Effects of Cinnamon Acid on Respiratory Rate and Its Related Enzymes Activity in Roots of Seedlings of Malus hupehensis Rehd

This paper studied the effects of cinnamon acid treatments on the respiratory rate and related enzymes activity in the seedling roots of Malus hupehensis Rehd. It would provide information for understanding the mechanisms of inhibition damage caused by continuous cultivation of apple tree. 20 mL of solution containing different concentrations of cinnamon acid was added into container with the tested seedlings. After treatment, the samples were taken periodically and the respiratory rates were measured by OXY-LAB oxygen electrodes under 25°C stable temperature and then the activities of related enzymes were measured. The rates of total respiration and other 2 pathways [tricarboxylic acid cycle (TCA) and pentose phosphate pathway (PPP)] appeared initially an increasing treads and late (on the 3rd d) began to decline. However, they again appeared an increase trend at the end period, on the contrast, the respiratory rate of embden-meyer-hot-parnas (EMP) pathway appeared a stead decline tread but it had a recover on the last day. The respiratory rate of total and 3 pathways were decreased under 125 mg kg−1 (soil). The dynamic trends of the enzymes activities of pyrophosphate-dependent phosphofructokinase (PFK), glucose-6-phosphate dehydrogenase (G-6-PDH) and malate dehydrogenase (MDH) showed similarly. In conclusion, treatments of certain concentration of cinnamon acid would inhibit the respiratory rate and related enzymes activity of roots of M. hupehensis Rehd. And the inhibition degrees were positively related with concentration of cinnamon acid treatments.