The Use of PGPB to Promote Plant Hydroponic Growth

Abstract

Improvements to the world’s food supply chain are needed to ensure sufficient food is produced to meet increasing population demands. Growing food in soilless hydroponic systems constitutes a promising strategy, as this method utilizes significantly less water than conventional agriculture, can be situated in urban areas, and can be stacked vertically to increase yields per acre. However, further research is needed to optimize crop yields in these systems. One method to increase hydroponic plant yields involves adding plant growth-promoting bacteria (PGPB) into these systems. PGPB are organisms that can significantly increase crop yields via a wide range of mechanisms, including stress reduction, increases in nutrient uptake, plant hormone modulation, and biocontrol. The aim of this review is to provide critical information for researchers on the current state of the use of PGPB in hydroponics so that meaningful advances can be made. An overview of the history and types of hydroponic systems is provided, followed by an overview of known PGPB mechanisms. Finally, examples of PGPB research that has been conducted in hydroponic systems are described. Amalgamating the current state of knowledge should ensure that future experiments can be designed to effectively transition results from the lab to the farm/producer, and the consumer.

The Role of Plant Growth-Promoting Microorganisms (PGPMs) and Their Feasibility in Hydroponics and Vertical Farming

“…Most modern hydroponic systems are categorized into seven main types (wicking systems, ebb and flow (flood and drain), drip irrigation, nutrient film technique (NFT), deep water cultures, aeroponics, and aquaponics) based on the application of nutrient solutions and the plant root system [ 83 ]. While a soil system supports the plants’ growth environment via PGPM colonization, and other lower-order animals, such as earthworms, that help in nutrient cycling [ 84 ], a hydroponic system provides a controlled and optimum environment to extract higher antioxidant contents in comparison to a soil-based system [ 85 ].…”

Perspectives on the Use of Biopolymeric Matrices as Carriers for Plant-Growth Promoting Bacteria in Agricultural Systems

“…Soil microbial diversity is influenced by a myriad of variables, including plant cover. The large variety of compounds released into the soil through plant roots provide nutrients for the microorganisms living in the root vicinity, creating a distinct site from the bulk soil referred to as the rhizosphere, which comprises the volume of soil surrounding plant roots [ 13 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ]. PGPB are nonpathogenic microorganisms that are natural soil inhabitants and are enriched in the rhizosphere.…”

“…PGPB are nonpathogenic microorganisms that are natural soil inhabitants and are enriched in the rhizosphere. They can colonize plant internal compartments and surfaces, establishing mutualistic relationships with the host plant that result in several beneficial effects for both partners [ 24 , 25 , 26 , 27 , 28 , 29 , 30 ].…”

“…The most studied abiotic stress conditions are drought and salinity [ 3 , 4 , 10 , 11 , 13 , 24 , 25 , 26 , 27 ]. PGPB can positively affect plant development through direct or indirect mechanisms [ 13 , 24 , 25 , 26 , 28 , 29 ].…”

“…Bacterial ACC deaminase helps plants reduce many of the symptoms related to stress exposure by reducing endogenous ethylene synthesis. In general, phytohormones produced by PGPB play an interdependent role in the integration of signaling pathways involved in the modulation of plant metabolism to a given environmental condition [ 3 , 4 , 13 , 24 , 25 , 26 , 29 ].…”