Vermicompost humic acids as an ecological pathway to protect rice plant against oxidative stress

Humic substances (HS) contained in the vermicompost, are environmentally friendly materials that restore the chemical and physical properties of soils and improve plant growth. The work described herein was aimed at studying the HA-root interactions and their relationship with some components of antioxidative metabolism in rice (Oryza sativa L.). These studies encompassed aspects ranging from the activity of enzymes in antioxidative metabolism and the relationship between these enzymes and the reactive oxygen species (ROS) content in rice to the expression of genes encoding rice tonoplast intrinsic proteins (OsTIP), a sub-family of aquaporins. The HA-root interactions were also characterized. The results from these studies demonstrate that the interaction of HA with the radicular system in plants activates antioxidative enzymatic function, thus controlling the ROS content and modifying OsTIP expression. Microscopic and spectroscopic techniques confirmed the interactions between HA fragments of lower structural complexity and the radicular system. It appears that HA act in plants via a specific form of stress that is detected by anti-stress defense systems in plants. These HA applied to plants can protect against water stress in degraded soils.