Effects of Ultraviolet Radiation on the Brown Midrib Mutation in Sorghum Bicolor and Zea Mays

Identification of feedstock for cellulosic ethanol is important if the Federal Biofuels Mandate for displacing 30% of petroleum consumption by 2030 is to be met. Ideally, feedstock should contain high amounts of structural carbohydrates while maintaining low concentrations of lignin in the cell walls of plants. The Brown Midrib (BMR) mutation in Sorghum bicolor (sorghum) and Zea mays (corn) have been proffered as potential candidates because they have lowered expression of cinnamyl alcohol dehydrogenase and caffeic O-methyl transferase enzymes involved in lignin production. However, the precursors of lignin are important in absorbing potentially-damaging ultraviolet (UV) radiation in the epidermis of plants. We examined how UV influenced production of UV-screening compounds, chlorophyll fluorescence, growth and cell wall constituents in BMR- corn and -sorghum. Plants were grown in a UV-transparent greenhouse under filters that either attenuate (mylar) or transmit (aclar) ambient UV. Over the course of 57 days we examined epidermal screening of UV with a pulse-amplitude modulated fluorometer and the quantum yield of photosystem II (PSII) electron transfer (15% taller. It appears that the BMR mutation may potentially compromise the UV-screening ability of these plants and could potentially impact theoretical ethanol yield