Plant-bacteria symbiosis is another important aspect of modern agriculture and a promising method for addressing the aforementioned problems. Leguminous plants, such as peas and beans, can establish symbiosis with soil bacteria, particularly of the Rhizobium genus. This allows plants to efficiently utilize atmospheric nitrogen. Molecular signals known as Nod factors, produced by these bacteria, are crucial for initiating symbiosis and stimulating the development of root nodules. This symbiosis works on a simple principle: leguminous plants provide a source of carbon to the soil bacteria through photosynthesis products, while the bacteria supply the plants with readily available nitrogen for optimal growth. It is a unique process in which bacteria, after transforming their cells into bacteroids, can reduce nitrogen from the air (which is normally inaccessible) into easily assimilable ammonia, which is later reduced to nitrate ions .
A few words about Nod factors
The mutual recognition of symbiotic partners is based on the exchange of specific molecular signals from plants and bacteria. Plant roots secrete a group of organic compounds called flavonoids, to which rhizobia respond by producing lipochitooligosaccharides (known as Nod factors) . These factors are key signaling molecules that initiate symbiotic interactions and are necessary for establishing effective symbiosis between rhizobia and leguminous plants . They activate cell division by regulating plants’ auxin levels (a growth hormone). Nod factors have been proven to influence many processes in plants, such as seed germination, root branching, and shoot growth stimulation .
An incredible patent by Polish scientists
The collaboration between scientists from Maria Curie-Skłodowska University in Lublin (UMCS) and the Institute of Soil Science and Plant Cultivation – State Research Institute in Puławy (IUNG) has enabled the isolation of key factors that influence the initiation and development of root nodules in plants (Nod factors) .
It is worth explaining the innovation of this patent. Traditionally, research on Nod factors focused on studying their impact only on plants that naturally exhibit the ability to symbiotically interact with bacteria of the Rhizobium genus. Many years of research have shown that externally added Nod factors positively affect the growth and development of leguminous plants, with reduced nitrogen fertilizer requirements . The research associated with the patent investigated the effects of these isolated factors on other types of cultivated plants.
Nod factors are not traditionally considered growth-promoting factors for plants that do not form root nodules, such as oilseed plants. One study based on the patent  focused on evaluating the influence of purified Nod factors on rapeseed (Brassica napus L.), which is considered the most important oilseed crop in the world. The use of bacterial Nod factors resulted in increased stem density, thereby providing greater resistance to lodging. The results also indicated potential increases in resistance to infections and attacks by insects. The mechanism behind the enhancement of these defense systems was linked to an increased level of quercetin and kaempferol derivatives (flavonoids) in the plants treated with the biological fertilizer compared to the control plants.
The application of the patented method is not limited to a single plant species. Studies have shown the effectiveness of Nod factors in various cultivated plants, such as peas, vetch, and corn . Further research in this field may lead to the development of new fertilization strategies that utilize the properties of Nod factors, contributing to more sustainable and efficient crop production without the need for synthetic fertilizers. This is an important step toward sustainable agriculture, aiming to provide an adequate food supply for a growing population while minimizing the impact on the natural environment.
Trivia (fun fact)
Did you know that in Poland, devastated and degraded lands make up 2% of the total, and the area of reclaimed lands is increasing every year (1,476 hectares in 2020 and 2,236 hectares in 2021)? 
 Susniak, K.; Krysa, M.; Kidaj, D.; Szymanska-Chargot, M.; Komaniecka, I.; Zamlynska, K.; Choma, A.; Wielbo, J.; Ilag, L.L.; Sroka-Bartnicka, A. Multimodal Spectroscopic Imaging of Pea Root Nodules to Assess the Nitrogen Fixation in the Presence of Biofertilizer Based on Nod-Factors. Int. J. Mol. Sci. 2021, 22, 12991. https://doi.org/10.3390/ijms222312991
 Oldroyd, Giles ED, and J. Allan Downie. “Coordinating nodule morphogenesis with rhizobial infection in legumes.” Annu. Rev. Plant Biol. 59 (2008): 519-546.
. Tanaka, Kiwamu, et al. “Effect of lipo-chitooligosaccharide on early growth of C4 grass seedlings.” Journal of Experimental Botany 66.19 (2015): 5727-5738.
 Rocznik Statystyczny Rolnictwa 2022. Główny Urząd Statystyczny. https://stat.gov.pl/obszary-tematyczne/roczniki-statystyczne/roczniki-statystyczne/rocznik-statystyczny-rolnictwa-2022,6,16.html
 Krysa, M.; Susniak, K.; Kubas, A.; Kidaj, D.; Sroka-Bartnicka, A. MALDI MSI and Raman Spectroscopy Application in the Analysis of the Structural Components and Flavonoids in Brassica napus Stem. Metabolites 2023, 13, 687. https://doi.org/10.3390/metabo13060687