Week 3 Flashcards
What are the 6 macronutrients?
Nitrogen
Phosphorus
Potassium
Sulphur
Magnesium
Calcium
What are John Woodward’s conclusions?
Woodward concluded that mineral matter nourishes plants.
What were the impact of John Woodward conclusions?
These conclusions layed the foundation for the study of plant mineral nutition
What experiement did John Woodward do?
He compared plant growth in water different amounts of ‘mineral matter’ to test the assumption that water is a plant’s sole requirement.
What were the results of John Woodward’s experiments?
Spring water - plant weight increased by 55%
Rain water - plant weight increased by 62%
Thames River Water - plant weight increased by 93%
What is the “law of minimum”?
Growth of the plant will always be determined by the limited nutrient
When did Lawes and Gilbery start investigating plant nutrition?
They started in 1843 at Rothamsted, which is still researching today
Where does nutrient assimilation take place?
They take place across the surface of the plant or through the root system of vascular plants
What are the 8 micronutrients?
Iron
Nickel
Manganese
Copper
Molybdenum
Boron
Chlorine
Zinc
Which ions of nitrogen, phosphorus, sulphur, molybdenum and boron aren’t assimilated as compounds?
Nitrogen - NO3 -, NH4 +
Phosphorus - HPO4 2- , H2PO4
Sulfur - SO4 2-
Molybdenum - MoO4 2+
Boron - H3BO3
What is requred for the transportation of charged ion?
They require proteins to cross membranes
How do roots increase effciency?
They increase the surface area for absorption
What are the similarities between microvilli and roots?
They are structurally similar but inverse as they need to absorb nutrients in rather than absorb nutrients out into the blood
What are the adaptations to enhance nutrient capture?
Biochemical response - root exudates
Fungal symbiotic partners - mycorrhizae
Developmental responses - cluster roots
Prokaryotic symbiotic partners - Biological nitrogen fixation
How does soil pH change around the world?
Deserts and other dry areas are mildly alkaline comapred to forests which are strongly acidic
How does soil pH impact nutirents?
Different pHs impact the percentage of uptake of soil nutirents with each nutirent having a more optimum pH
What things affect soil fertility?
Erosion, rainfall patterns, cultural practices, soil biodiversity, soil pH and atmospheric gases
What are the main 3 elements in fertilizers?
Nitrogen
Phosphorus
Potassium
What are the two types of fertilizers?
Natural - waste products
Artifical - refinded blends of nutirent salts
Are resources constant around the planet?
No, different regions have different amounts of resources. So areas like USA have greater supply of K2O than demand but has lower N than demand compared to Russia/Eastern Europe which has greater supply of both K20 and N than demand
How much is the fertilizer trade worth?
$231 billion dollars in 2021
What factors impact the amount of fertilizer used?
Species of plant
Soil characteristics
Cultivation practices
Abiotic and biotic factors
Financial considerations
Interactions between nutrients
What are the problems of fertilizers?
Nitrogen fixation is energy demanding
Phosphate and potash mining is destructive
Huamn and animal waste can spread disease
Transport requires energy
Nutrient runoff pollutes waterways and can lead to eutrophication
Nitrous oxide derived from fertilizer is a major greenhouse gas
Where are minerals naturally come from?
Rock weathering
Decaying matter
Organic matter
Inorganic matter
How much does food production increase inbetween 1960 and 2000?
1.8x10^9 to 3.5x10^9
How much does nitrogen fertilizer use increase inbetween 1960 and 2000?
10x10^12g (10 Tg) to 88x10^12 (88 Tg)
How abundant is nitrogen in plants and the atmosphere?
Most abundant elements in atmosphere
4th most abundant element in a plant after C, H and O
Why is nitrogen is important?
In amino acids
Nucleic acids
Chlorophyl
Other small molecules
What element is often the limiting nutrient for plants?
The limiting nutrient for plant growth is nitrogen
What is the difference between nitrous oxide and nitric oxide?
Nitrous oxide - N2O
Nitric Oxide - NO
What is the difference between nitrous acid and nitric acid?
Nitrous acid - HNO2
Nitric acid - HNO3
What do nitrifying bacteria do?
Convert ammonium to Nitrogen dioxide to nitrate
This releases energy
What do plants to produce organic nitrogen?
Using energy and the enzyme nitrate reductase
NO3- to NO2- to NH4+ to R-NH3
Do plants prefer NH4+ vs NO3-?
Plant preferences for NH4+ vs NO3- vary by species, other metabolic processes, temperature, water, soil pH
What are HATS?
High affinity transporters - can transport either ammonium, nitrate, amino acids and urea depending on the transporter in high concerntrations
What are LATS?
