## 3 Discussion
The timing and location of the emergence of these lateral roots also contributed to the density and distribution of the roots across different depths and to means by which the application of the bacteria affects the total root lengths (Figure 4a-c). The increase in the root length distribution towards the deeper or distal part of the root system by the bacteria PsJN indicates the potential for more water and nutrient foraging when the upper adaphic environment has become unfavorable for the roots. When they were compared to the primary roots that traced their origin back from embryogenesis, the lateral roots form post-embryonically, allowing for the dynamic acclimation of the whole root system architecture to environmental fluctuations over time [52; 84]. The strong correlation between the number of 1 st-order laterals against the increase in both the length of the primary roots and the number of 2 nd-order laterals (Figure 5a,b) that underwent inoculation indicates the stimulatory effect of the PsJN bacteria on the growth of these roots at an ambient condition. This suggests one of PsJN's adaptation benefits to the plants. The increase in the number of lateral roots does not only widen the root scavenging area [85], but this also provides a crucial adaptive response to elevated temperatures, which is generally accompanied by a reduced availability of water and nutrients in field settings. Early vigor of these root types can provide an advantage for seedling establishment in preparation for the later growth stages and environmental challenges [86]. Positive Bacteria-Imparted Root Modifications Correlate with Shoot Responses at Ambient Temperature and Are Time-Dependent  
The positive effects of PsJN on the morphology and growth dynamics of the individual root types manifested early during the root development, before declining after certain time points (Figure 4). This trend of initial bacterial stimulation and decline was exhibited mainly by the primary and 1 st-order lateral roots. On the other hand, the 2 nd-order lateral roots showed a continuous increase from the moment that the inoculation was performed, which can be ascribed to the late development of these root types. Contrary to the early growth promotion that was imparted by PsJN in the roots, which started at 5 DAI, the enhancement of the rosette surface area of the shoot came 14 days later (Figure 6a) under the ambient conditions. An extended time-series measurement might be needed to fully elucidate the potential of the bacteria PsJN for both the root (2 nd-order laterals) and shoot improvement as our growth system was limited by the size of the plates. Whilst they can be found in the aboveground tissues of the plants, the rhizosphere bacteria _P. phytofilmans_ PsJN generally reside inside the root tissues, although some are also located in the rhizplane [87]. Since the plants usually first invest in root growth at the early establishment stage [63], the growth promotion that is imparted by the PGPR strain PsJN may also be reflected in these growing root components. The late-stage significant enhancement of the rosette surface area by the bacteria may just be following this growth trend. It may also be that the plant growth promotion in the shoot is not (only) through the increase in the rosette surface area, but it is also from other shoot traits such as the growth rates and the number of rosette leaves [46]. The results of measurements of the shoot dry weights at the point of harvesting them (21 DAI) indicate that there was a strong bacterial stimulation effect, with the inoculated plants being about 25% heavier than the control plants were under the ambient temperature (Figure 6b). This observed increase in the shoot dry matter could be explained by the stimulation of the primary root growth and root branching [83], which consequently lead to better nutrient and water uptake. This may indicate that the benefit of using PsJN will potentially transfer to the shoot biomass, and it will be useful for agriculture.