Photosynthesis and rhizome carbohydrate concentrations of switchgrass grown from reserve-depleted rhizomes

A long-standing question in perennial grass breeding and physiology is whether yield improvement strategies could compromise winter survival. Perennial grasses rely on the pool of carbohydrates accumulated in storage organs from the previous growing season for winter maintenance and spring regrowth. Yield improvement strategies could reduce winter survival if they increase biomass and grain yields at the expense of carbon allocation to storage. Therefore, it is crucial to better understand the dependence of regrowth on storage reserves. We experimentally depleted switchgrass (Panicum virgatum L.) rhizome reserves by storing rhizomes for two weeks at 5 °C (control treatment) and 25 °C (reserve-depleted treatment). During the storage period rhizome respiration was 5.3x higher at 25 °C (0.010 μmol CO2 g-1 min-1 at 5 °C vs. 0.054 μmolCO2 g-1 min-1 at 25 °C; P < 0.0001) and the starch content was depleted by 30% by the end of storage. Surprisingly, reserve-depleted switchgrass had 60 % la...