## 3 Discussion
The Extent of Bacterial Stimulation Effect in Roots and Shoots Varies Depending on the Temperature Condition  
The modulation of the growth that was induced by PsJN on Arabidopsis varied in intensity between the two temperatures that were investigated in our study. Although the beneficial effects of the bacteria were significant under the ambient condition on the root tissues, these effects were more substantial, with there being higher relative differences between the inoculated and non-inoculated types under the heat-stress conditions (Figure 2). For example, at the end of the growing period, the difference in the root lengths of the inoculated and non-inoculated plants under the heat stress condition based on individual root parts was about 3.5 times higher than it was in the primary roots, 3.8 times higher in the 1 st-order laterals, and about higher 2.1 times in the 2 nd-order laterals than it was in the ambient condition. The strain PsJN is already known for its plant-growth promotion benefits under normal conditions; however, plants can take even more advantage of this bacteria's imparted traits under stressful high-temperature situations when the impacts can be quite deleterious to the plants. For example, in potatoes, a high temperature caused a reduction in the root and shoot development, the number of potato tubers, and the fresh weight of them, however, the PsJN inoculation showed noticeable beneficial effects on the root biomass, and significantly enhanced the number of tubers and the weight of some cultivars [35]. The thermotolerant capability that was imparted by the bacteria might be attributed to its production of ACC deaminase, which has been linked with the alleviation of plant stress because of its contribution in lowering the ethylene levels, thereby promoting plant growth [37; 88]. ACC deaminase-producing bacteria enhance the plants' growth under different biotic and abiotic environmental conditions such as pathogen attacks, drought, salinity, and organic and inorganic contaminants [1; 89]. Furthermore, microbial deaminases have been shown (or proposed) to be responsible for the dissociation of stress-induced ACC (secreted as root exudates) into ammonia and \(\alpha\)-ketobutyrate, thereby eliminating ACC, the precursor for ethylene that has a drastic impact on the physiology, growth, and development of plants [90; 91; 92]. Under periods of stresses, ethylene can facilitate the early senescence and abscission of various organs, which are mechanisms to conserve resources [93; 94]. The role of microbial ACC deaminase producers such as PsJN might be immensely important in today's agricultural systems, where stressed-induced ethylene changes in crops are aggravated by increasing temperature conditions. Although the PGP effects of the bacteria were strongly demonstrated on several root parameters such as the root lengths and the growth rates (total, primary, and 1 st- and 2 nd-order laterals), as well as the number of 1 st- and 2 nd-order lateral roots, these results did not translate in the root system traits (Figure 3a-d). The conditions in agar where the water and nutrients are homogenized are different from they are in the soil where there is a need to expand the volume that is covered by the roots as there will be a very likely heterogenous distribution of the edapnic resources. Still, we could show that PsJN causes spatial distribution effects (Figure S3), and that the bacterial enhancements for improved nutrient uptake were manifested in the individual root component, e.g., the longer lateral roots (Figure 2), and in the changed root length distribution, e.g., an increased root density at the deeper part the roots (Figure 4).