Attenuation of negative effects of saline stress in wheat plant by chitosan and calcium carbonate

Abstract

Abstract Background Chitosan and Ca+ are natural signal molecules that can be used in agriculture as biostimulants and elicitors. They enhance different physiological responses and mitigate the negative effects of salinity. So, this investigation was done to study the effect of soaking wheat grains in chitosan and CaCO3 (20 and 40 mg/L) on alleviating the adverse effect of salinity stress (0.0 and 5000 mg/L) on growth, some biochemical and physiological and yields of wheat plant. Results Shoot length (cm), leaves no/tiller, shoot dry weight (g), root fresh weight (g) and root dry weight (g) were significantly decreased as a result of salt stress. Soaking wheat grains in Chitosan or CaCO3 significantly promoted plant growth under normal and stressed conditions. Irrigation of wheat plants with saline water significantly decreased photosynthetic pigments (Chlo-a, Chlo-b, carotenoids and total pigments) in addition to Chlo-a/Chlo-b ratio, indole acetic acid content in the plant leaves. Meanwhile, saline water significantly increased phenolics, total soluble sugars (TSS) and proline content. H2O2 and lipid peroxidation expressed by malondialdehyde (MDA) content clearly showed significant increases under salinity stress compared with untreated control. Soaking wheat grains in chitosan or CaCO3 before sawing significantly increased the accumulation of H2O2 and MDA in the leaves of wheat plants. Treatment of wheat grains with chitosan or CaCO3 significantly promoted the activity of various antioxidant enzymes (SOD and POX) as compared to the control. CAT activity was significantly decreased as a result of chitosan or CaCO3 treatments. The highest CAT activity was recorded in plants irrigated with 5000 mg/L saline water followed by control plants which recoded 36.40 and 24.82 U/min/g FW, respectively. On the other hand, irrigation of wheat plants with 5000 mg/L saline water significantly decreased spike length (cm), spikelets no/spike, grains wt/plant (g), 1000-grains wt (g), yield and biomass/plant (g) as well as, carbohydrate % and protein % compared with the control. However, treating wheat plants either with Chitosan or calcium carbonate resulted in obvious significant increases in carbohydrates and protein contents, especially in plants treated with 40 mg/L chitosan followed by 40 mg/L calcium carbonate. Soaking wheat grains in chitosan, especially at 40 mg/L, exhibited the strongest scavenging potential (2,2-diphenyl-1-picryl-hydrazyl-hydrate assay (DPPH%) followed by treatment with 40 mg/L CaCO3. Conclusion In conclusion, the used treatment enhanced the protective parameters such as antioxidant enzymes, total phenols and free radical scavengers and consequently helped the plants to decrease lipid peroxidation, increased their tolerance and improved yield and spike quality. Application of 40 mg/L chitosan recorded the highest increment in the scavenging ability of the natural antioxidants of the plant extract toward the stable free radical DPPH.