Root Exudates And Rhizosphere Effects Pdf
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- Root Exudates as Determinant of Rhizospheric Microbial Biodiversity
- Root Exudates Induce Soil Macroaggregation Facilitated by Fungi in Subsoil
- Rhizosphere interactions: root exudates, microbes, and microbial communities
Shengjing Shi, Alan E.
Root Exudates as Determinant of Rhizospheric Microbial Biodiversity
These metrics are regularly updated to reflect usage leading up to the last few days. Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts. The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric. Find more information on the Altmetric Attention Score and how the score is calculated. Despite reports in the literature of superior contaminant degradation in the root-zone of plants, this phenomenon, known as the rhizosphere effect, is poorly understood.
Root exudation is an important process determining plant interactions with the soil environment. Many studies have linked this process to soil nutrient mobilization. Yet, it remains unresolved how exudation is controlled and how exactly and under what circumstances plants benefit from exudation. The majority of root exudates including primary metabolites sugars, amino acids, and organic acids are believed to be passively lost from the root and used by rhizosphere-dwelling microbes. In this review, we synthetize recent advances in ecology and plant biology to explain and propose mechanisms by which root exudation of primary metabolites is controlled, and what role their exudation plays in plant nutrient acquisition strategies. Specifically, we propose a novel conceptual framework for root exudates. This framework is built upon two main concepts: 1 root exudation of primary metabolites is driven by diffusion, with plants and microbes both modulating concentration gradients and therefore diffusion rates to soil depending on their nutritional status; 2 exuded metabolite concentrations can be sensed at the root tip and signals are translated to modify root architecture.
Plant rhizosphere is the soil nearest to the plant root system where roots release large quantity of metabolites from living root hairs or fibrous root systems. These metabolites act as chemical signals for motile bacteria to move to the root surface but also represent the main nutrient sources available to support growth and persistence in the rhizosphere. Some of the microbes that inhabit this area are bacteria that are able to colonize very efficiently the roots or the rhizosphere soil of crop plants. These bacteria are referred to as plant growth promoting rhizobacteria PGPR. They fulfil important functions for plant growth and health by various manners. Diverse mechanisms are involved in the suppression of plant pathogens, which is often indirectly connected with plant growth. This paper describes the different mechanisms commonly used by most PGPR in their natural habitats to influence plant-growth and health.
Root Exudates Induce Soil Macroaggregation Facilitated by Fungi in Subsoil
Root exudates represent an important source of nutrients for microorganisms in the rhizosphere and seem to participate in early colonization inducing chemotactic responses of rhizospheric bacteria. We characterized the root exudates collected from rice plantlets cultured under hydroponic conditions and assessed their effects on the chemotaxis of two strains of endophytic bacteria, Corynebacterium flavescens and Bacillus pumilus , collected from the rice rhizosphere. We compared these chemotactic effects on endophytic bacteria with those on two strains of plant-growth-promoting bacteria, Azospirillum brasilense isolated from the corn rhizosphere and Bacillus sp. The root exudates were collected at different time intervals. The highest concentration and diversity of amino acids and carbohydrates were found during the first 2 weeks after seeding. Histidine, proline, valine, alanine, and glycine were the main amino acid residues identified during the 4 weeks of culture.
Root exudation is an important process determining plant interactions with the soil environment. Many studies have linked this process to soil nutrient mobilization. Yet, it remains unresolved how exudation is controlled and how exactly and under what circumstances plants benefit from exudation. The majority of root exudates including primary metabolites sugars, amino acids, and organic acids are believed to be passively lost from the root and used by rhizosphere-dwelling microbes. In this review, we synthetize recent advances in ecology and plant biology to explain and propose mechanisms by which root exudation of primary metabolites is controlled, and what role their exudation plays in plant nutrient acquisition strategies. Specifically, we propose a novel conceptual framework for root exudates.
play in contributing to these beneﬁcial multipartite interactions. Impacts of root exudates on soil microbial communities. A large body of literature.
Rhizosphere interactions: root exudates, microbes, and microbial communities
In this study, the root exudates of wetland plants, Pistia stratiotes , black algae , and Cyperus alternifolius , exposed to six phosphorus concentration gradients 0, 0. The experimental seedlings were cultivated in Hoagland solutions, which were then extracted, decompressed, and concentrated with CH 2 Cl 2 ; subsequently, a gas chromatography-mass spectrometry GC-MS analysis was performed to study the root exudates effects under different phosphorus concentrations. Results showed the existence of several organic compounds, such as alkanes, esters, alcohols, amines, benzene, and acids phthalic acid, cycloheptasiloxane, benzoic acid, and cyclopentasiloxane in the root exudates of the wetland plants. The relative contents of phthalate, benzene dicarboxylic acid, and cyclohexasiloxane in the root exudates first increased, and then decreased, with the change in phosphorus concentration.
Plant Nutrition pp Cite as. The complex ecosystem of the rhizosphere is characterised by conditions quite different from bulk soil. One important reason is the release of organic substances from the roots into the rhizosphere. These exudates have influences on P mobilisation both in a direct and indirect way with the help of microbes, too.
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