Participating Students - Jessica Cruz de Osuna

Jessica Cruz de Osuna
University of California, Berkeley
BART Enrollment Year: 2004
Email Address: jessicalosuna at
Atmospheric Mentor: Inez Fung, UC-Berkeley
Biosphere Mentor: Dennis Baldocchi, UC-Berkeley

Research Topics
Mesophyll Conductance as a limiting factor of photosynthesis in a northern hardwood forest and mediterranean savannah: Recently, it has been shown that mesophyll conductance plays an important role in determining the rate of photosynthesis in C3 leaves, and should not be left out of leaf photosynthesis models (Ethier & Livingston 2004). Mesophyll conductance (gm) occurs when a difference exists between the partial pressure of CO2 in the intercellular space (ci) and at the site of carboxylation (cc). This research proposes to measure cc and gm in oak and maple through techniques utilizing stable carbon isotopes and electron transport. This research also seeks to determine the effects of changes in atmospheric CO2 and climate on cc and gm through utilizing open-top chambers already in place at the University of Michigan Biological Station, and by setting up similar chambers near Ione, CA in the lower foothills of the Sierra Nevada Mountains. This research will contribute to the improvement of the multilayer biophysical CANOAK model developed by Dennis Baldocchi. A greater understanding of mesophyll conductance and its response to atmospheric changes will allow for better modeling of photosynthesis in future climatic condit ions. As CO2 in the atmosphere increases, it is important to be able to quantify how much excess CO2 in the atmosphere will be compensated by an increase in the sink from forests. Understanding mesophyll conductance will also deepen our understanding of the carbon cycle, and the interactions with the atmosphere driving this cycle.

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