## 3 Results and Discussion
### Physiological Ability and Functionality Study
#### 3.2.4. Phytohormone Production  
UPMC1166, UPMC1168, UPMC1254 and UPMC1389 have the potential to produce IAA (Table 3). These four isolates exhibited a positive interaction by the development of pink color (Figure 4).  
IAA synthesis is a key plant growth-boosting feature in PGPRs and a signal molecule in plant regulations [76]. Auxin regulates various activities in tissue culture, including tryp responses to gravity and light, organ patterning, shoot architecture, general root, and vascular growth [70]. A higher auxin level weakens plant defensive mechanisms, enhancing responses of long-term (cell division) and short-term (cell elongation) in plants, and granting easier colonization in the plant cells.  
According to [PERSON] et al. [76], _Bacillus cereus_ strains WI 41 and WI 36 produced the highest IAA (30 \(\upmu\)g/mL), followed by _M. yunnensis_ WI 60 (28 \(\upmu\)g IAA/mL). [PERSON] et al. [76] found that numerous _Paenibacillus_ sp. and _Bacillus_ sp. created IAA in Luria Bertani broth, which agreed with [PERSON] et al. [77]. In ideal growth conditions, [PERSON] and [PERSON] [78] and [PERSON] et al. [79] reported IAA production by rhizobacteria in the range of 53.1 to 71.1 ppm, but [PERSON] [80] reported IAA synthesis in bacteria in the range of 2.09 to 33.28 \(\upmu\)mol/mL. [PERSON] and [PERSON] [81] reported that _Bacillus_ isolates produced IAA in levels ranging from 35 to 217 \(\upmu\)g/mL. Four major factors (cultural circumstances, the organism involved, substrate availability and growth stage) influence the IAA generation in different PGPR species and strains [82].  
Plant-associated bacteria generate phytohormones (including IAA, gibberellins, and cytokini) that could promote faster plant growth and have improved defensive mechanisms against abiotic and biotic stressors [83]. [PERSON] and [PERSON] [70] isolated and characterized the PGPRs associated with _Sacarum officinarum_. According to [PERSON] and [PERSON] [70], the PGPR isolates could stimulate plant development indirectly or indirectly. According to the data, F372 had the most phosphate solubilization strain (15 mg/L), while F271 had the highest IAA production (63 mg/L). As a result, they proposed that using specific PGPR isolates as inoculants could be advantageous to sugarcane farming.  
According to [PERSON] et al. [20], all nine bacterial isolates produced ammonia, solubilized tri-calcium phosphate, and IAA on Pikoskaya's nutrient agar petri plates. Except for _Agrobacterium tumefaciens_ CL5, all strains showed resistance to salt up to 4% NaCl (1% NaCl). Phosphate solubilization, and IAA production have also been reported in _A. tumifaciens_, _Burkholderia_ sp., _Bacillus_ sp. and _Pseudomonas_ sp. by [PERSON] et al. [55], _Pseudomonas_ sp. and _Burkholderia_ by [PERSON] et al. [84], and in _Azotobacter chrooccum_ by [PERSON] [85].  
In general, rhizobacteria release IAA, which increases lengths and root surface areas. This facilitates the absorption of nutrients from the soils. Additionally, rhizobacterial IAA weakens the cell walls of the plants so as to produce a surge in root exudation, and this  
Figure 4: Bacteria with ability to produce phytohormone. These four isolates showed the positive reaction by formation of pink color after interaction with Salkowasky reagent.  
could provide extra nutrient levels to sustain rhizosphere bacteria development [86]. In the oil palm study, the three major nutrients (potassium, phosphorus and nitrogen) were the important elements in vegetative growth and production. However, the application of added PGPR with chemical fertilizer could improve the soil nutrient conditions and help disease control [87,88].