ALTERATIONS INDUCED BY 4 HERBICIDES ON LUPINE NODULE CORTEX STRUCTURE, PROTEIN-METABOLISM AND SOME SENESCENCE-RELATED ENZYMES

In this work we investigated the effects of four herbicides from different chemical groups on nodule cortex structure, nitrogenase activity, protein metabolism, and catalase and peroxidase, enzymes that play a role in the protection of tissues against toxic oxygen species. Alachlor and carbetamide affected the layers of thick-walled cells present in lupine nodule cortex in different ways. These layers are related to the regulation of a variable oxygen diffusion barrier in lupine nodules. Alachlor increased the number of these layers, while carbetamide application caused them to disappear. Protein metabolism was altered in leaves following carbetamide and metribuzin application. The main alteration was the appearance of a polypeptide of 17 kDa, which was absent in control plants. Metribuzin and carbetamide application produced a strong decrease in nitrogenase activity, which can be related to damage in the photosynthetic apparatus (metribuzin) or also to alterations in the nodule cortex structure (carbetamide). In both cases, activities of cytosolic catalase and peroxidase were altered, suggesting nodule senescence.