When wildfire smoke fills the air, health experts advise people to stay indoors to avoid inhaling harmful particles and gases. But what about trees and other plants that can’t escape the smoke? It turns out, they respond in a way similar to humans: some trees essentially “hold their breath” by closing their pores.
HOW PLANTS BREATHE
Plants have tiny pores on their leaves called stomata. These pores function similarly to our mouths but with a key difference: while humans inhale oxygen and exhale carbon dioxide, plants do the opposite, taking in carbon dioxide and releasing oxygen. However, just like humans, plants also inhale and exhale other chemicals from the atmosphere. Unlike us, leaves breathe in and out simultaneously, constantly exchanging gases with their environment.
HISTORICAL CLUES: OVER A CENTURY OF RESEARCH
In the early 1900s, scientists observed trees in heavily polluted areas and found that those exposed to coal-burning pollution had black granules clogging their stomata. These granules were partly produced by the trees themselves. However, due to limited technology at the time, the chemical composition of these granules and their effects on photosynthesis remained unexplored.
Modern research has mostly focused on how wildfire smoke affects crops, with mixed results. For example, studies in California showed that smoke could scatter light in a way that enhanced photosynthesis and growth. However, lab studies exposing plants to artificial smoke indicated a drop in plant productivity during and after smoke exposure, though the plants did recover after a few hours.
THE TOXICITY OF SMOKE: A CHEMICAL REACTION
Wildfire smoke becomes more toxic as it travels long distances, undergoing chemical changes when exposed to sunlight. This process creates ground-level ozone, which can cause breathing problems in humans and damage plants by degrading leaf surfaces, oxidizing plant tissue, and slowing photosynthesis. Other compounds, like nitrogen oxides, can also harm plants by reducing photosynthesis.
While urban areas are typically seen as major sources of ozone affecting crops downwind, wildfire smoke is becoming an emerging concern. The interaction between wildfire smoke and plants is not yet fully understood, largely because studying smoke effects on living plants in the wild is challenging due to the unpredictability and danger of wildfires.
THEORIES BEHIND THE PLANT RESPONSE
Several processes might cause leaves to close their stomata in response to smoke:
- Coating of Leaves: Smoke particles could form a layer on the leaves, preventing the stomata from opening.
- Clogging of Stomata: Smoke could enter the leaves and physically clog the pores, making them sticky and unable to open.
- Physical Response: The leaves might detect the smoke and close their stomata preemptively to minimize damage.
It’s likely that a combination of these factors is at play, but the exact mechanisms are still unclear.
LONG-TERM IMPACT: AN UNCERTAIN FUTURE
The long-term effects of wildfire smoke on plants, including trees and crops, remain uncertain. With wildfires becoming more frequent and severe due to climate change, forest management policies, and human behaviour, understanding how smoke affects plant life is increasingly important.
The potential for repeated smoke exposure to have lasting impacts on plants is a pressing concern. As we continue to experience more intense wildfire seasons, it’s crucial to deepen our understanding of these effects to inform future forest management and agricultural practices.
Wildfire smoke doesn’t just affect air quality for humans; it also has significant implications for plant life. Trees and other plants may respond to smoke by closing their stomata and shutting down their gas exchange, essentially “holding their breath.” While this response might help them survive short-term exposure, the long-term consequences are still unknown. As wildfires become more common, studying these impacts will be essential for preserving both natural ecosystems and agricultural productivity.
