How Cherry Blossoms React to Increased Ozone: Health and Emissions

Jenn Hoskins
20th July, 2024

How Cherry Blossoms React to Increased Ozone: Health and Emissions

Image Source: Natural Science News, 2024

Key Findings

  • The study from the University of Seoul found that elevated ozone (E-O3) initially stimulated Prunus × yedoensis seedlings, a phenomenon known as hormesis
  • Prolonged E-O3 exposure led to significant declines in photosynthetic efficiency, pigment content, and cellular integrity in the seedlings
  • Elevated O3 levels caused structural changes in leaf cells, including cell wall thickening and chloroplast damage, indicating severe oxidative stress
Ozone (O3) absorption through leaf stomata disrupts plant physiological processes, prompting various defense mechanisms to mitigate O3-induced harm. This study from the University of Seoul[1] measured parameters including cell structure, gas exchange, carbon assimilation, lipid peroxidation, and biogenic volatile organic compounds (BVOCs) emissions to evaluate the physiological impact of Prunus × yedoensis under elevated ozone (E-O3) exposure. The findings provide a comprehensive understanding of how O3 affects plant health and growth, particularly in urban environments where O3 levels can be high. The study observed that during the early phases of E-O3 exposure, the Prunus × yedoensis seedlings exhibited a slight stimulatory effect. This phenomenon, known as hormesis, indicates that low doses of a stressor can initially stimulate adaptive responses in plants[2]. However, once a specific threshold of E-O3 was exceeded, significant negative effects on photosynthetic parameters, pigment content, and antioxidant capacity were noted. This aligns with previous findings that low O3 concentrations can induce adaptive responses, but higher concentrations lead to adverse effects[2]. The research showed that after three weeks of E-O3 exposure, there were no significant differences in the appearance of leaf stomata under field emission scanning electron microscopy. However, significant ultrastructural changes were observed in the leaf mesophyll cells. These changes included grana degradation, membrane decomposition, cell wall thickening, wart-like protrusion formation, and increased plastoglobulus density within the chloroplasts. Such structural alterations indicate severe oxidative stress and cellular damage caused by elevated O3 levels. Chlorophyll content in the E-O3 group decreased by 38.71%, and solute leakage increased by 20.57%, indicating compromised cell integrity and function. The net photosynthetic rate was almost two times lower with E-O3 exposure, demonstrating a substantial decline in the plant's ability to assimilate carbon. Interestingly, there were no significant differences in stomatal conductance, suggesting that the primary damage occurs at the cellular and subcellular levels rather than through changes in stomatal behavior. One notable aspect of the study was the correlation between E-O3 and BVOCs emission rates. BVOCs, such as methanol, monoterpenes, and sesquiterpenes, play crucial roles in plant signaling and stress responses[3]. Under E-O3 conditions, the emission of these compounds was significantly altered. Previous research has shown that ozone fumigation can lead to a rapid decrease in monoterpene and sesquiterpene concentrations due to ozonolysis and reactions with OH radicals[3]. This study confirms that elevated O3 levels disrupt BVOC emissions, potentially affecting plant-plant and plant-insect communications. Additionally, the study's findings on cell wall thickening and wart-like protrusion formation are consistent with earlier observations in different plant species exposed to O3[4]. Such structural modifications are likely adaptive strategies to resist oxidative damage. However, the overall negative impact on photosynthesis and cell integrity suggests that these adaptations are not sufficient to counteract the detrimental effects of prolonged E-O3 exposure. In conclusion, this study from the University of Seoul demonstrates that elevated ozone levels can initially induce a hormetic stimulatory effect in Prunus × yedoensis seedlings. However, once a critical threshold is exceeded, O3 exposure adversely affects the plant's physiology, leading to significant declines in photosynthetic efficiency, pigment content, and cellular integrity. The research highlights the need for continuous management of O3 phytotoxicity in urban environments to safeguard the health and growth of woody plants.

EnvironmentBiochemPlant Science

References

Main Study

1) Korean flowering cherry (Prunus × yedoensis Matsum.) response to elevated ozone: physiological traits and biogenic volatile organic compounds emission

Published 19th July, 2024

https://doi.org/10.1007/s13580-024-00628-0

Related Studies

2) Predicting the effect of ozone on vegetation via linear non-threshold (LNT), threshold and hormetic dose-response models.

https://doi.org/10.1016/j.scitotenv.2018.08.264

3) The effect of ozone fumigation on the biogenic volatile organic compounds (BVOCs) emitted from Brassica napus above- and below-ground.

https://doi.org/10.1371/journal.pone.0208825

4) Ozone foliar symptoms in woody plant species assessed with ultrastructural and fluorescence analysis.

Journal: The New phytologist, Issue: Vol 166, Issue 3, Jun 2005


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