolite concentrations and change in weight over time to elucidate the relationship between diurnal water potential and carbon export from the mesophyll to the phloem for five Quercus rubra trees at Harvard Forest in Petersham, Massachusetts. The results were not what we expected. Future work will explore how the carbohydrate export patterns we observed occur in a species that has been characterized as a passive loader.

  • Research Category: Physiological Ecology, Population Dynamics, and Species Interactions