Microbial Health of the Rhizosphere :: Biology Bacteria Science Essays Papers

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. â€Å"The term rhizosphere was introduced by Hiltner in 1904.† (Gobran, 2001) Hiltner â€Å"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 â€Å"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). â€Å"Rhizo† is derived from the Greek word â€Å"rhiza,† meaing â€Å"root†. â€Å"Sphere† is â€Å"one’s field of action, influence, or existence: one’s natural surroundings.† (Lynch, 1990 â€Å"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 â€Å"influence of roots on microorganisms.† The second is â€Å"influence of microorganisms on plant growth,† and the third is â€Å"rhizosphere influence on soil-borne pathogens and plant disease.† (Curl, 1986) When Hiltner first talked about the rhizosphere in 1904, he stated, â€Å"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: â€Å"(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 â€Å"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).