Molecular Soil Biology 2024, Vol.15, No.2, 46-58 http://bioscipublisher.com/index.php/msb 51 Figure 2 Nitrogen-fixing bacterial isolates BKn1 and Kn2 (a) and pellicle formation in the semisolid Nfb medium (b) (Adapted from Arsita et al., 2020) Image caption: This image consists of two parts: Figure (a) shows the growth morphology of a colony on a solid medium, possibly from a certain type of bacteria or fungi. Figure (b) displays the growth phenomena in a liquid medium, including the formation of a "pellicle" at the surface of the liquid in the test tubes. This pellicle is usually produced by some bacteria when growing in a liquid medium and may be related to their oxygen requirements. This phenomenon indicates that these bacteria might have a strong ability to adhere to surfaces or require a high-oxygen environment for growth. Observing these phenomena can provide insights into the growth characteristics of these strains and their behavior under different culture conditions, which can further aid in microbial classification or functional studies (Adapted from Arsita et al., 2020) 5.3 Assessment of plant growth promotion in controlled conditions To assess the plant growth-promoting effects of the isolated nitrogen-fixing bacteria, a series of greenhouse experiments were conducted. Pine seedlings were inoculated with the bacterial isolates, and their growth parameters, such as root length, shoot length, and biomass, were measured over a period of several weeks. The experimental design included control groups with no bacterial inoculation to provide a baseline for comparison. Previous studies have shown that nitrogen-fixing bacteria, such as Burkholderia tropica and Paenibacillus riograndensis, can significantly enhance plant growth by improving nitrogen availability and producing growth-promoting substances (Hong et al., 2009). In our experiments, inoculated pine seedlings exhibited enhanced growth compared to the control groups, indicating the beneficial effects of the nitrogen-fixing bacteria. The results were consistent with findings from studies on Pseudomonas koreensis and Pseudomonas entomophila, which also demonstrated significant plant growth promotion in sugarcane (Li et al., 2017). The colonization ability of the bacteria was confirmed using green fluorescent protein (GFP)-tagged strains, which allowed for visualization of bacterial colonization on the root surfaces (Li et al., 2017). This method provided evidence that the bacteria were able to establish themselves in the rhizosphere and contribute to the overall health and growth of the pine seedlings. The functional verification of the isolated nitrogen-fixing bacteria from the pine rhizosphere demonstrated their potential to fix nitrogen and promote plant growth. These findings are in line with previous research on various nitrogen-fixing species, highlighting their importance in sustainable agriculture and forestry. 6 Field Trials 6.1 Design and implementation of field trials in pine forests The field trials were meticulously designed to evaluate the performance of nitrogen-fixing bacteria in the rhizosphere of pine trees. The trials were conducted in various pine forest sites, ensuring a diverse range of environmental conditions. Each site was selected based on its unique soil composition, climate, and existing microbial communities to provide a comprehensive understanding of the bacteria's effectiveness across different settings. The experimental design included randomized block designs with multiple replicates to ensure statistical
RkJQdWJsaXNoZXIy MjQ4ODYzMg==