RESUMO
One of the main environmental stresses that hinder crop development as well as yield is salt stress, while the use of signal molecules such as calcium (Ca) has a substantial impact on reducing the detrimental effects of salt on different crop types. Therefore, a factorial pot experiment in a completely randomized design was conducted to examine the beneficial role of Ca (0, 2.5, and 5 mM) in promoting the physiological, biochemical, and growth traits of the wheat plant under three salt conditions viz. 0, 30, and 60 mM NaCl. Foliar application of Ca increased the growth of salt-stressed wheat plants through increasing photosynthetic pigments, IAA, proline, and total soluble sugars contents and improving antioxidant enzymes in addition to non-enzymatic antioxidants glutathione, phenol and flavonoids, ß-carotene, and lycopene contents, thus causing decreases in the over-accumulation of free radicals (ROS). The application of Ca increased the activity of antioxidant enzymes in wheat plants such as superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), which scavenge reactive oxygen species (ROS) and relieved salt stress. An additional salt tolerance mechanism by Ca increases the non-antioxidant activity of plants by accumulating osmolytes such as free amino acids, proline, and total soluble sugar, which maintain the osmotic adjustment of plants under salinity stress. Exogenous Ca application is a successful method for increasing wheat plants' ability to withstand salt stress, and it has a considerable impact on the growth of wheat under salt stress.
RESUMO
Salinity is the primary environmental stress that adversely affects plants' growth and productivity in many areas of the world. Published research validated the role of aspartic acid in improving plant tolerance against salinity stress. Therefore, in the present work, factorial pot trials in a completely randomized design were conducted to examine the potential role of exogenous application of aspartic acid (Asp) in increasing the tolerance of wheat (Triticum aestivum L.) plants against salt stress. Wheat plants were sown with different levels of salinity (0, 30, or 60 mM NaCl) and treated with three levels of exogenous application of foliar spray of aspartic acid (Asp) (0, 0.4, 0.6, or 0.8 mM). Results of the study indicated that salinity stress decreased growth attributes like shoot length, leaf area, and shoot biomass along with photosynthesis pigments and endogenous indole acetic acid. NaCl stress reduced the total content of carbohydrates, flavonoid, beta carotene, lycopene, and free radical scavenging activity (DPPH%). However, Asp application enhanced photosynthetic pigments and endogenous indole acetic acid, consequently improving plant leaf area, leading to higher biomass dry weight either under salt-stressed or non-stressed plants. Exogenous application of Asp, up-regulate the antioxidant system viz. antioxidant enzymes (superoxide dismutase, peroxidase, catalase, and nitrate reductase), and non-enzymatic antioxidants (ascorbate, glutathione, total phenolic content, total flavonoid content, beta carotene, lycopene) contents resulted in declined in reactive oxygen species (ROS). The decreased ROS in Asp-treated plants resulted in reduced hydrogen peroxide, lipid peroxidation (MDA), and aldehyde under salt or non-salt stress conditions. Furthermore, Asp foliar application increased compatible solute accumulation (amino acids, proline, total soluble sugar, and total carbohydrates) and increased radical scavenging activity of DPPH and enzymatic ABTS. Results revealed that the quadratic regression model explained 100% of the shoot dry weight (SDW) yield variation. With an increase in Asp application level by 1.0 mM, the SDW was projected to upsurge through 956 mg/plant. In the quadratic curve model, if Asp is applied at a level of 0.95 mM, the SDW is probably 2.13 g plant-1. This study concluded that the exogenous application of aspartic acid mitigated the adverse effect of salt stress damage on wheat plants and provided economic benefits.
RESUMO
The interactive effects of saline water (2000, 4000 and 6000 mg/l) and foliar application of 400 mg/l of ascorbic acid (Asc) or α- tocopherol (α-Toco) on three flax cultivars (Sakha 3, Giza 8 and Ariane) were conducted during two successive seasons 2011/2012 and 2012/2013. The results showed that total soluble carbohydrates, free amino acids and proline contents were significantly increased with increasing salinity levels in the all three tested cultivars except free amino acid content of Giza 8 which showed insignificant decrease. While, nucleic acids (DNA and RNA) showed significant decreases compared with the corresponding control. Moreover, applications of vitamins (Asc or α-Toco) as foliar spraying increased all mentioned contents compared to the corresponding salinity levels. On the other hand, lipid peroxidation and activity levels of polyphenol oxidase, peroxidase and catalase enzymes showed significant increases with increasing salinity levels of all tested three cultivars, while the behaviour of superoxide dismutase activity showed an opposite response as compared with the control in Sakha 3 and Giza 8. Treatments with Asc or α-Toco induced significant reduction in lipid peroxidation and activities of polyphenol oxidase, peroxidase of the all three tested cultivars. Meanwhile, superoxide dismutase increased in all three cultivars, and catalase activities increased only in Sakha 3 cultivar under salt stress as compared with reference controls. Some modifications are observed in protein patterns hence some proteins were disappeared, while certain other proteins were selectively increased and synthesised of a new set of proteins were induced, some of these responses were observed under treatments and salinity, while others were induced by either treatments or salinity.
La interacción de los efectos del agua salada (2000, 4000 and 6000 mg/l) y la aplicación foliar de 400 mg/l de ácido ascórbico (Asc) o α-tocopherol (α-Toco) en tres cultivares de lino (Sakha 3, Giza 8 y Ariane) se analizó durante dos estaciones sucesivas (2011- 2012). Los resultados mostraron que los contenidos de carbohidratos solubles totales, aminoácidos libres y prolina aumentaron significativamente con los niveles crecientes de salinidad en los tres cultivares probados, excepto en el cultivar Giza 8, en el cual el contenido de aminoácidos libres se redujo. Al mismo tiempo, los ácidos nucleicos (ADN y ARN) mostraron disminuciones significativas en comparación con los controles correspondientes. Mientras que aplicaciones foliares de vitaminas (Asc o α-Toco) incrementaron los contenidos mencionados en comparación con los niveles de salinidad. De otro lado, la peroxidación de lípidos y la actividad de la polifenol oxidasa, la peroxidasa, y la catalasa mostraron incrementos significativos con los niveles crecientes de salinidad en los tres cultivares analizados. Mientras tanto, la actividad superóxido dismutasa se incrementó en los tres cultivares y la actividad catalasa se incrementó únicamente en el cultivar Sakha 3 bajo estrés salino, en comparación con los controles. Se observaron algunas modificaciones en los patrones de proteínas. Así, algunas proteínas desaparecieron mientras que otras incrementaron e incluso un nuevo set de proteínas fue inducido. Algunas de estas respuestas fueron observadas en los tratamientos y en la salinidad, mientras que otras fueron inducidas por los tratamientos o por la salinidad.
