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Mauricio Tejera (Walker Lab)

Date & Location: March 24, 2020, at 12p; Room 168 Plant Biology Building

Subject: A closer look at Switchgrass (Panicum virgatum L.) carbon fluxes; what goes where and when

Abstract: Switchgrass (Panicum virgatum L.) is a perennial C4 grass, widely considered as a bioenergy crop. While many of its desired features are related to their perennial lifecycle, the crosstalk between perennial (roots and rhizomes) and annual organs (stems and leaves) is poorly understood. I study this communication from a source-sink balance perspective; how rhizome reserves limit leaf-level photosynthesis and how this balance changes under different environmental conditions. I experimentally manipulated sink strength (rhizome reserve status) by exposing rhizomes to different storage temperature or no storage. Preliminary results showed plants grown from rhizomes stored at high temperatures had ~40% faster net CO2 assimilation (A) than plants grown rhizomes exposed to no storage (P < 0.001). They also had higher A efficiency at low CO2 levels and faster electron transport rate (ETR). Next, I will study how the imposed sink limitations affect the electron transport chain (ETR) and how different sucrose or sorbitol solutions alter this limitation on excised leaves of each treatment. Compared to C3, relatively little is known what limits C4 photosynthesis. Along with sink and drought limitations, I also study low temperature effects on switchgrass A and the contribution of photorespiration at low CO2 levels. Surprisingly, I found that at CO2 concentrations near the compensation point (~4 ppm CO2) higher O2 concentration promote higher ETR and no changes in A. Altogether, the upcoming results would help characterize C fluxes and photosynthetic limitations in C4 plants under different environmental conditions.

Speaker Lab: Dr. Berkley Walker