Rhizosphere

Rhizosphere in soil

1. RHIZOSPHERE Presented by: Narpat Singh Msc . 3 rd sem

2. What is Rhizosphere ? The region of the soil in contact with the roots of a plant. It contains many microorganisms and its composition is affected by root activities. In another word, it is an environment under the influence of plant. The rhizosphere was defined by Lorents Hiltner as “the soil compartment influenced by the roots of growing plants.” “Root zone.”A very narrow zone (a few mm) around the root. Contains root exudates and microbes. Rhizosphere is a relatively stable, nutrient-rich environment.

3. The Rhizosphere is the zone surrounding the roots of plants in which complex relations exist among the plant, the soil microorganisms and the soil itself. The plant roots and the biofilm associated with them can profoundly, influence the chemistry of the soil including pH and the transformation of mineral compounds.

4. Rhizosphere can be divided into： Inner rhizosphere : the very root surface Outer rhizosphere : embracing the immediately adjacent soil

5. Rhizodeposition Release of organics form roots. 5-20% roots exucants Rhizodeposition describes that total carbon transfer form root to soil. Plants roots secrete various nutrients rich compund into the surrounding soils,this process called Rhizodeposition . Rhizodeposition can amount up to 25% of newly fixed photosynthates .

6. This nutritional enrichment around roots creats unique environment for soil microorganism including the rhizosphere (that’s volume of soil around roots influenced by roots exudation) and the rhizoplane (the immediate root epidermal surface that interfaces that rhizosphere soil. It includes releases come form secretion , exudates , lysates , mucilage and mucigel . The term rhizodeposition includes (Root exucates , mucilage , death & decay part of root). Mucilage:- Root mucilage form a gelatinous layer surrounding the root tip and is one of the few clearly visible signs of organic carbon excretion from roots. Its mainly composed of polysaccharides of 106-108 Da in size and its actively secreted by exocytosis from root cap cells. Alongside polysaccharides , its also contains proteins and some phospholipid.

7. Exudates:- exudates are defined as diffusible compound which are lost passively by the root and over which the root extract little control. The dominants organic compounds in roots reflect those compound central to cell metabolism and include free sugers , aminoacid and organic acid Lysate:- compound released of death and lysis of root cells

8. Rhizosphere effect Compared to non-rooted bulk soil , the rhizospheric soil around the plant root contains much larger population of microorganism. A stimulation that can be put on a quantitative basis by the use of the R：S ratio R：S ratio = number of microorganisms in the rhizosphere soil：number of microorganisms in the non- rhizosphere soil. R/S > 1, good stimulation R/S = 1, no stimulation R/S < 1, inhibition

9. Plant affects the rhizosphere microorganisms through the release of root exudates What is root exudate? Small molecules that are released from plant roots, which include sugars, amino acids, organic acids and amides.  These molecules influence soil nutrient availability both directly and indirectly by stimulating the activities of certain microbial and fungal components of the soil biota.

10. Organic Compound Released by Plant Root Sugars and Polysaccharides. Amino Acids. Organic Acids. Fatty Acids. Sterols. Growth factors. Enzymes. Flavonones and Nucleotides.