Abstract
A significant increase in atmospheric CO2 concentration and associated climate aridization and soil salinity are factors affecting the growth, development, productivity, and stress responses of plants. In this study, the effect of ambient (400 ppm) and elevated (800 ppm) CO2 concentrations were evaluated on the C4 xero-halophyte Kochia prostrata treated with moderate salinity (200 mM NaCl) and polyethylene glycol (PEG)-induced osmotic stress. Our results indicated that plants grown at elevated CO2 concentration had different responses to osmotic stress and salinity. The synergistic effect of elevated CO2 and osmotic stress increased proline accumulation, but elevated CO2 did not mitigate the negative effects of osmotic stress on dark respiration intensity and photosystem II (PSII) efficiency. This indicates a stressful state, which is accompanied by a decrease in the efficiency of light reactions of photosynthesis and significant dissipative respiratory losses, thereby resulting in growth inhibition. Plants grown at elevated CO2 concentration and salinity showed high Na+ and proline contents, high water-use efficiency and time required to reach the maximum P700 oxidation level (PSI), and low dark respiration. Maintaining stable water balance, the efficient functioning of cyclic transport of PSI, and the reduction of dissipation costs contributed to an increase in dry shoot biomass (2-fold, compared with salinity at 400 ppm CO2). The obtained experimental data and PCA showed that elevated CO2 concentration improved the physiological parameters of K. prostrata under salinity.
Highlights
According to the Intergovernmental Panel on Climate Change (IPCC), a significant increase in atmospheric CO2 concentration, associated climate aridization, and soil salinity are factors affecting the growth, development, and functioning of plants, which can potentially change the composition of plant communities, spread of ecosystems, and lead to a catastrophic decrease in biodiversity [1,2,3]
The C4 xero-halophyte Kochia prostrata grown at an ambient CO2 concentration was intolerant to moderate osmotic stress and salinity
A study on CO2/H2O gas exchange in K. prostrata showed that the intensity of apparent photosynthesis (A) did not significantly change at elevated CO2 as well as at PEGinduced osmotic stress and moderate salinity with a similar osmotic potential (Figure 2a)
Summary
According to the Intergovernmental Panel on Climate Change (IPCC), a significant increase in atmospheric CO2 concentration, associated climate aridization, and soil salinity are factors affecting the growth, development, and functioning of plants, which can potentially change the composition of plant communities, spread of ecosystems, and lead to a catastrophic decrease in biodiversity [1,2,3]. Issues related to the impact of global climatic changes on vegetation are leading in biological science. C4 plants have long been considered less dependent on environmental CO2 concentration than their C3 counterparts due to the presence of a carbon-concentrating mechanism (CCM), which makes them less responsive to an increase in atmospheric CO2 concentration [4,5]. This concept is deeply embedded in climatic and ecological models of climate change impact on plants [5,6,7]. It was shown that in C4 halophytes of the Chenopodiaceae family, a high CO2 concentration more effectively stimulates photosynthetic metabolism than in C3 species [8]
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