EFFECTS OF ROOT EXUDATE SORGOLEONE ON PHOTOSYNTHESIS

The aim of this investigation was to determine if sorgoleone (SGL), a p-benzoquinone in Sorghum bicolor root exudate, is a photosynthesis inhibitor. Assays using Glycine max leaf disks showed concentrations as low as 10 muM SGL inhibited oxygen evolution more than 50%. Tests conducted on chloroplasts isolated from Pisum sativum showed that SGL is a powerful inhibitor of CO2-dependent oxygen evolution. Using a chloroplast suspension equivalent to 80-100 mug chlorophyll, the I50 was approximately 0.2 muM SGL. These data indicate inhibition of photosynthesis is part of the explanation for growth reduction caused by this allelochemical.