Antioxidant Capacity of Chitosan on Sorghum Plants under Salinity Stress

Takalani Mulaudzi (), Mulisa Nkuna, Gershwin Sias, Ibrahima Zan Doumbia, Njagi Njomo and Emmanuel Iwuoha
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Takalani Mulaudzi: Life Sciences Building, Department of Biotechnology, University of the Western Cape, Private Bag X17, Bellville 7535, South Africa
Mulisa Nkuna: Life Sciences Building, Department of Biotechnology, University of the Western Cape, Private Bag X17, Bellville 7535, South Africa
Gershwin Sias: Life Sciences Building, Department of Biotechnology, University of the Western Cape, Private Bag X17, Bellville 7535, South Africa
Ibrahima Zan Doumbia: Life Sciences Building, Department of Biotechnology, University of the Western Cape, Private Bag X17, Bellville 7535, South Africa
Njagi Njomo: SensorLab, Department of Chemical Sciences, University of the Western Cape, Private Bag X17, Bellville 7535, South Africa
Emmanuel Iwuoha: SensorLab, Department of Chemical Sciences, University of the Western Cape, Private Bag X17, Bellville 7535, South Africa

Agriculture, 2022, vol. 12, issue 10, 1-20

Abstract: Salinity stress is one of the major environmental constraints responsible for the reductions in agricultural productivity. Salinity affects crop growth, by causing osmotic and ionic stresses, which induce oxidative damage due to increased reactive oxygen species (ROS). Exogenous application of natural compounds can reduce the negative impacts of salinity stress on plants. This study evaluated the antioxidant capacity of chitosan, a biopolymer to reduce the salt-induced oxidative damage on sorghum plants. Morpho-physiological and biochemical attributes of sorghum plants stressed with 300 mM NaCl, in combination with chitosan (0.25 and 0.5 mg/mL), were assayed. Salt stress decreased growth, fresh (66.92%) and dry (48.26%) weights, affected the shape and size of the stomata, caused deformation of the xylem and phloem layers, and increased the Na + /K + (1.3) and Na + /Si + (5.4) ratios. However, chitosan effectively reversed these negative effects, as supported by decreased Na + /Si + ratio (~0.9) and formed silica phytoliths. Oxidative stress was exerted as observed by increased H 2 O 2 (44%) and malondialdehyde (125%) contents under salt stress, followed by their reduction in chitosan-treated sorghum plants. Salt increased proline (318.67%), total soluble sugars (44.69%), and activities of SOD (36.04%) and APX (131.58%), indicating sorghum’s ROS scavenging capacity. The antioxidant capacity of chitosan was measured by determining its ability to reduce oxidative damage and minimizing the induction of the antioxidant defense system. Chitosan reduced oxidative stress markers, proline, total soluble sugars, and the antioxidant enzyme activities by more than 50%. Fourier Transform Infrared Spectra of chitosan-treated samples confirmed a reduction in the degradation of biomolecules, and this correlated with reduced oxidative stress. The results suggest that chitosan’s antioxidant capacity to alleviate the effects of salt stress is related to its role in improving silicon accumulation in sorghum plants.

Keywords: anatomical structure; antioxidant; chitosan; FTIR; oxidative stress; ROS; silicon; Sorghum bicolor (search for similar items in EconPapers)
JEL-codes: Q1 Q10 Q11 Q12 Q13 Q14 Q15 Q16 Q17 Q18 (search for similar items in EconPapers)
Date: 2022
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