Cytokinin producing bacteria enhance plant growth in drying soil

Abstract

Cytokinins can promote stomatal opening, stimulate shoot growth and decrease root growth. When soil is drying, natural cytokinin concentrations decrease in association with stomatal closure and a redirection of growth away from the shoots to the roots. We asked if decreased cytokinin concentrations mediate these adaptive responses by lessening water loss and promoting root growth thereby favouring exploration for soil water. Our approach was to follow the consequences for 12-d-old lettuce seedlings of inoculating the growing medium with cytokininproducing bacteria under conditions of water sufficiency and deficit. Inoculation increased shoot cytokinins as assessed by immunoassay and mass spectrometry. Inoculation also promoted the accumulation of shoot mass and shortened roots while having a smaller effect on root mass. Inoculation did not raise stomatal conductance. The possible promoting effect of these cytokinins on stomatal conductance was seemingly hampered by increases in shoot ABA that inoculation also induced. Inoculation lowered root/shoot ratios by stimulating shoot growth. The effect was greater in non-droughted plants but remained sufficiently strong for shoot mass of inoculated droughted plants to exceed that of well-watered non-inoculated plants. We conclude that compensating for the loss of natural cytokinins in droughted plants interferes with the suppression of shoot growth and the enhancement of root elongation normally seen in droughted plants.

The Role of Soil Beneficial Bacteria in Wheat Production: A Review

“…The plants inoculated with cytokinin-producing bacteria B. subtilis showed the increased chlorophyll content and cytokinin accumulation, which led to the increase in weight of shoots and roots [90,91]. On the other hand, treatment of plant with a substance obtained from cytokinin-producing microorganisms, typically colonizing in wheat roots [92,93], increased chlorophyll content in leaf; in this case, the level of chlorophyll was comparable to that observed in the plants treated with a synthetic cytokinin benzyladenine.…”

Survey of Plant Drought-Resistance Promoting Bacteria from Populus euphratica Tree Living in Arid Area

“…Bacteria producing phytohormones such as auxins [2], cytokinins [9], gibberellins [10], and abscisic acid [11] were reported to improve the drought resistance of host plants. Several studies have identified PGPB which produce 1-aminocyclopropane-1-carboxylate (ACC) deaminase and decrease ethylene levels of host plants as a method of conferring drought resistance [12,13].…”

Cytokinins production by fluorescent Pseudomonas isolated from rhizospheric soils of Malus and Pyrus

“…Author(s) agree that this article remains permanently open access under the terms of the Creative Commons Attribution License 4.0 International License and its occurrence was observed in many terrestrial and rhizospheric soil (Kampert and Strzelcyk, 1984;Arkhipova et al, 2007;Hussain and Hasnain, 2009) which suggested that bacterial cytokinins may affect the growth and development of plants. Recent studies confirmed that, a number of bacterial species mostly associated with the plant rhizosphere, are found to be associated with cytokinins production including Flavobacterium, Acinetobacter, Bacillus, Arthrobacter, Aerobacter, Azospirillum and Pseudomonas sp.…”

“…Recent studies confirmed that, a number of bacterial species mostly associated with the plant rhizosphere, are found to be associated with cytokinins production including Flavobacterium, Acinetobacter, Bacillus, Arthrobacter, Aerobacter, Azospirillum and Pseudomonas sp. (Maruyama et al, 1986;Perig et al, 2007;Arkhipova et al, 2007;OrtizCastro et al, 2008). Cytokinins have key regulatory roles in plant growth and development.…”