## 3 Discussion
It has been described as functioning as a structural stabilization of antenna proteins and as a light-harvesting contributor. Due to the long half-life time of its light-activated state, it is feeding excitation energy to Chl [60; 65]. At 400 mM, the higher lutein concentration found in the inoculated plants was paralleled by a significantly higher zeaxanthin concentration. These changes in the lutein and zeaxanthin concentrations allied to a significantly higher RC II density within the antenna chlorophyll bed and increased PSII antenna size, point toward an increased photoprotective ability under PGPR inoculation [39; 59]. Moreover, the content of auroxanthin, a noteworthy carotenoid due to its well-described role as an effective energy quencher under salinity stress conditions in isolated LHC IIb, showed a significant increase at 600 mM NaCl in the non-inoculated _H. portulacoides_[39; 66; 67]. This can indicate an alleviation of the potential photoinhibition conditions due to bacterial inoculation, and thus a reduction of the photoprotective countermeasures. The chlorophyll _a/b_ ratio displayed a significant decrease with increasing NaCl concentrations in non-inoculated plants only. This may indicate that the absorbed rate of light energy exceeds the photochemical capability [43]. Additionally, at 0 mM and 400 mM NaCl, inoculated plants experienced an amelioration effect brought about by a significant increase in the total chlorophyll concentration. This can be explained by an enhanced nitrogen fixation capability found in the PGPR inoculate. Thus, an enhanced supply of nitrogen can be assumed that will stimulate the production of photoreceptor pigments [24; 68; 69]. It is known that salinity-induced stress can cause the accumulation of harmful molecules in plant tissues. An excess of Na\({}^{+}\) ions in the cytoplasm has a negative influence on the uptake of other ions. This can ultimately lead to the impairment of various metabolic pathways paralleled by increased production of reactive oxygen species (ROS) [68; 70]. To counteract this latter effect, halophytes build up effective antioxidative mechanisms, as proficient enzyme-based systems as well as mechanisms driven by pigment conversions [71; 72]. When assessing the oxidative stress biomarkers, equilibrated response tendencies to the salt gradient were found, but some noteworthy PGPR induced discrepancies were seen between the treated groups. Non-inoculated and inoculated plants showed a catalase (CAT) activity and ascorbate peroxidase (APx) activity reduction through increasing salinities; however, at 400 mM NaCl, catalase displayed significantly higher activity in the non-inoculated samples, possibly due to the also significantly higher uptake of Na\({}^{+}\) in the leaves [73; 74]. On the other hand, at 600 mM NaCl, superoxide dismutase (SOD) and ascorbate peroxidase activity, in non-inoculated individuals, were shown to be higher, pointing to a higher H\({}_{2}\)O\({}_{2}\) production by SOD and subsequent metabolization by APx [75]. Nevertheless, the significant increase of lipid peroxidation products (TBARS) found in the same group suggests that in non-inoculated _H. portulacoides_ when exposed to 600 mM NaCl, the peroxidase metabolization might not be sufficient with a consequent higher ROS production and lower ROS scavenging mechanisms [74]. In summary, from the analysis of provided data, it can be proposed that root inoculation by the chosen PGPR consortium resulted in a significant amelioration effect. Phytoprotection and overall improved fitness of _H. portulacoides_ were observed when exposing the plants to mild NaCl stress.