Atmospheric Lead Deposition under Climate Change: Implications for Lettuce Yield and Dietary Exposure Risks.

Area of Science:

• Environmental Science
• Plant Biology
• Toxicology

Background:

• Recurrent heatwaves (HW) and fine particulate matter lead (PM2.5-Pb) pose significant threats to agriculture and food safety.
• The combined mechanistic impacts of HW and PM2.5-Pb coexposure on crops remain largely unknown.

Purpose of the Study:

• To investigate the combined effects of heatwaves and PM2.5-Pb coexposure on lettuce (Lactuca sativa L.) physiology, metabolism, and nutritional quality.
• To elucidate the underlying mechanisms driving yield collapse and altered nutritional profiles.

Main Methods:

• Lettuce was exposed to simulated heatwaves and PM2.5-Pb.
• Physiological parameters (biomass, photosynthesis, stomatal conductance) were measured.
• Metabolomics analysis was performed to identify metabolic shifts.
• Simulated gastrointestinal models were used to assess lead bioavailability and mineral accessibility.

Main Results:

• Coexposure significantly reduced fresh biomass and compromised nutritional quality.
• Accumulation of reactive oxygen species (ROS) led to compromised chloroplast integrity, stomatal closure, and reduced net photosynthesis.
• Metabolomic analysis revealed reprogramming of plant metabolism, including altered sulfate, benzylamine, and traumatic acid pathways, activating an abscisic acid-ROS signaling loop for lead detoxification.
• Leaf lead bioavailability increased by 16.0%, and mineral bioaccessibility decreased by 7.6-13.2%.

Conclusions:

• Combined heatwaves and PM2.5-Pb exposure trigger physiological and metabolic shifts that drive agricultural losses.
• The findings highlight the compounded threat of atmospheric pollution and climate change to crop yield and food safety.
• Understanding these mechanisms is crucial for developing mitigation strategies in agriculture.