Low affinity transporters - can transport either ammonium, nitrate, amino acids and urea depending on the transporter in low concerntrations
What happens to nitrate within the plant?
Other Channels contribute to nitrate transport within and between cells
Name Ammonium channels?
AMT 1.1 = HATS
Name nitrate uptake channel?
NAR 2.1 = HATS
NRT 1.2 = LATS
Name an amino acid uptake channel?
AAP1
Name an urea uptake channel?
DUR 3 - HATS
TIPS - Passive
What happens to uptaken NH4+?
It gets assimilated into organic compounds like glutamine
What happens to uptaken R-NH3?
It gets assimilated into NH4+?
What is glutamine used for?
It is converted into all other nitrogen containing compounds
What is remobilization?
Amino acid recycling and photorespiration which produces NH4+
What happens to recycled and uptaken NH4+?
It is converted into glutamine using glutamate by glutamine synthetase (GS)
What happns to the glutamine?
Some is incorporation into nitrogen-containg compounds
Some of the nitrogen is split and bonds with 2-oxoglutarate to glutamate using glutarate aminotransferase (GOGAT) which then bonds wirh NH4+
Can nitrogen go through GS many times?
Yes, they can go through GS many times many times as amino acids are recycled during growth and senescence and relewased due to photorespiration
What does a plant do in response to nitrogen deficit?
Activation of some NO3- and NH4+ transporters
Preferential growth of root relative to shoot
What are metabolic adaptations to low nitrogen?
Decreased accumulation of N-rich chlorophyll
Increased accumulation N-free anthocyanins
Smaller pools of N-containing compounds (amino acids)
Larger pools of N-free compounds (starches, organic acids)
Accelerated senescence and nitrogen remobilization
What happens to roots when nitrogen is abundant?
Plants allocate less biomass to their roots
What happens when nitrogen distrubution is patchy?
Roots distrubution proliferate in nutrient rich patches
In an experiment where half roots are in low NO3- conditions the other in high how did the roots grow?
They grow heavily in the nutrient rich areas but only partially in nutrient poor areas
What is co-cropping?
Growing crops with legumes to enrich soil N content
What is grop rotation?
Rotating crop in order to maximise growth rate and replace some lost minerals
How can you determine n content?
By determining chlorophyl content which is measured by reflected light
What is the transmission ratio of chlorophyll?
Ratio of 653nm to 931 nm
What is the Haber Bosch process?
Industrial production of ammonia
When was the Haber Bosch process invented?
1910
What are the problems of the Haber Bosch process?
Requires expensive metal catalyst
High pressure and temperature
What is the advantage of the Haber Bosch?
The industrial production of ammonia means that large amounts of fertilizer allowing farming to meet rapid population increase
What is the Rhizobia that is in a symbiotic relationship with soybeans?
Bradyrhizobium japonicum
What is the advantage of soybean production?
5-10x more protein then dairy cattle and more than 15x than meat production
They dont need to add N fertilizer
What happens to an uninoculated legume plant?
Whiter less developed leaves
Smaller leaves
What are AM fungi?
Arbuscular mycorrhizal fungi
How many plants have a symbiotic relationship with AM fungi?
80% of land plants
What do AM fungi provide plants?
Increases surface area so increased absorbtion of Phosphorus, Micro-nutrients and water
When did AM fungi, plant symbiotic relationship evolve?
Approxiamately 400 mya, land plants evolved 450 mya
When did the symbiotic relationship between Rhizobia and legumes?
65 mya
What groups are considered legumes and have evolved a relationship with Rhizobia?
Fabales, Fagales, Cucurbitales and Rosales
What is special Gunnera and Nostoc?
The only intracellular symbioses
What is the first step in the formation of plant nodulations?
Molecular dialogue between the host plant and microbial symbionts using diffusible signals
What is the structure flavonoids?
Polyaromatic secondary metabolites consisting of a 15-carbon skeleton
How are flavonoids produced?
Phenylpropanoids pathway
What are examples of flavonoids?
Flavonol, flavone, flavanone and isoflavone
What are nodulation factories?
Are chemical signals which signal to plants to start the formation of plant root nodules
What is scientific name of nodulation factors?
Lipochitooligosaccharides (LCOs)
What is the structure of the backbone of nod factors?
A chitin (saccaharide) backbone
Usually 3 to 5 Beta-1,4linked N-acetylglucosamine residues
Where is the acyl chain located?
On the non-reducing terminus
What’s important about the R groups?
They are decorations which are added to the backbone which vary between Rhizobium strains and species
What things that can be added to the R groups of nod factors?
Acetyl, methtl, sulfate and sugar moieties
What produces nod factors?
Nod factors are mediated by nod genes
What does gene D do?
