EFFECTS OF HYDROXAMIC ACIDS ON ELECTRON-TRANSPORT AND THEIR CELLULAR LOCATION IN CORN

DIMBOA, the main hydroxamic acid in maize and wheat, is found mainly a s a glucoside in intact maize plants; when the tissue is damaged a bet a-glucosidase releases DIMBOA from DIMBOA-glucoside. The effects of DI MBOA and its glucoside were studied in maize mitochondria and chloropl asts. DIMBOA reduced electron transport in both mitochondria and chlor oplasts with an ID50 of 1.8 and 1.2 mM, respectively. DIMBOA-glucoside had no inhibitory effect. The glucoside and the enzyme were both pres ent in mesophyll parenchyma protoplasts. When these protoplasts were f ractionated, DIMBOA-glucoside was found in the extravacuolar fraction, while the DIMBOA-beta-glucosidase was in the vacuole. This seems to b e an efficient mechanism to prevent aglycone toxicity in vivo.