Rhizosphere and diversity Flashcards
What is the rhizosphere?
the Rhizosphere is the soil that is at the interface of plant roots and is influenced by root secretions and associations with microorganisms.
It has high carbon, stability and biological activity
How can we split the rhizosphere into sections (and describe them)
- Endorhizosphere: includes the endodermis and parts of the root cortex. Here microbes colonise inter-cellular and cellular space
- Rhizoplane: soil directly adjacent to the root - including epidermis and mucilage
- ectorhizosphere: soil extending out to bulk soil
Describe the gradient of biological activity in the soil
biological activity decreases as you move away from the endorhizosphere
How is fixated carbon allocated to the roots?
25-50% fixated carbon is allocated to the root
- of this, 25-50% is deposited as rhizodeposits
What is a rhizodeposit?
A rhizodeposit is anything that the root produces and deposits into the rhizosphere, including: sloughed-off root cells, tissue and metabolites
How can we divide rhizodeposits?
into cells and metabolites.
Cells include: sloughed-off cells, senescent tissue and epidermic cells, border cells and soluble lysates
metabolites include: root exudates, mucilage, volatile compounds
what is special about border cells?
They remain metabolically active and can produce anti-biotics, enzymes and sugars that regulate growth of bacteria, fungi and disease in the rhizosphere, protecting the plant root
Tell me about root exudates
root exudates come from the root meristem and attract/promote bacteria that colonise the rhizosphere and produce biofilms, as well as promoting mineral lability
brief me on phosphorus availability and root exudates involvement
Phosphorus is bioavailable as dihydrogen phosphate and hydrogen phosphate. soil climate conditions dictate the lability of phosphate and other minerals, and phosphate is often bound to Al, Fe, Ca, etc (it’s highly insoluble).
Organic acids produced by exudates have affinity for soil minerals, freeing up and making P labile and bioavailable. Microbes do this too through the production of acid phosphatase
Tell me about metals and exudates
similar to phosphate, rood exudates chelate metals (like Fe and Mn). Chelate structures are diffuse into roots and plasma membrane transporters shuttle them into cells
Tell me 4 types of root
-Primary root
-lateral root
-seminal root
-adventitious root (non-root tissue)
tell me about roots in cereal crops
roots in cereal crops are more complex because they have more layers of cortical cells
How do roots adapt to low N and P
Less vertical growth and more lateral growth through lateral roots
