Lecture 6 - N and Phosphorous Flashcards
What is N needed for in plants?
N is needed to make AA, proteins and other cellular constituents.
What does N deficiency cause?
Stunted growth and chlorotic leaves from chlorophyll damage.
What proportion of air is N?
78% of air is N.
Why is making biologically available N difficult?
Because N2 is a triple bond, pretty hard to break.
What’s the Haber process reaction?
N2 + 3H2 -> 2NH3
What temperature and pressure is required in the Haber Process.
Temperatures between 300-600c and high pressures of 20-80MPa.
Unfortunately however, this has a relatively low yield.
What proportion of global energy is used for the Haber process?
A surprisingly high 2%.
What % of Ammonia is used to make fertiliser?
85%
How many tons of oil make 1 tonne of fertiliser?
2 tons per 1 ton of fertiliser.
Why is symbiosis useful for plants in terms of N usage?
Microorganisms help breakdown N2, pretty beneficial to plants and the microorganisms get some carbohydrates as a reward.
Why is reduction of nitrate to ammonia important?
Because it also provides N, typically found in the soil.
What amount of Mt per annum do nitrate reduction and N2 fixation give per year.
20k Mt per year for nitrate reduction.
200K Mt per year for N2 fixation.
What’s the three main issues with the haber reaction?
1 It’s super sensitive to oxygen
What do rhizobia bacteria do?
Rhizobia form an infection thread, which means they form an invagination of theplasma membrane in root hairs. A tube is formed and they can enter.
In legumes for every 100C fixed in leaves, how much goes to the nodules?
1/3 of C goes to the nodules.
Of this third, 5C grown and maintance. 12C production of NADH/ATP to fix N and 15C for assimilation of NH3.
Name two other ways plants can get C.
Parasitism.
Carnivorousness.
Is NH3 toxic to plants?
Yes, increased sensitivity to low temperature and necrosis.
How much micrograms m3 of ammonia can a plant tolerate per year, day and hour.
75m3 per year on average.
However 600 per 24 hours and 10k per hour is the tolerance limits.
What is the glutamate synthase cycle?
A cycle that converts ammonia to glutamate.
What is glutamate the raw material for?
Production of amino acids and chlorophyll.
What is P needed for?
Growth, photosynthetic capacity/rate, phospholipids etc.
What % of Phorphorous is used as fertiliser
98%
How do we get phosphate back?
Takes millions of years :(
How much Mt of phosphate ends up in the oceans per year and how much of it is used and wasted.
- 5Mt of phosphate ends up in the ocean every year.
2. 5Gt used by oceanic life, 19Mt completely wasted.
What % of P is at Morroco?
51%, sadly P use is increasing too.
How can these phosphate issues be dealt with?
Phosphate may be applied more efficiently.
80-90% of P applied as fertiliser bound to soil and biologically unavailable :(
Fertiliser directly delivers as little as 1-5% of plant P demand.
Also can try help recycle phosphate.
Give two biological adaptations for increasing phosphate uptake.
1 Cluster roots - really densely packed proteoid roots which massively increase root surface area.
What type of acid to cluster roots also produce?
Citric acid.
What does citric action cause in reactions?
Citric acid swaps the carbohydrate and citric acid for the phosphate, releasing the phosphate into the soil which then can be taken up by the roots.
What alternatives to phosphate may some plants show?
Galactolpiids and sulpholipid membranes may be used instead.
Also reduced protein production
How may a plant produce lower protein?
Preventing young leaves photosynthesising.
Having few ribosomes, so produce proteins more slowly.
