Document Type : Research Paper
Authors
1
MSc Student in Agronomy- Crop Ecology, Department of Plant Production and Genetics, Faculty of Agriculture, Shahid Bahonar University of Kerman, Iran.
2
Department of Plant Production and Genetics, Faculty of Agriculture, Shahid Bahonar University of Kerman, Iran.
3
Department of Agronomy and Plant Breeding, College of Agriculture, Shahid Bahonar University of Kerman ,Kerman-Iran
Abstract
Background and Objective: Glycyrrhiza glabra L., commonly known as licorice is a perennial medicinal plant, which possesses multiple health benefits. Licorice root extract can be used for traditional medicine and food and pharmaceutical industries since it contains bioactive compounds and main ingredients, glycyrrhizin, liquiritin, and glabridin. The utilization of plant growth-promoting rhizobacteria as biofertilizers is increasingly being suggested as a way to reduce the application rate of chemical fertilizers in agricultural systems. Therefore, the aim of this study was to assess the impact of Azotobacter as one of the plant growth-promoting bacteria alone and in combination with a reduced application rate of chemical fertilizer on photosynthesis, gas exchange, and biomass production of licorice plants propagated through seeds and rhizomes.
Materials and Methods: A field experiment was conducted by inoculating the seeds and rhizomes of licorice plants with Azotobacter chroococcum (Ac; strain 1087) alone or in combination with reduced level of chemical fertilizer. The five treatments for the experiment were (i) control (no inoculation and fertilization) (ii) Ac inoculation; (iii) 100% recommended N (100% N) (iv) 50% recommended N (50% N); and (v) Ac inoculation + 50% N which were evaluated in both propagation methods (seeds and rhizomes). Net photosynthesis rate, leaf transpiration rate, intracellular CO2, photosynthetic water use efficiency, chlorophyll content (SPAD value), plant height, leaf area, and shoot, root, and rhizome dry weight, and total biomass production (root + rhizome) were measured.
Results: The observed results revealed that the licorice plants produced from the rhizomes showed an increase in plant height by 75%, a four-fold increase in the leaf area, a nine-fold increase in the shoot dry weight, a 6.6-fold increase in each rhizome weight, and increase of 23-fold, 7.3-fold, and 11.1-fold in production of the rhizome, root, and total biomass respectively, compared with the plants produced from seeds. The findings also showed that Ac inoculation further influenced root and rhizome biomass production more than vegetative growth-related parameters and shoot biomass production. Integrated inoculation of Ac with 50% N applied, interestingly, improved the plant shoot dry weight by 134 and 147% and total biomass production by 149 and 94% through improving the leaf area by 180 and 114%, SPAD value by 13 and 9%, net photosynthesis rate by 119 and 15%, and water use efficiency by 43 and 42% in plants resulted from rhizomes and seeds, respectively. Moreover, results demonstrated that simultaneous inoculation of Ac and the application of 50% N showed similar results compared with the application of 100% N.
Conclusion: These findings suggest that inoculation of A. chroococcum integrated with a reduced dose of urea can reduce the amount of nitrogen fertilization up to 50% without significantly reducing the yield of licorice produced through seeds and rhizomes. The results of this study also showed that the licorice produced from the rhizomes showed a multifold increase in various growth and yield traits compared to the licorice obtained from the seed during the first growing year. This can be considered in the production of licorice plants in different conditions, based on different production aspects.
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