Nitric oxide alleviates cadmium-impeded growth by limiting ROS accumulation in pea seedlings

Abstract

Cadmium (Cd) causes oxidative stress, which leads to the oxidation of various biomolecules by the production of reactive oxygen species (ROS) to facilitate programmed cell death (PCD). The antioxidant defense system fails to detoxify ROS when it is produced in excess. Nitric oxide (NO), a gaseous free radical and a phytohormone, regulates various physiological processes of plants. Therefore, this work was undertaken to study the effects of the application of exogenous sodium nitroprusside (SNP, a NO donor) on growth parameters, oxidative stress, accumulation of secondary metabolites, and activities of antioxidant enzymes under Cd stress. Mild (50 µM) and severe (200 µM) Cd stress were applied to hydroponically grown pea (Pisum sativum L.) plants with or without 50 µM SNP. Severe Cd stress had a substantial impact on the plants. The effectiveness of NO in reducing Cd-induced negative effects on plant height, fresh weight, dry weight, protein content, nitrite content, nitrate reductase (NR) activity, catalase activity, and peroxidase activity were investigated. Seedling development, protein content, nitrite content, nitrate reductase (NR) activity, antioxidant defense systems disruption, overproduction of reactive oxygen species, and oxidative damage were observed. The antioxidant defense system (catalase and peroxidase activities) was activated by NO, which resulted in lower lipid peroxidation and lower hydrogen peroxide (H 2 O 2 ) levels in Cd-exposed plants. SNP treatment boosted endogenous NO levels and NR activity in Cd-stressed plants while also enhanced proline levels to preserve osmotic equilibrium. The presence of total phenols and flavonoids increased after SNP treatment, indicating that SNP enhanced stress recovery and boosted plant development in Cd-stressed plants.

Application of Rhizobacteria, Paraburkholderia fungorum and Delftia sp. Confer Cadmium Tolerance in Rapeseed (Brassica campestris) through Modulating Antioxidant Defense and Glyoxalase Systems

“…Moreover, it interrupts the electron transport chain, antioxidant defense, and nutrient metabolism, which ultimately augment the generation of ROS, such as hydrogen peroxide (H 2 O 2), singlet oxygen ( 1 O 2 ), superoxide anion (O 2 •− ), hydroxyl radical ( • OH), etc. Overaccumulated ROS initiates the oxidation of the ultrastructure of biomolecules, e.g., carbohydrates, lipids, proteins, nucleic acids, etc., leading to the oxidative stress of the plants [ 5 , 6 ]. To combat the Cd-induced oxidative stress, plants evolved some avoidance techniques, viz., metal binding, metal chelation, vacuolar sequestration, compartmentalization, etc., to mitigate the pernicious effect of ROS [ 7 , 8 ].…”