Studying the effects of salicylic acid and silicon on growth, yield and some physiological parameters of spring rapeseed under water limitation

Sajed Gollojeh, Kamel (2020) Studying the effects of salicylic acid and silicon on growth, yield and some physiological parameters of spring rapeseed under water limitation. Doctoral thesis, University of Mohaghegh Ardabili.

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Abstract

Research Aim: The use of nutrient nanoparticles and exogenous plant growth regulators by influencing plant physiological processes can play an important role in tolerance to water limitation. The aim of this study was to investigate the changes of growth, some physiological traits and seed yield of spring rapeseed in response to foliar spray of Nano-silicon dioxide (nSiO2) and salicylic acid (SA) under water limitation conditions. Research method: This experiment was conducted as a factorial split plot based on a randomized complete block design with four replications at the Faculty of Agriculture and Natural Resources, University of Mohaghegh Ardebili, in 2017 and 2018 years. Water limitation treatments (control or full irrigation, irrigation withholding at stem elongation, flowering and seed formation stages), and foliar spray of silicon in form of Nano- silicon dioxide (nSiO2) at three levels (0, 60 and 300 mg.L-1) and salicylic acid (SA) at three levels (0, 0.5 and 2.5 mM). Findings: The results of combined analysis showed that the effect of year was significant on some of growth, physiology and seed yield components traits. Water limitation was caused to decrease of growth, yield and seed yield treats, so the foliar application resulting improvements of growth traits, yield and yield components of rapeseed plants. The results showed significant differences in both main and interaction effects of experimental factors on agro-physiological and biochemical characteristics as well as seed yield. Water limitation was caused to significantly decrease of plant height in both experiments years, whereas foliar application of nSiO2 and SA led to improve of this trait. In full irrigation, the highest value of relative water content (RWC) was obtained, especially with foliar spray 300 mg.L-1 nSiO2. The foliar spray 2.5 mM SA also caused the highest RWC than others treatments. Foliar Spray 300 mg.L-1 of nSiO2 with SA consumption resulted in the reduction of cell membrane injury (MI). In all irrigation treatments, 60 mg.L-1 nSiO2 with 0.5 and 2.5 mM SA and/or SA alone had the better resulted in photosynthetic pigments concentration. The proline content was considerably elevated in response withholding irrigation, also the maximum increase of catalase activity was observed at I3 condition when 300 mg.L-1 nSiO2 and 2.5 mM SA were applied. The maximum increase in guaiacol peroxidase activity was observed at I4 condition with application of 300 mg L-1 nSiO2 only with distilled water. The highest seed yield was obtained from applied of 300 mg.L-1 with 0.5 nSiO2 and or 2.5 mM of SA at normal irrigation (control treatment) and the lowest was belonged to non-foliar application especially under severity water limitation. Conclusion: Increasing in quantum efficiency of photosystem II (Fv/Fm), RWC and decreasing in MI was the positive effects of foliar application of nSiO2 alone and/or combined with SA especially at severity water limitation stress. Also applied of nSiO2 with low concentration of SA was caused to increasing antioxidant enzyme activity under severity water limitation. In term of seed yield, foliar spray was led to improve 38% in compared control at first experiment year. In second year, the highest seed yield was obtained at normal irrigation with high level of foliar application. The findings of this experiment demonstrated that exogenous application of Nano-silicon dioxide and salicylic acid can be alleviated the deleterious impacts of end-season water limitation. It was concluded that foliar spray nSiO2 and SA alone or combined in both conditions of irrigation and or water limitation showed a positive effect on physiological traits and seed yield, however a higher amount of nSiO2 could have a deterrent effect on the positive effects of SA. In conclusion, the foliar application of rather low concentrations of nSiO2 and SA around anthesis can ameliorate harmful effects of end-season water limitation and consequently improve final yield of spring canola.

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