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Rice is one of the most important crops in the world and is considered a strategic crop for food security. Furthermore, the excessive use of chemical fertilizers to obtain high yields causes environmental problems. A sustainable alternative includes taking advantage of beneficial bacteria that promote plant growth. Here, we investigate the effect of five bacterial biofertilizers from halophytes on growth, and we investigate photosynthetic efficiency in rice plants grown under saline conditions (0 and 85 mmol L−1 NaCl) and future climate change scenarios, including increased CO2 concentrations and temperature (400/700 ppm and 25/+4 °C, respectively). Biofertilizers 1–4 increased growth by 9–64% in plants grown with and without salt in both CO2- temperature combinations, although there was no significant positive effect on the net photosynthetic rate of rice plants. In general, biofertilizer 1 was the most effective at 400 ppm CO2 and at 700 ppm CO2 +4 °C in the absence of salt. Inocula 1–5 also stimulated plant length at high CO2 levels without salt. Finally, the positive effect of biofertilization was attenuated in the plants grown under the interaction between salt and high CO2. This highlights the significance of studying biofertilization under stress interaction to establish the real potential of biofertilizers in the context of climate change conditions. [ABSTRACT FROM AUTHOR]

Biofertilization with plant-growth-promoting rhizobacteria (PGPR) can positively affect the growth and health of host plants and reinforce their tolerance of stressors. Here, we investigate the use of isolated PGPR consortia from halophytes to improve strawberry growth and flowering performance under saline and elevated CO2 and temperature conditions. Growth, flower bud production, and the photosynthetic apparatus response were determined in strawberry plants grown at 0 and 85 mmol L−1 NaCl and in two atmospheric CO2-temperature combinations (400/700 ppm and 25/+4 °C, respectively). Biofertilization improved strawberry plant growth and flower bud production, independently of salinity conditions, at ambient CO2 and 25 °C, while bacterial inoculation only had a positive effect on plant growth in the presence of salt in high CO2 and at +4 °C. Biofertilizers 1 and 3 generated the largest biomass of strawberries at 400 ppm CO2 and 0 and 85 mmol L−1 NaCl, respectively, while biofertilizer 1 did so in the presence of salt and in an atmosphere enriched with CO2 and at +4 °C. The effect of the consortia was mediated by bacterial strain PGP properties, rather than by an improvement in the photosynthetic rate of the plants. Furthermore, biofertilizers 1 and 2 increased the number of flower buds in the absence of salt, while biofertilizers 3 and 4 did so for salt-inoculated plants at 400 ppm CO2 and at 25 °C. There was no effect of inoculation on flower bud production of plants grown at high CO2 and at +4 °C. Finally, we concluded that the effect of bacterial inoculation on strawberry growth and flowering depended on the type of bacterial strain and growth conditions. This highlights the importance of developing studies considering stress interaction to assess the real potential of biofertilizers. [ABSTRACT FROM AUTHOR]

The potential importance of Juncus acutus for remediation of Zn-contaminated lands has been recognized, because of its Zn tolerance and capacity to accumulate Zn. Since it is also a halophyte, the extent to which salinity influences its Zn tolerance requires investigation. A factorial greenhouse experiment was designed to assess the effect of NaCl supply (0 and 85 mM NaCl) on the growth, photosynthetic physiology and tissue ions concentrations of plants exposed to 0, 30 and 100 mM Zn. Our results indicated that NaCl supplementation alleviated the effects of Zn toxicity on growth, as Zn at 100 mM reduced relative growth rate (RGR) by 60% in the absence of NaCl but by only 34% in plants treated also with NaCl. This effect was linked to a reduction in Zn tissue concentrations, as well as to overall protective effects on various stages in the photosynthetic pathway. Thus, at 85 mM NaCl plants were able to maintain higher net photosynthesis (A N ) than in the absence of added NaCl, although there were no differences in stomatal conductance (g s ). This contributed to preserving the trade-off between CO 2 acquisition and water loss, as indicated by higher intrinsic water use efficiency ( i WUE). Hence, A N differences were ascribed to limitation in the RuBisCO carboxylation, manifested as higher intercellular CO 2 concentration (C i ), together with dysfunction of PSII photochemistry (in term of light harvest and energy excess dissipation), as indicated by higher chronic photoinhibition percentages and variations in the photosynthetic pigment profiles in presence of Zn under non-saline conditions. [ABSTRACT FROM AUTHOR]

