## 4 Discussion  
Lentil is one of the earliest domesticated species and one of the most consumed pulses, especially in the Mediterranean territory. One of the key elements in enhancing lentil crop productivity and ensuring its successful adaptation is optimal P fertilization. As reported in other studies, low soil productivity in cultivated areas is frequently linked to P deficiency. Unlike nitrogen, which can be introduced into the soil through nitrogen-fixing bacteria in the roots of leguminous plants like lentil [40], atmospheric microbes cannot augment P availability. The incorporation of P in the soil has been noted to enhance the microbial population, biomass and the activity of certain enzymes in the soil, collectively contributing to an increase in soil respiration, which is a desirable soil trait for improving the overall soil productivity [41]. In the context of lentils, the addition of P in the right doses is essential to achieve the anticipated crop yield [42]. Vital biological activities such as nodulation, nitrogen fixation and nutrient absorbance from the soil and the environment of the rhizosphere all require P sufficiency [19]. Adequate P in soil promotes the lateral root length and the total root mass. This is one of the mechanisms that ensures lentil plants' adaptation to P deficiency conditions since the plants are forced to search for water and nutrients in deeper soil layers [43]. Figure 11: RT-qPCR showing the relative expression of F3\({}^{\prime}\)H, bHLH, DFR and DHM between the S1 and S2 and the S1 and S3 stages, using S1 as control, and between the S2 and S3 stages, using S2 as the control, in all three P treatments. In this study, the lower P treatment (P0) presented the highest number of unique and total DEGs. The differential expression analysis of genes did not demonstrate any particular clustering pattern in the different P treatments but revealed some groups of DEGs within noted areas in Figure 5's heatmap (Elements 1-5) that appear to be influenced by the level of P fertilization. The utilization of GO enrichment analysis and KEGG pathway analysis facilitated a comprehensive examination of these DEGs, and their expression patterns appear to be influenced by the different levels of P fertilization. Through the analysis, the involvement of the DEGs in specific biological processes and molecular functions was elucidated, thereby enhancing the scientific understanding of their functional roles. The genes of interest that were found within the highlighted regions (Elements 1-5) in Figure 5's heatmap, primarily fall within biological processes associated with macromolecule metabolism, nitrogen compound metabolism, biological regulation and localization. Their molecular functions encompass enzyme activities such as hydrolases, transferases and oxidoreductase, as well as roles such as transporter proteins and binding-associated functions. The analysis of DEGs possibly influenced by P levels yielded intriguing findings within more specific GOs, revealing genes closely associated with stress signaling, abiotic and biotic stress resistance, and gene and protein regulation. Terms that evidently support the genes' connection to stress signaling are \"signal transduction\" (GO:0007165), \"response to biotic stimuli\" (GO:0009607), \"cellular response to stress\" (GO:0033554), and \"heat shock protein binding\" (GO:0031072). Plant heat shock proteins are widely recognized for their crucial role in enhancing abiotic and biotic stress tolerance, which constitutes an integral part of the plant's defense mechanism [44]. According to the bibliography, in low P conditions, plants activate certain signaling and stress-related pathways that include the expression of phosphatases, MAP kinase, protein kinases, purple acid phosphatases (PAPs), S-glutathione transferases and the PHT1 family, which is comprised of phosphate transporters in order to improve P transport and utilization [45]. The term \"pyrophosphate activity\" (GO:0016462) is linked to plant growth, development and stress tolerance.