Switchgrass Responses to Manganese Availability.

Manganese (Mn) is an essential micronutrient and has a broad range of functions. Manganese plays a key role in photosynthetic processes, including as a cofactor for the NAD malic enzyme (NAD-ME) which releases CO₂ from malate transported from mesophyll cells into bundle sheath cells in the NAD-ME subset of C4 plants.   As a perennial bioenergy feedstock, switchgrass (Panicum variegatum L.), a NAD-ME type C4 plant, is considered a promising species for sustainable production of large amounts of bio-based fuel.  Since only limited information is available on the Mn requirement of switchgrass, the objective of this study was to characterize the response of switchgrass photosynthesis and biomass production to Mn availability.  Two switchgrass genotypes, Alamo and Cave-in-Rock, were grown hydroponically with Mn concentrations ranging from 0 to 100 µM.   and in pots under field conditions.  Total biomass of hydroponically grown plants increased with increasing Mn concentration in both switchgrass genotypes.  Ongoing out-door experiments with switchgrass grown in pots are being conducted to examine photosynthetic characteristics in response to different Mn treatments under field conditions.  Results from these experiments will be presented and discussed