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.
Highlights
Abiotic stresses can strongly affect plant growth and development and impact crop quality and productivity, primarily if they occur during the most sensitive phenological phases (Bulgari et al, 2019)
In plants treated with NaCl alone, a mortality of 6.6% was observed starting from 14 DAT, while in the biostimulated samples, no mortality was observed
Salt stress caused a decline in plant dry weight (DW) due to a reduction in leaf DW, while it did not affect the DW of roots and stem + lateral shoots (Table 1)
Summary
Abiotic stresses can strongly affect plant growth and development and impact crop quality and productivity, primarily if they occur during the most sensitive phenological phases (Bulgari et al, 2019). Salinity can induce a variety of physiological, morphological, and biochemical changes in plants, affecting plant establishment and causing stunted growth (Lucini et al, 2015). These alterations are due to osmotic and ionic effects, which hamper adequate nutrient acquisition and translocation, reduce enzyme activities and interfere with pivotal metabolic processes such as photosynthesis (Pn; Colantoni et al, 2017). Decreases in stomatal conductance, imposed by saline stress, reduce the CO2:O2 ratio and increase photorespiration to prevent photooxidative damage (Kangasjärvi et al, 2012)
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