Microbial Health of the Rhizosphere
Works Cited Missing
The importance of the interactions between microorganisms, plants and the rhizosphere was realized as early as 1904 by Soil Bacteriologist and Professor of Agronomy at the Technical College of Munich, Lorenz Hiltner. “The term rhizosphere was introduced by Hiltner in 1904.” (Gobran, 2001) Hiltner “emphasized the critical role of microbial activities in the ‘rhizosphere’ in the nutrition and general health of plants.” (Curl, 1986) The term rhizosphere was used to “describe specifically the interaction between bacteria and legume roots.” (Lynch, 1990)
Today there is debate among microbiologists and plant scientists regarding the definition of rhizosphere (Curl, 1986). “Rhizo” is derived from the Greek word “rhiza,” meaing “root”. “Sphere” is “one’s field of action, influence, or existence: one’s natural surroundings.” (Lynch, 1990 “Rhizosphere is the zone where root activity significantly influences biological properties.” (Manthey, 1994)
There are three main areas of research that are done on the rhizosphere. The first one is the “influence of roots on microorganisms.” The second is “influence of microorganisms on plant growth,” and the third is “rhizosphere influence on soil-borne pathogens and plant disease.” (Curl, 1986)
When Hiltner first talked about the rhizosphere in 1904, he stated, “The nutrition of plant in general certainly depends upon the composition of the soil flora in the rhizosphere…If plants have the tendency to attract useful bacteria by their root excretions, it would not be surprising if they would also attract uninvited guests which, like the useful organisms, adapt to specific root excretions.”
This speech identified two of the main topics of rhizosphere research: “(1) the relation of the rhizosphere to plant nutrition, growth, and development, and (2) the influence of rhizosphere phenomena on pathogens and pathogenesis.” (Curl, 1986) It was realized as early as 1904 that rhizosphere microorganisms can cause disease or transmit viruses as well as benefit the plant.
There are microorganisms in the bulk soil as well as in the rhizosphere. The microorganisms in the soil include bacteria, fungi, protists, actinomycetes, and nematodes. These microorganisms are not distributed uniformly around the soil; they are congregated around nutrient sources. A nutrient source for these microorganisms is organic matter. (Curl, 1986)
In the rhizosphere there are different amounts and types of microorganisms than there are in the bulk soil due to different substrate, or “the surface on which an organism grows or is attached.” Other factors that vary from rhizosphere to bulk soil are the acidity, moisture, nutrients, electrical conductivity, and redox potential (Lynch, 1990).
within the soil. In this experiment, the liberation of ammonia is being employed as an indicator. Other components being utilized play a vital role in controlling the conditions of the experiment, as the THAM buffer, and the limitation of microbial activity, through toluene. The control experiment is crucial as it eliminates the addition of ammonia content being released by other sources within the soil into the final reading, providing accurate data.
As a result of these factors, the flora has adapted to these conditions in a variety of ways including their shape, leaf type, root system, and color. One of the most prominent adapt...
(ii) Motility and chemotaxis. In addition to their role in the attachment of microorganisms to plant roots, functional flagella are important for bacterial motility. The crucial role of motility for successful rhizosphere colonization is somewhat controversial because some studies have indicated that motility of Pseudomonas is not required for root colonization in wheat and soybean (Howie et al. 1987). However, flagella were shown to be essential for colonization of potato roots (de Weger et al. 1987). Studies confirming the role of motility in the colonization process were performed in the absence of percolating water, and it was assumed that motile or non-motile introduced bacterial strains were transported by the growing roots. However, under more natural conditions the presence of percolating water will affect the dispersal of bacterial strains regardless of their ability to swim.
Schumann, Gail L., and Cleora J. D'Arcy. Hungry Planet: Stories of Plant Diseases. St. Paul: American Phytopathological Society, 2012. Print.
Mycorrhizae are a type of fungus that helps the plant’s productivity by absorbing more nutrients, help it grow, and improve on the root system (Fan et al 2011). It also helps the plant take up nutrients, like nitrogen and phosphorus, help against the effects of water scarcity, and increase the health of the plant by protecting it from diseases and insects (Saia et al 2014). The mycorrh...
2. (2 pts) Contrast the potential contributions of Azotobacter versus Rhizobia/Bradyzhizobia to the nitrogen budget in soils. Discuss why they are so different.
...nges in soil structure and soil biota of nutrient-poor grassland. Global Change Biology 9: 585-600.
Microbes are everywhere in the biosphere, and their presence invariably affects the environment in which they grow. The effects
...e involved in the plants carbohydrate metabolism. This response causes the plant’s cell walls to be rearranged and strengthened. THis would increase the plants resistance to infection and the uptake of harmful chemicals.
Plants like many eukaryotic composed organisms have the ability to detect and protect themselves against microorganisms known as pathogens. Plant fossils have recorded that land plant’s existence was established 480 million years ago, but molecularly, plant evolution began 700 million years ago. Molecular interaction with microbes and other organisms gave the shape and structure of plants, giving us an idea that microbes also evolve according to its host. Plants lack mobility depriving themselves from a somatic secondary immune response like many mammals giving pathogens the ability to easily attack. Pathogenic microbes can access plants by penetrating through the leaves, entering through plant wounds, or by using the stomata a natural pore on plants that opens and closes for gas exchange. To detect and stop from extensive damage from microbes, plants developed an immune system through its structure, chemicals, and defense proteins.
Cook, R.J. “Influence of Water Potential of Soils and Plants on Root Disease”. Annual Reviews: A
The effect of soil salinity in plant growth is part of botany, the study of plants.
Soil is the most important non-renewable resource on any farm. Healthy soil is key to a good
However, it certainly indicates that the microorganisms studied are genomes or virtual taxa, using metagenomics method. Studies of rhizosphere microbiome present a holistic view of diversity and interaction across the habitat. Consistent with the terminology used for microorganisms colonizing the human body the collective communities of plant-associated microorganisms are referred to as the plant microbiome or as the plants’ other genome (Qin et al., 2010). In this context, plants are viewed as ‘superorganisms’ which is partly dependent on their microbiome for specific functions and traits. This includes all plant associated microbe habitats such as rhizosphere, spermosphere (seed surface), phyllosphere (leaf surface), and the stem microbiome. Recent application of microbial metagenomics, metatranscriptomics, and metabolomics to plants and their surroundings confirm a key role of mycorrhizal fungi, rhizosphere bacteria and fungi in determining the make-up of rhizosphere microbial community and suggest a world of hitherto undiscovered interactions in the rhizosphere (Dickie et al. 2015). This knowledge is leading to a paradigm-shifting view that plants should be considered as a meta-organism or holobionts instead of isolated
pH is the measure of how acidic or basic a substance is. Soil acidity or alkalinity is important because it influences how easily plants can take up nutrients from the soil. pH stands for “potenz Hydrogen” where “potenz” meaning “the potential to be”. The degree of activity of hydrogen ions in solution determines the acidity or alkalinity of the solution. Acidic solutions have a high concentration of hydrogen ions; alkaline solutions have a low concentration.