Application of an in vitro plant ecotoxicity test to unused biodegradable mulches

Biodegradable plastics have emerged as an encouraging alternative to reduce the production of plastic waste, especially for agricultural mulches. However, degradation of these plastics in the field may involve the release of products from the mulch into the soil, before and during the in-soil biodegradation. The present work aims to assess the potential effects on two agricultural plant species (Lactuca sativa L. –lettuce-, and Lycopersicon esculentum Mill. -tomato) of extracts from biodegradable (BDMs: Mater-Bi, Bioplast-SP4 and SP-6, BioFilm, BioFlex, Ecovio, Mirel, Paper) and Polyethylene mulch films. A previously designed highly sensitive in vitro ecotoxicity test was used. Some of the extracts from the biodegradable plastics had effects on plant development. Germination was reduced by Bioplast films treatments, both in lettuce (B-SP4) and in tomato (B-SP4 and B-SP-6). In lettuce, root development was notably reduced by all treatments except for Paper and Polyethylene. Plant aerial growth was also limited with Bioplast and BioFlex, but enhanced with Paper extracts. At a whole, tomato plants showed higher sensitivity than lettuce in the test. Tomato aerial plant part and root growth were reduced by all treatments with the exception of BioFlex and Polyethylene. For both plant species, inhibitory effects on development were associated to proline increases, a physiological marker for some plant stresses. It can be concluded that the contact of unused biodegradable films with a water solution may result in changes in plant development that depend on the nature of the biodegradable film. The in vitro used test revealed to be a highly sensitive tool for ecotoxicity studies. These results are to contribute to design safe materials for agricultural applications.