Cyanobacteria Increase the Activity of Enzymes Involved in the Lignin Biosynthesis Pathway in Thymus vulgaris L.

The effects of plant inoculation with plant growth-promoting cyanobacteria on the activity of phenylalanine ammonia-lyase (PAL), peroxidase (POD), and cell wall POD enzymes in Thymus vulgaris L. were investigated. A greenhouse experiment with five replications was carried out using inoculation of five cyanobacteria suspensions (2.5%) including Anabaena torulosa ISB213, Nostoc calcicola ISB215, Nostoc ellipsosporum ISB217, Trichormus doliolum ISB214 and Oscillatoria sp. ISB2116 on T. vulgaris plants. After four months, the plants were harvested, and the enzyme levels were measured. The statistical analysis revealed that the treatment with N. ellipsosporum ISB217 had the most significant impact on PAL enzyme activity in the treated plants. Compared to the control group (0.13 ± 0.002), the plants treated with T. doliolum ISB214 exhibited the highest activity of POD (0.69 ± 0.03) enzyme and cell wall POD (0.53 ± 0.05). Also, the amount of lignin in the treated plants had a significant increase compared to the control. Considering the valuable medicinal properties of the secondary metabolites found in thyme plants and the crucial role of nutritional management in enhancing the production and quality of this medicinal plant. The usage of appropriate growth stimulants has the potential to enhance the biosynthesis of these compounds. This study demonstrated that application of microalgae extract as a completely natural and eco-friendly substance by increasing the enzymes activity related to the synthesis of cell wall materials can boost the resistance of plants against biotic and abiotic stresses.