Short‐term effect of elevated CO (2) concentration (0.5%) on mitochondria in diploid and tetraploid black locust (Robinia pseudoacacia L.)

Recent increases in atmospheric CO (2) concentration have affected the growth and physiology of plants. In this study, plants were grown with 0.5% CO (2) for 0, 3, and 6 days. The anatomy, fluorescence intensity of H(2)O(2), respiration rate, and antioxidant activities of the mitochondria were analyzed in diploid (2×) and tetraploid (4×) black locust (Robinia pseudoacacia L.). Exposure to 0.5% CO (2) resulted in clear structural alterations and stomatal closure in the mitochondria. Reduced membrane integrity and increased structural damage were observed in 2× plants at 6 days. However, after 0.5% CO (2) treatment, little structural damage was observed in 4× plants. Under severe stress, H(2)O(2) and malondialdehyde were dramatically induced in both 2× and 4× plants. Proline remains unchanged at an elevated CO (2) concentration in 4× plants. Moreover, the total respiration and alternative respiration rates decreased in both 2× and 4× plants. In contrast, the cytochrome pathway showed no decrease in 2× plants and even increased slightly in 4× plants. The antioxidant enzymes and nonenzymatic antioxidants, which are related to the ascorbate–glutathione pathway, were inhibited following CO (2) exposure. These analyses indicated that 4× and 2× plants were damaged by 0.5% CO (2) but the former were more resistant than the latter, and this may be due to increases in antioxidant enzymes and nonenzymatic antioxidants and stabilized membrane structure.