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Photosynthetic Adaptations and Oxidative Stress Tolerance in Halophytes from Warm Subtropical Region

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Handbook of Halophytes

Abstract

This chapter attempts to synthesize recent work related to photosynthetic adaptations and oxidative stress mitigation mechanisms of perennial warm subtropical halophytes of Karachi, Pakistan. In most species the light-harvesting photochemical reactions appear less sensitive to increase in salinity treatments in comparison with those of carbon fixation. This was evident from unaltered Fv/Fm values which indicate the maximum photochemical efficiency and the degree of photoinhibition of PSII. However, there was a reduction in electron transport rate (ETR) and a rise in non-photochemical quenching (NPQ) by heat dissipation. Decrease in net photosynthetic rates (PN), stomatal conductance (gs), and transpiration rates (E) with concomitant increases in salinity indicate downregulation of key photosynthetic processes as a survival strategy under harsh conditions by improving or maintaining water use efficiency (WUE) in most species. At the biochemical level increases in salinity resulted in an increase in H2O2 content. Consequently, increased or constitutively high superoxide dismutase (SOD) and catalase (CAT) activities with high ascorbate and glutathione contents were observed in response to salinity treatments as key protective antioxidant responses to prevent oxidative damage under low to moderate salinity. At higher salinity treatments, rise in malondialdehyde (MDA) content could indicate insufficiency of antioxidant system against excessive ROS. An attempt has been made to find ecological arguments for differences in the abovementioned physiological and biochemical responses of halophytes; however further studies are needed.

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Correspondence to Abdul Hameed .

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Gulzar, S., Hussain, T., Gul, B., Hameed, A. (2020). Photosynthetic Adaptations and Oxidative Stress Tolerance in Halophytes from Warm Subtropical Region. In: Grigore, MN. (eds) Handbook of Halophytes. Springer, Cham. https://doi.org/10.1007/978-3-030-17854-3_52-1

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  • DOI: https://doi.org/10.1007/978-3-030-17854-3_52-1

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  • Publisher Name: Springer, Cham

  • Print ISBN: 978-3-030-17854-3

  • Online ISBN: 978-3-030-17854-3

  • eBook Packages: Springer Reference Biomedicine and Life SciencesReference Module Biomedical and Life Sciences

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