Incubation Time and Size Effects of Biodegradable Mulch Microplastics on Lettuce Plantlets In Vitro

Area of Science:

• Environmental Science
• Agricultural Science
• Ecotoxicology

Background:

• Biodegradable mulch films (BDM) release microplastics (MPs) into agricultural soils.
• The impact of BDM MPs on plant development, considering particle size and soil residence time, is poorly understood.
• Existing studies on BDM MPs effects yield contrasting results.

Purpose of the Study:

• To investigate the effects of biodegradable mulch film microplastic (BDM MP) size and pre-incubation time on lettuce development.
• To determine how varying MP sizes and incubation periods influence plantlet growth, root architecture, germination, and photosynthetic pigments.
• To elucidate the dynamic interactions between BDM MPs and plants over time.

Main Methods:

• Controlled in vitro lettuce culture.
• Use of BDM MP fractions ranging from 5 to <0.2 mm.
• Pre-incubation of MPs in the growth medium for 0 to 8 weeks prior to seeding.

Main Results:

• Short incubation times (1-2 weeks) and fresh BDM MPs inhibited plantlet growth, with smaller MPs having a stronger negative effect.
• Extended incubation (8 weeks) promoted plantlet development, enhancing leaf and root elongation while reducing lateral root branching.
• MP size influenced root development, with smaller particles causing more pronounced effects.
• Germination and photosynthetic pigments remained unaffected across all treatments.

Conclusions:

• The impact of BDM MPs on plant development is significantly influenced by particle size and incubation time.
• Adverse effects on plant growth observed at short incubation times were mitigated or reversed with longer incubation periods.
• Understanding the temporal dynamics of BDM MP-plant interactions is crucial for assessing agricultural impacts.