ACTIVATION OF GLYOXYLATE CYCLE ENZYMES IN CUCUMBER FRUITS EXPOSED TO CO2

Cucumber fruits exposed to a 60% CO2 environment for 3 d at 20 degrees C showed a higher respiration rate, a lower respiratory quotient, and lower levels of malate, citrate+ isocitrate, and glyoxylate than did control fruits. Moreover, in the CO2 treatment, fumarate and succinate increased dramatically on the first day and after the second day, res pectively, while 2-oxoglutarate showed a temporary increase on the fir st day and a subsequent decrease. Isocitrate lyase and malate synthase activity tended to increase throughout the experimental period of the CO2 treatment. These results appear to point to a rapid operation of glyoxylate cycle due to high CO2.