Controls expression of other nod genes
What happens when flavonoids are perceived?
NodD binds to nod box found in promoters of nod genes
What does nod A,B,C do?
Codes for the Nod-facotor backbone
What does nod E and F code for?
They determine which acyl chain is added to Nod Factor backbone
What does nod H code for?
O-sulfation of Nod factor
What does nod L code for?
O-acetylation of Nod factor
What does node I J code for?
Nod factor export (ABC transporter)
What is the second stage of plant nodule formation?
Host plant signalling
What happens when nod factors bind to plants?
This activates Ca 2+ spiking machinery
What happens when Ca 2+ spiking machinery activates?
Ca 2+ spike pccurs
Where does calcium spiking occur?
Calcium spiking occurs in the nucleus
What is useful for scientists about calcium spiking?
One of the earliest measureable responses to Nod factor (within minutes)
What decodes for the calcium?
A unique calcium and calmodulin-dependant protein kinase (CCaMK)
What is the 3rd stage of plant nodulation formation?
Attachment and infection
What does Nod factors do to root hairs?
Nod factors induce root hair deformation in legumes
What do the Rhizobia do in response to deformed root hairs?
Rhizobia form a biofilm and attach to root hairs
What happens to plant lectin in acidic and basic conditions?
Acidic - localised on root hair tips
Basic - Solubilized so an alternative method of attachment is used
What is released by the bacteria to attach to root hair in basic conditions?
The extracellular rhizobial protein rhicadhesin which attaches to the rhizobial cell surface and the root hair in a calcium-dependant manner
What is the biofilm made by bacteria made from?
Cellulose
What happens to the Rhizobia when the root hair curls?
The rhizobia are entrapped with in the root hair curl
What is the name of the micro-colony entrapped with in the root hair cell?
The micro-colony within is called the shepherd’s crook
What happens to after the bacteria are trapped by root hair cell?
Hydrolysis of the plant cell wall and invagination of the plasma membrane leads to the formation of a tubular strucutre termed the infection thread
What happens to the root to form the infection thread?
Extensive cytoskeletal remodelling, inclusing reorganisation of actin filaments and microtubules
What is the final step of plant nodulation formation?
Symbiotic organ formation
What keeps the bacterial infection tightly coordinated?
The organogenesis of nodules
Plant hormones
What does Ethylene, jasmonic acid, salicylic acid and ABA do?
Negetively regulate Nod factor-induced calcium spiking, early gene expression and infection thread initiation
What does cytokinin, ABA and auxin do in the cortex and pericycke cells?
Cytokinin, ABA and auxin balance dictate where lateral roots or nodules will be initiated
What is the final function of ABA?
Coordinating the epidermal and cortical programs as it plays roles during both stages
What are the key features of inderminate nodules?
Elongated in shape
Tip-growing meristem
Initiated from inner cortical cells
Found in Medicago and Pisum
What are key features of determinate nodules?
Round in shape
transient meristem
Initiated from outer cortical cells
Found in Lotus and Glycine
What are the 4 zones of the nodules?
1 - Meristem
2 - infection
3 - Nitrogen fixation
4 - senescence
What establishes a symbiosis?
Symbiosis signalling
What are bacteroids?
Bacteria which have differentiated form of rhizobia - bacteroids ‘N2 fixing form’
What happens to the bacteria in the nodules?
They are released from infection threads as infection droplets and are engulfed by the cytoplasmic membrane to form peribacteroid
What is kept low in order to start nitrogen fixation?
O2 levels are kept low by lehaemoglobin
What can fix nitrogen?
Nitrogen fixation is exclusively a prokaryotic property
What fixes nitrogen in the bacteria?
Nitrogenase - a multi protein component enzyme
What codes for the nitrogenase enzyme?
nif genes
What is the equation for nitrogen fixing?
N2 + 16 ATP + 8 H+ + 8 e- = 2NH3 + 16ADP + 16 Pi + H2
What is the metal component used in the fixing of nitrogen?
FeMoCo
What is the speed of nitrogenase?
Nitrogenase is slow
12 electron pairs per second, only 3 molecues of N2 per second
How demanding is nitrogenase for energy?
Nitrogenase is very energy demanding
16 ATP per N2 fixed
20 grams of glucose per gram of NH3 synthesised
How sensitive is nitrogenase to oxygen?
Nitrogenase is very sensitive to oxygen
Iron protein has a half life of 30 seconds in air
What are bacteroids fed?
Carbon in the form of dicarboxylic acids (malate) and amino acids
What is made by the plants to help nitrogenase?
homocitrate
What is the function of homocitrate?
A FeMoCo cofactor
What happens to the NH4+ produced by the bacteria?
It is assimilated by the plant via glutamine synthetase
