Impact of chronic elevated ozone exposure on photosynthetic traits and anti-oxidative defense responses of Leucaena leucocephala (Lam.) de wit tree under field conditions

In this study, the impact of long term exposure of elevated ozone (+20 ppb above ambient) on photosynthetic traits and anti-oxidative defense system of Leucaena leucocephala, a tree of great economic importance, was studied in a Free Air Ozone Concentration Enrichment (O-3-FACE) facility at different time intervals (6, 12, 18, and 24 months). Results showed that net photosynthesis, photosynthetic pigments and lipid peroxidation were significantly reduced after 6, 12 and 24 months of exposure to elevated ozone (eO(3)) whereas stomatal conductance and transpiration rate were significantly decreased after 12 months of exposure to eO(3). Antioxidant enzymatic activities (catalase, ascorbate peroxidase and glutathione reductase) were significantly increased after 12 months of exposure to eO(3). Ascorbate was increased significantly after 6 and 12 months of exposure to eO(3) while reduced glutathione content declined significantly after 6 and 24 months of exposure to eO(3). The study showed that there were several negative long lasting physiological and biochemical responses in Leucaena. The results provide evidence that Leucaena exhibited greater sensitivity to O-3 during initial exposure (up to 12 months) but showed moderate tolerance by the end of the 2nd year. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The study revealed that long-term exposure to elevated ozone levels had significant effects on the photosynthetic traits and anti-oxidative defense system of Leucaena leucocephala. While the tree initially showed greater sensitivity to ozone during the first 12 months, it developed moderate tolerance by the end of the second year.