Role of Cytokinins in Plant Growth Promotion by Rhizosphere Bacteria

Abstract

Abstract:Plant growth regulators (PGRs) are organic substances that influence the physiology and development of plants at very low concentrations. Cytokinins are one of the five major groups of PGRs or phytohormones and regulate cytokinesis in plant cells. Soil microorganisms are capable of synthesizing PGRs such as cytokinins in pure culture, soil and in association with plant tissues. This chapter reviews the structure and function of cytokinins in plant tissues and their production by plant growth promoting rhizobacteria (PGPR). A role for microbially-produced cytokinins in plant growth and development is proposed. Cytokinin production by PGPR is an innovative alternative to enhance plant growth and may be a sustainable approach to improve the yield and quality of agricultural crops. However further research is necessary to understand the principles underlying cytokinin production by rhizobacteria and to develop cytokinin-producing inoculants for practical application by growers.

Indole-3-acetic acid (IAA) production trait, a useful screening to select endophytic and rhizosphere competent bacteria for rice growth promoting agents

“…Since endophytic microbial communities originate from the soil and rhizosphere [16] , [17] , bacterial IAA can attract more rhizoshere bacteria by increasing more amount of root exudation. Since bacterial IAA stimulates the development of the root system of the host plant [18] , IAA producing isolates can improve the fitness of plant-microbe interactions [18] , [19] . It is known that bacterial IAA can loosen plant cell walls and as a result promotes an increasing amount of root exudation that provides additional nutrients to support the growth of rhizosphere bacteria [12] , [13] .…”

“…Since endophytic microbial communities originate from the soil and rhizosphere [16] , [17] , bacterial IAA can attract more rhizoshere bacteria by increasing more amount of root exudation. Since bacterial IAA stimulates the development of the root system of the host plant [18] , IAA producing isolates can improve the fitness of plant-microbe interactions [18] , [19] .…”

Mining Halophytes for Plant Growth-Promoting Halotolerant Bacteria to Enhance the Salinity Tolerance of Non-halophytic Crops

“…CK production is a relatively common trait of PGPRs (Dodd et al, 2010 ). PGPRs can influence plant CK concentration by synthesizing CK or altering CK homeostasis in the plant (Arshad and Frankenberger, 1991 ; de Garcia Salamone et al, 2005 ; Glick, 2012 ; Pallai et al, 2012 ; Kapoor and Kaur, 2016 ). The Platycladus orientalis plants inoculated with a CK-producing PGPR strain B. subtilis had increased CK levels in the shoots and were more resistant to drought (Liu et al, 2013 ).…”

Potential Role and Utilization of Plant Growth Promoting Microbes in Plant Tissue Culture

“…These phytohormones increase roots length of P. strombulifera , allowing them to explore the soil in depth and absorb more water. In hydroponic media, De Garcia Salamone et al (2005) compared Phaseolus vulgaris plants treated with auxin and cytokinin to those inoculated with Rhizobium. They noticed that the results in terms of growth were similar and the PGRs were detected in the medium of inoculated plants but not in the medium of non-inoculated roots.…”