Effects of Megafol on the Olive Cultivar ‘Arbequina’ Grown Under Severe Saline Stress in Terms of Physiological Traits, Oxidative Stress, Antioxidant Defenses, and Cytosolic Ca2+

Abstract

Salinity is one of the most impacting abiotic stresses regarding crop productivity and quality. Among the strategies that are attracting attention in the protection of crops from abiotic stresses, there is the use of plant biostimulants. In this study, Megafol (Meg), a commercial plant biostimulant, was tested on olive plants subjected to severe saline stress. Plants treated with salt alone showed substantial reductions in biomass production, leaf net photosynthesis (Pn), leaf transpiration rate (E), stomatal conductance (gs), and relative water content (RWC). In addition, samples stressed with NaCl showed a higher sodium (Na+) content in the leaves, while those stressed with NaCl and biostimulated with Meg increased the potassium (K+) content in the leaves, thus showing a higher K+/Na+ ratio. Salinity caused the accumulation of significant quantities of hydrogen peroxide (H2O2) and malondialdehyde (MDA) due to decreases in the activity of antioxidant enzymes, namely superoxide dismutase (SOD – EC 1.15.1.1), ascorbate peroxidase (APX – EC 1.11.1.11), guaiacol peroxidase (GPX – EC 1.11.1.9), and catalase (CAT – EC 1.11.1.6). When olive plants under saline stress were biostimulated with Meg, the plants recovered and showed physiological and biochemical traits much improved than salt stressed samples. Finally, Meg exhibited Ca2+-chelating activity in olive pollen grains, which allowed the biostimulant to exert this beneficial effect also by antagonizing the undesirable effects of hydrogen peroxide on Ca2+ metabolism.

Use of a Biostimulant to Mitigate Salt Stress in Maize Plants

“…Salinity is among the abiotic stresses that have the highest detrimental effects on agriculture for its ability to interfere with crop development and quality [1]. Furthermore, salt stress mainly affects crop production in regions with an arid or semi-arid climate, particularly the coastal areas [6]. Therefore, implementing practices and innovations that can contain the deleterious effects of such stress is considered essential to maintaining acceptable crop yields.…”

“…Several hypotheses have been formulated to explain the mechanisms of tolerance/resistance of crops to salinity, but, in many cases, they are dependent on the species in question. In general, however, among the most critical pathways adopted by species to counteract the deleterious effects of salinity mechanisms, the controlling of Na + uptake and ROS production are reputed of particular importance [2,6,46,47]. Regarding the latter aspect, a large body of literature documents that salinity causes oxidative stress, and this mainly affects chloroplasts and mitochondria with negative consequences on their functionality [6,46,47].…”

“…Salinity impacts crops by negatively affecting plant establishment and causing stunted growth [6]. High salt concentrations exert direct toxicity on plants or lead to nutritional disorders [7].…”

Physiological and Biochemical Mechanisms of Exogenously Applied Selenium for Alleviating Destructive Impacts Induced by Salinity Stress in Bread Wheat

“…Furthermore, salinity constrains plant growth by producing a high level of reactive oxygen species (ROS), such as hydrogen peroxide (H 2 O 2 ), superoxide (O 2 − ) and hydroxyl radicals (OH − ) [7]. ROS is defined as the residue of normal cellular metabolism and is significant for the reaction of enzymatic intracellular coding when plants present salinity stress [8,9]. The grown plants under salinity suffer from toxic effects of Na + and Cl − ions and nutrient imbalance and diminish water availability in the soil [10].…”

Jute Responses and Tolerance to Abiotic Stress: Mechanisms and Approaches

“…Other stresses like toxic metals/metalloids, heat, and high light also have a negative effect on jute growth and physiology [ 2 , 11 ]. Under stressful conditions, the excess generation of reactive oxygen species (ROS)-induced oxidative damage in jute can be scavenged by a large number of ROS detoxifying antioxidant enzymes [ 12 , 13 ].…”