Book ChapterDOI
How the Plant Growth-Promoting Bacterium Azospirillum Promotes Plant Growth—A Critical Assessment
Yoav Bashan,Luz E. de-Bashan +1 more
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This review proposes the “Multiple Mechanisms Theory,” based on the assumption that there is no single mechanism involved in promotion of plant growth by Azospirillum, but a combination of a few or many mechanisms in each case of inoculation.Abstract:
During the last 35 years of studies of Azospirillum–plant interaction, over 20 proposals were suggested for the mechanism of action by which Azospirillum spp., the most intensively studied plant growth-promoting bacteria, enhances plant growth. The proposals include a single phytohormone activity, multiple phytohormones, nitrogen fixation, assortments of small-sized molecules and enzymes, enhanced membrane activity, proliferation of the root system, enhanced water and mineral uptake, mobilization of minerals, mitigation of environmental stressors of plants, and direct and indirect biological control of numerous phytopathogens. By volume, the largest number of published information involves hormonal activities, nitrogen fixation, and root proliferation. After analyzing the accumulated knowledge, it was concluded that this versatile genus possesses a large array of potential mechanisms by which it can effect plant growth. Consequently, this review proposes the “Multiple Mechanisms Theory,” based on the assumption that there is no single mechanism involved in promotion of plant growth by Azospirillum, but a combination of a few or many mechanisms in each case of inoculation. These may vary according to the plant species, the Azospirillum strain, and environmental conditions when the interaction occurred. The effect can be cumulative, an “additive hypothesis” (proposed before), where the effects of small mechanisms operating at the same time or consecutively create a larger final effect on plant. Additionally, the observed effect on plant growth can be the result of a tandem or a cascade of mechanisms in which one mechanism stimulates another, yielding enhanced plant growth, such as the plausible relations among phytohormones, nitric oxide, membrane activities, and proliferation of roots. Finally, the growth promotion can also be a combination of unrelated mechanisms that operate under environmental or agricultural conditions needed by the crop at particular locations, such as mitigating stress (salt, drought, toxic compounds, adverse environment), and the need for biological control of or reducing pathogenic microflora.read more
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Journal ArticleDOI
Plant growth-promoting rhizobacteria (PGPR): emergence in agriculture
TL;DR: The progress to date in using the rhizosphere bacteria in a variety of applications related to agricultural improvement along with their mechanism of action with special reference to plant growth-promoting traits are summarized and discussed in this review.
Journal ArticleDOI
The Hidden World within Plants: Ecological and Evolutionary Considerations for Defining Functioning of Microbial Endophytes
Pablo R. Hardoim,Leonard S. van Overbeek,Gabriele Berg,Anna Maria Pirttilä,Stéphane Compant,Andrea Campisano,Matthias Döring,Angela Sessitsch +7 more
TL;DR: This review addresses the concept of endophytism, considering the latest insights into evolution, plant ecosystem functioning, and multipartite interactions.
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Agricultural uses of plant biostimulants
TL;DR: There is growing scientific evidence supporting the use of biostimulants as agricultural inputs on diverse plant species, such as increased root growth, enhanced nutrient uptake, and stress tolerance.
Journal ArticleDOI
Plant growth-promoting rhizobacteria and root system functioning.
Jordan Vacheron,Guilhem Desbrosses,Marie-Lara Bouffaud,Bruno Touraine,Yvan Moënne-Loccoz,Daniel Muller,Laurent Legendre,Florence Wisniewski-Dyé,Claire Prigent-Combaret +8 more
TL;DR: Novel knowledge and gaps on PGPR modes of action and signals are addressed, recent progress on the links between plant morphological and physiological effects induced by PGPR are highlighted, and the importance of taking into account the size, diversity, and gene expression patterns of PGPR assemblages in the rhizosphere to better understand their impact on plant growth and functioning is shown.
Journal ArticleDOI
Advances in plant growth-promoting bacterial inoculant technology: formulations and practical perspectives (1998–2013)
TL;DR: Practical aspects of bacterial inoculants for contemporary agriculture and environmental restoration is critically evaluated from the point of view of their current technological status, current applications, and future use.
References
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Journal ArticleDOI
Drought and Salt Tolerance in Plants
TL;DR: The responses of plants to salt and water stress are described, the regulatory circuits which allow plants to cope with stress are presented, and how the present knowledge can be applied to obtain tolerant plants is discussed.
Journal ArticleDOI
Indole-3-acetic acid in microbial and microorganism-plant signaling.
TL;DR: The fact that bacteria use this phytohormone to interact with plants as part of their colonization strategy, including phyto-stimulation and circumvention of basal plant defense mechanisms, is highlighted.
Journal ArticleDOI
Integration of plant responses to environmentally activated phytohormonal signals.
Patrick Achard,Hui Cheng,Liesbeth De Grauwe,Jan Decat,Hermien Schoutteten,Thomas Moritz,Dominique Van Der Straeten,Jinrong Peng,Nicholas P. Harberd +8 more
TL;DR: The nuclear-localized growth-repressing DELLA proteins of Arabidopsis integrate responses to independent hormonal and environmental signals of adverse conditions to permit flexible and appropriate modulation of plant growth in response to changes in natural environments.
Journal ArticleDOI
Bacterial biosynthesis of indole-3-acetic acid
C L Patten,Bernard R. Glick +1 more
TL;DR: The role of bacterial IAA in the stimulation of plant growth and phytopathogenesis is considered and several different IAA biosynthesis pathways are considered.
Journal ArticleDOI
Plant Growth-Promoting Effects of Diazotrophs in the Rhizosphere
TL;DR: It is now clear that associative diazotrophs exert their positive effects on plant growth directly or indirectly through (a combination of) different mechanisms, and further elucidation of the different mechanisms involved will help to make associative Diazotrophic bacteria a valuable partner in future agriculture.
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