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Differences in photosynthetic syndromes of four halophytic marsh grasses in Pakistan

Moinuddin, Muhammad, Gulzar, Salman, Hameed, Abdul, Gul, Bilquees, Ajmal Khan, M., Edwards, Gerald E.
Photosynthesis research 2017 v.131 no.1 pp. 51-64
Aeluropus, C4 photosynthesis, C4 plants, Paspalum distichum, Sporobolus, antioxidants, ascorbate peroxidase, biomass, carbon, carbon dioxide fixation, coasts, ecosystems, environmental factors, grasses, halophytes, isotopes, leaves, lutein, photostability, salinity, salt marshes, salt tolerance, sodium chloride, stomatal conductance, superoxide dismutase, water use efficiency, Pakistan
Salt-tolerant grasses of warm sub-tropical ecosystems differ in their distribution patterns with respect to salinity and moisture regimes. Experiments were conducted on CO₂ fixation and light harvesting processes of four halophytic C₄ grasses grown under different levels of salinity (0, 200 and 400 mM NaCl) under ambient environmental conditions. Two species were from a high saline coastal marsh (Aeluropus lagopoides and Sporobolus tremulus) and two were from a moderate saline sub-coastal draw-down tidal marsh (Paspalum paspalodes and Paspalidium geminatum). Analyses of the carbon isotope ratios of leaf biomass in plants indicated that carbon assimilation was occurring by C₄ photosynthesis in all species during growth under varying levels of salinity. In the coastal species, with increasing salinity, there was a parallel decrease in rates of CO₂ fixation (A), transpiration (E) and stomatal conductance (g ₛ), with no effect on water use efficiency (WUE). These species were adapted for photoprotection by an increase in the Mehler reaction with an increase in activity of PSII/CO₂ fixed accompanied by high levels of antioxidant enzymes, superoxide dismutase and ascorbate peroxidase. The sub-coastal species P. paspalodes and P. geminatum had high levels of carotenoid pigments and non-photochemical quenching by the xanthophyll cycle.