Inadequate fertilization or the indiscriminate use of water with high salt concentrations have led to salinization of agricultural soils. In this context, biofertilization with plant-growth-promoting rhizobacteria (PGPR) is an environmentally benign strategy to stimulate plant growth, even under salt stress. Thus, we studied the use of isolated PGPR consortia from halophytes to enhance Swiss chard growth under saline conditions. Growth, photosynthetic apparatus response, nutrient status, pigment concentrations, and secondary metabolites with antioxidant activity were determined in Swiss chard plants grown at 0 and 85 mmol L−1 NaCl. In general, inoculation of plants with PGPR has been shown to be an effective strategy to stimulate the growth of Swiss chard and improve its tolerance to salt stress. Inoculated plants watered with 85 mmol L−1 NaCl showed higher values of leaf dry weight than control plants. Furthermore, PGPR inoculation reduced electrolyte leakage and Na+ uptake and improved chlorophyll a fluorescence parameters, chlorophyll and carotenoid concentrations, stomatal conductance, and antioxidant capacity of Swiss chard. Finally, our findings highlight the potential of isolated PGPR from halophytes to counterbalance the deleterious effect of salinity and stimulate crop growth. [ABSTRACT FROM AUTHOR]

• Impact of a complex environmental matrix on S. maritima performance was evaluated. • Temperature and atmospheric CO 2 increments had synergic injury effects. • These conditions drastically reduced plant growth and increased its senescence. • Carbon assimilation, light-harvesting and photoprotective impacts were found. • Atmospheric CO 2 enrichment would limit stomata ability to cope with heat excess. A challenge exists in the need to understand plant responses in complex environmental matrixes, such as those predicted by climate change models, being this information essential for species that support important ecosystem functions. A factorial climatic chamber experiment was designed to evaluate the impact of atmospheric CO 2 concentration (400 ppm and 700 ppm CO 2) in combination with two maximum and minimum temperature ranges (28/13 °C and 32/17 °C) and salinity concentrations (0 and 171 mM NaCl) on the growth and photosynthetic responses of the ecosystem engineer species Spartina maritima. Plants grown at 32/17 °C showed a reduction ∼39 % on relative growth rate (RGR) and this was more drastic (i.e. 64 %) in those exposed to 700 ppm CO 2 , which also showed an increment in the percentage of dead tillers regardless of salinity. These reductions were explained by the negative impact on net photosynthetic rate (A N), which decreased with temperature increment, being this reduction more acute at 700 ppm CO 2. This response was associated with an augmentation in CO 2 diffusion limitations, as indicated the lower stomatal conductance (g s), together with a down-regulation photochemical apparatus efficiency, as indicated the lower electron transport rate (ETR) and energy fluxes derived from Kautsky curves. In addition, the greatest g s drop at 700 ppm CO 2 , would limit plant ability to cope with temperature excess through evapotranspiration, a fact that could have boosted temperature-triggered damage and, consequently, leaf senescence. Therefore, we can conclude that temperature and atmospheric CO 2 increments would compromise the development of S. maritima and consequently the maintaining of its ecosystem functions. [ABSTRACT FROM AUTHOR]

Plant growth promoting bacteria' (PGPB) beneficial role on plant tolerance to salinity stress has previously been well recognized. However, bacteria-triggered plant physiological mechanisms involved in this response require investigation, especially in plants with innate salt tolerance. A glasshouse experiment was designed to investigate the effect of the PGPB Vibrio spartinae on Halimione portulacoides growth, physiological performance and ion homeostasis in plants exposed to 0, 171, 510 and 1020 mM NaCl for 100 days. Bacterial inoculation alleviated ~28% of the deleterious impact of salinity excess on the relative growth rate (RGR) in plants grown at 510 mM and led to 30% and 44% enhancements in those exposed to 0 and 171 mM NaCl, respectively. This effect was linked to a reduction in Na tissue concentrations which improved plant ion homeostasis at elevated NaCl concentration, and to the overall protective effects on various steps in the photosynthetic pathway between 0 and 510 mM NaCl. Thus, inoculated plants were able to maintain higher net photosynthesis (A N) than their non-inoculated counterparts. Hence, A N differences under saline conditions were ascribed to inoculation amelioration NaCl-induced CO 2 diffusion limitations, as reflected in the greater g s and C i values recorded at 171 and 510 mM NaCl, together with an enhancement of photochemical apparatus functionality (in terms of energy absorption, transformation and transport), as indicated by a higher electron transport rate (ETR) and energy fluxes derived from Kautsky curves, compared with their non-inoculated counterparts. • Role of PGPB on NaCl tolerance of the halophytic H. portulacoides was analyzed. • PGPB inoculation alleviates ~28% salinity excess impact on growth at 510 mM NaCl. • PGPB inoculation reduces Na leaf concentration and improves ions homeostasis. • PGPB has a positive effect on various key steps in the photosynthetic pathway. • PGPB reduces NaCl-induced CO 2 transport limitation and enhances PSII functionality. [ABSTRACT FROM AUTHOR]