Role of Melatonin and Plant‐Growth‐Promoting Rhizobacteria in the Growth and Development of Plants

Abstract

Melatonin is a tryptophan‐based indole molecule found in primitive photosynthetic bacteria to mammals. It performs different functions in plants like rhizogenesis, enhancing plant growth, seed germination, plant yield, biomass production, photosynthesis, circadian rhythm, and fruit ripening. In addition, one of the most significant attributes of melatonin is its antioxidant activity. Moreover, it works as an anti‐stress agent against different biotic and abiotic stresses like drought, salinity, potentially toxic metals, and pathogens. Melatonin forms antioxidant cascade reaction by scavenging free radicals that enhances its antioxidant capacity. In response to different stress conditions, expression of genes involved in melatonin synthesis is increased. In the same way, plant‐growth‐promoting rhizobacteria colonize plant roots and enhance plant growth by a number of mechanisms like phosphate solubilization, nitrogen fixation, siderophore production, production of phytohormones, phytoremediation, disease suppression, and production of 1‐aminocyclopropane‐1‐carboxylate deaminase. Thus, melatonin and plant‐growth‐promoting rhizobacteria are involved in enhancing plant growth under abiotic and biotic stress but the mechanisms of action of both are different. Therefore, in this study, the data on the impact of melatonin and plant‐growth‐promoting rhizobacteria on plants are combined for the first time and how these could be useful in enhancing the plant growth is examined. In addition, the research gaps are identified in melatonin and plant‐growth‐promoting rhizobacteria research already conducted from the last few decades that will help the scientific community in further research.

Melatonin and plant growth-promoting rhizobacteria alleviate the cadmium and arsenic stresses and increase the growth of Spinacia oleracea L.

“…Hahm et al (2017) also found a significant increase in plant height, fresh weight, dry weight, and chlorophyll contents in abiotic stressed pepper plants inoculated with Brevibacterium iodinum, Rickettsia massiliae, and Microbacterium oleivorans. PGPR stimulates plant growth and development by different processes, such as by increasing nutrient uptake, siderophores production, nitrogen fixation, phosphorus solubilisation, producing phytohormones, and producing secondary metabolites that work as insecticides (Asif et al 2019). Results of current studies show that there is a significant increase in root length, plant height, fresh weight, dry weight, and chlorophyll content in plants applied with melatonin or B. licheniformis without any metal treatment while metals treated plants with melatonin application or B. licheniformis application also enhanced physiological parameters and chlorophyll content significantly as compared to control.…”

“…The application of melatonin and PGPR in agriculture enhances plant growth under abiotic and biotic stress without disturbing the natural soil ecosystem. They both are non-toxic substances that increase and stimulate processes involved in plant growth and development (Asif et al 2019).…”

Melatonin: A master regulator of plant development and stress responses

“…In the past few decades, a series of studies have implicated melatonin as a pivotal molecule in root growth and development (Arnao and Hernández‐Ruiz, 2007, 2015; Pelagio‐Flores et al, 2012; Tan et al, 2012; Zhang et al, 2014b; Arnao and Hernández‐Ruiz, 2015; Wen et al, 2016; Liang et al, 2017; Chen et al, 2019). Furthermore, accumulating evidence suggests that melatonin also acts as a central component in the interaction of roots with microorganisms in the rhizosphere (Jiao et al, 2016; Ma et al, 2017; Asif et al, 2019).…”

Melatonin as Master Regulator in Plant Growth, Development and Stress Alleviator for Sustainable Agricultural Production: Current Status and Future Perspectives

“…It is biodegradable and safer to be used in organic farming. The excessive intake of melatonin in plants can prevent peroxidation of plant products due to its antioxidant nature and thus increase the shelf life of plants and improve crop yields [111,112]. The main component of plants is chlorophyll, so its preservation and photosynthetic stimulation is of great importance in crop improvement.…”