Polyethylene microplastic modulates lettuce root exudates and induces oxidative damage under prolonged hydroponic...

Area of Science:

• Environmental Science
• Plant Biology
• Soil Science

Background:

• Root exudates play a crucial role in plant stress responses.
• The impact of microplastics (MPs) on root exudate characteristics is not well understood.
• Polyethylene (PE) MPs are common environmental contaminants.

Purpose of the Study:

• To investigate the effects of polyethylene microplastics (PE MPs) on lettuce (Lactuca sativa L.) growth and physiology.
• To analyze the changes in root exudate composition and characteristics induced by PE MPs.
• To assess the oxidative stress response in lettuce exposed to PE MPs.

Main Methods:

• Lettuce was exposed to 0.05% and 0.1% (w/w) PE MPs for 28 days.
• Root exudates were analyzed using UV-vis spectrophotometry and 3D-Excitation-Emission Matrix (3D-EEM) fluorescence.
• Agronomic traits, pigment content, root activity, and oxidative stress markers (ROS, CAT, POD) were measured.

Main Results:

• PE MPs increased leaf number but had varied effects on root growth (0.05% PE enhanced root length/surface area).
• Higher PE MP concentration (0.1%) reduced dissolved organic carbon (DOC) in root exudates.
• PE MPs increased the aromaticity and hydrophobicity of root exudates, indicated by SUVA values, and induced oxidative stress (ROS) in lettuce leaves.

Conclusions:

• Polyethylene microplastics can alter root exudate composition, increasing aromatic and hydrophobic components.
• While low PE MP concentrations may offer some growth benefits, higher concentrations can negatively impact root exudate quality and induce oxidative stress.
• Prolonged exposure to PE MPs poses potential risks to lettuce growth and health, highlighting the need for further environmental risk assessment.