Week15 L3: Plant-Microbe Interactions - NITROGEN Flashcards
Why are minerals to important?
Make up enzymes, biological membranes, amino acids, protein, enzymes and co-enzymes.
Part of the biological processes in the plant to complete its lifestyle.
What is the difference between macronutrients and micronutrients? (2 divisions of nutrients)
macronutrients need a higher conc of, more likely to be deficient due to their larger amount.
What does photodeficiecy harm in plants?
plants will not be able to photosynthesise
How can farmers see what their pant is deficient in?
leaf discolouring
What is the major limiting nutrient in crop production?
nitrogen
What form of N can plants uptake?
N2 to nitrate and ammonium
What is the conversion of di-nitrogen to a form plants can uptake?
nitrogen fixation
What is the process of making synthetic nitrogen fertilisers?
industrial fixation
How much of the population rely on industrial fixation of nitrogen? (synthetic nitrogen)
50%
What are the issues with nitrogen fertilisation?
cost
major pollutants (nitrous oxide)
algal bloom
What are the problems when synthetic fertiliser is added to crops? and example of where?
algal bloom
leek into water and algae will grow exponentially to cover the water (pond) green, contamination.
run-off into gulf of Mexico.
Overuse can harm the environment. fertilizer application produced greenhouse gases e.g. nitrous oxide and pollutes waterways.
How many molecules does biological nitrogen fixation process? Biological nitrogen fixation.
per 1 molecule of atmospheric nitrogen it requires 16ATP to fix… very costly
What is the enzyme involved in atmospheric nitrogen conversion?
nitrogenase
What is BNF?
biological nitrogen fixation
What is plant symbiosis?
describing any relationship or interaction between two dissimilar organisms.
What are the rhizobia?
soil bacteria which colonise the root of plants. in symbiosis with legumes
Can legumes recognise any symbionts?
NO, they are very specific
Can legumes recognise any symbionts?
NO, they are very specific
Almost a 1:1 RATIO
Specific legume hosts recognise specific symbionts through their node factors
What are the 2 types of nodules involved in nitrogen fixation?
determinate andindeterminate
What organ does a plant need to carry for biological nitrogen fixation?
Node
What is Nitrogen fixation?
the chemical processes by which atmospheric nitrogen is assimilated into organic compounds, especially by certain microorganisms as part of the nitrogen cycle.
Can the function of a given plant nutrient be be replaced by another?
NO
What are the non-mineral nutrients?
carbon, hydrogen, oxygen
What does lack of phosphate look like in a plant?
purple discolouration
discoloured areas wont photosynthesise
What an example of a greenhouse gas which fertilizer application produces?
nitrous oxide
What is an alternative to industrial nitrogen fixation?
biological fixation
What is biological fixation?
Several soil Archaea
and Bacteria can fix
di-nitrogen as ‘free-living’ organisms or in symbiosis with plants and fungi
Why would organisms carry out biological nitrogen fixation?
Something or someone providing them with a source of energy. Otherwise its just a metabolic burden.
They would likely be outcompeted by competitors.
What is plant-nitrogen fixing microbes symbiosis?
mutually beneficial arrangement
How is the plant-nitrogen fixing microbes mutually beneficial? Called Root nodule symbiosis
Trading reduced molecules
The plant provides organic carbon derived from
photosynthesis, and the bacteria provide fixed nitrogen.
Most rhizobia cannot fix nitrogen except in nodules
What is the specific plant-microbe interaction?
rhizobia and legumes
What are the bacteria which fix nitrogen?
rhizobia
What source of nutrients do we get from legumes?
major source of protein
What are the 4 steps in the formation of the root nodule?
Step1
- Communication: flavonoid (plant) attracts a specific rhizobia. The nod factors (rhizobia) recognise this signal and identify them as appropriate symbionts.
When the rhizobia binds to the specific receptors of the legume, it decides of this is the compatible bacteria.
The nodulation process starts.
Specific legume hosts recognise specific symbionts through their node factors
What are the 4 steps in the formation of the root nodule?
Step2
Nod factor perception induces root hair curling.
The root hairs trap the rhizobia present in soil.
Leads to the formation of the process relating to the nod.
What are the 4 steps in the formation of the root nodule?
Step3
Infection thread growth
Rhizobia must get from the root surface to the inner root tissue where they will populate cells in the incipient nodule. To do this, they grow and divide inside a tubule called an infection thread (the tubule is plant derived and “filled” with bacteria).
What are the 4 steps in the formation of the root nodule?
Step4
Nodule growth development
- Legume nodules form from cell divisions in the root cortex
- Rhizobia transform from rod-shaped bacteria into Y-shaped bacteroids
- Within the nodule, bacteroids are surrounded by a specialised membrane called symbiosome
What are the2 fates of the nodule?
Determinate and indeterminate
What are determinate nodules?
more homogeneous and
lose the apical meristem
What are indeterminate nodules?
They keep growing retain a nodule meristem that is the site of cell proliferation, and have zones of different activities
