Rhizosphere Microbiome Flashcards
What does soil support?
-plant structural support
-plant source of water and nutrients
-growth of soil biota (a variety of organisms)
What are the 5 most important functions mediated by the soil biota?
Soil microbes enhance soil fertility by:
1) the formation and turnover of soil organic matter
2) nutrient cycling
3) disease transmission and prevention
4) pollutant degradation
5) improvement of soil structure
Define Plant-microbe interactions:
The relationships between plants and
microorganisms, can be either:
-beneficial (both partners benefit)
-detrimental (plant diseases by pathogens)
-neutral (microbs that do not affect plant)
These interactions are crucial for plant growth, health, and ecosystem functioning.
What is the phyllosphere
The above ground surface of plant parts:
-leaves
-stems
-fruit…
What is the endoshphere?
Inside plant tissures
-roots
-stems
-leaves
Where do endophytic microbes live?
In the endosphere
What is the Rhizosphere?
The soil region immediately surrounding
plant roots,
where roots secrete nutrients that attract
and support a diverse microbial community.
Exhanges between root and soil
-water
-inorganic compounds
-organic compounds
What are the factors affecting the microbial communities and plant-microbe interactions
- Environmental Factors
-Light
-Temperature
-Radiation
-Precipitation - Anthropogenic activity
-Pollution
Agricultural practices
-Crop choice
-Fertilizers
-Pesticides - Plant Factors
-Genotype
-Secondary metabolites
-Immune system
-Developmental stage
-Plant to plant interactions
-Plant part
-Root exudates
-Root morphology - Edaphic Factors
-Nutrients
-Soil pH
-Moisture content
-Microbe interactions
What are the 6 macronutrients and what is a broad overview of what they do for the plant?
(N, K, Ca, P, Mg, S)
o structural components of proteins, cell walls, membranes, nucleotides,
chlorophyll
o important roles in energy and water maintenance
What are the 8 micronutrients and they play an important role as funtional groups in ____?
Fe, Cl, Mn, B, Zn, Cu, Mo, Ni
important roles as functional groups in enzymes
What does the beneficial element Si do for plants?
Si alleviates the toxic effects caused by abiotic stresses (e.g., salt stress,
drought, heavy metals..)
What are the two most prominant forms of inorganic nitrogen?
What can V. vinifera uptake?
What factors influence their efficiency in utilizing it?
Nitrate (NO₃⁻) and ammonium (NH₄⁺)
V. Vinifera can uptake both, from the root to the shoot via the xylem in the form of nitrate, dissolved ammonia, and amino acids
Factos:
-soil conditions
-vine physiology
-environmental factors
What are the negative effects of nitrogen fertilization on the soil and environment
- Soil Impacts
-nutrient imbalance (deficiencies in K and Mg)
-soil acidification (ammonial lowers pH, reducing microbes and nutrient availability)
-loss of SOM (accelerated decomposition) - Environmental Impacts
-groundwater contamination (NO3- leaches)
-runoff into bodies of water (leads to algal blooms)
-greenhouse gas emmissions (nitrous oxide)
-atmospheric polution (NH3) - Long-term Sustainability Concerns
-dependency (no incentive for sustainable)
-soil biodiveristy loss (loss of beneficial microbes)
-unsustainable production methos (Heber-Borsch method uses high energy/fossil fuels)
Explain the phosphorus paradox and a potential way to manage it:
P Paradox:
-P essential for plant growth
-often unavailable despite being abundant in soil
-it strongly binds to soil particles = insoluble and plants cant uptake it (highly dependant on soil pH)
-it is a finite resource, from non-renewable rock
Purposed management:
-use soil microbes to solubilize P, making it available for plants
-reducing dependance on conventional P
What could be the results to the plant by engineering the rhizosphere? Also, by the mycorrhizal connection…
-increased plant resistance against biotic stresses, reducing phytochemical input
-increased plant resistance to abiotic stresses (drought, salinity, metals, mineral nutrient depletion)
-improvement of soil structure and stability
-promotion of plant growth
-bioregulation of plant development and increase in plant quality for human health
-reduction in fertilizer requirement
-increase plant/soil adherance
Microbes with plant-beneficial activity have mainly the following characteristics:
- Capability to perform Nitrogen fixation (atmospheric N2 to Ammonia)
- Capability to solubilize P from soil
- Capability to promote plant growth
- improve plant nutrition
- Biocontrol against plant pathogens
- binding and transporting iron
- activation of plant defences
- stimulation of plant growth
Explain biological nitrogen fixtation (BNF) is and what microbe/enzyme do it:
a biochemical process in which atmospheric
N2 is converted into
ammonia by
bacteria (diazotrophs)
possessing the
nitrogenase enzyme
What are the advantages and disadvantages of intercropping
Main intercropping advantages
Natural sourcing of nitrogen
Increased biodiversity
Less soil erosion
Space maximization
Yield advantage
Weed suppression
Decrease herbicide use
Main intercropping disadvantage
Competition between crops:
* water, nutrients
* not suitable in south
Europe vineyards
Planning for the growing
season needed
Potential for higher labor
costs depending on the
intercropping method chosen
P-solubilizing microbes effected plant growth how?
-promoted growth (shoot and roots)
-imporved quality of fruit
-increased nutrient content of soil
-affected bacterial community
What are the mechanisms by which Trichoderma spp. control soil-borne diseases
direct suppression of pathogens
- production of antibiotics
- production of pathogen cell walls degrading enzymes (chitinases)
- protective colonization of the root surface
- competition for nutrients or space
indirectly by strengthening the plant
- Inducing plant resistance
- tolerance to stress through enhanced root and plant development
- improving plants iron uptake
What were the beneficial activities of trichoderma on grapevine fitness
-increased pathogen control (powdery mildew)
-increased total polyphenols
-increase fruit quality
-increase in yield
Define Rhizosphere
The potrion of the soil influenced by the roots
What are Rhizobia and what do they do?
- Rizobia are Gram negative soil bacteria able to “nodulate” legume plant roots
- Heterotrophic (cannot produce food)
- In the nodules, they convert (“fix“) molecular nitrogen into ammonia NH3
- They are obligate aerobes (require oxygen for survival)
Explain the rhizobia root infection process
- Plant roots emit flavonoids to compatible rhizobia
2.Rizobia secrete Nod factors that bind to root hairs
- Binding allows entry for Ca2+: causeing root hair to swell and curl around rhizobia
- Rhizobia inject nodulin proteins and penetrate into root cortex
- Nodulins cause cortex cells to divide, creating nodules.
- Rhizobia invade nodule cells inducing further development
- Rhizobia divide and then transform into bacteroids
- Nodules become pink inside as O2- leghemoglobin is produced
- Nodules develop vascular tisse
- Vascular tissue transports nitrogen to shoot and organic carbon from shoot to nodule bacteroids
