lec 13

Question 1

where is the rhizoplane, rhizosphere, and bulk soil located?

Answer 1

rhizoplane: immediately on the surface

bulk soil: the soil not directly affected by the root

rhizosphere: the soil adjacent to the root that is affected by it

Question 2

how does the haber bosch process work?

Answer 2

takes N from the air and combines it w H, mixes it up in a hot + pressurized environ, and makes cooled liquid ammonia

Question 3

N is super abundant in the atmosphere. why cant we use it more?

Answer 3

N has triple bonds which make if difficult to break down. the limit on nitrogenase is that it requires anoxic conditions to work

Question 4

what are the requirements for N fixers to fix N? how do they attain this?

Answer 4

require anaerobic environments
- bacteroid membrane: plant membrane around each bacteria creates an oxygen barrier
- leghaemoglobin: protein that maintains a low O2 environ in the rhizobia by delivering just enough oxygen to bacteria to facilitate respiration

Question 5

what is nodulation, and why do plants do it? what is the process?

Answer 5

nodulation is the creation of symbiotic rhizobia
when seeds are growing, they excrete chemicals (flavonoids) attracting in rhizobia which in turn release chemicals that cause root hairs to curl + form nodule

rhizobia pen root hair membrane, entering the cortex (below epidermis)

regulated by Nod genes in rhizobium

Question 6

what are the top three highest N fixers

Answer 6

faba beans are the highest N fixers, w groundnut and soybean following closely behind

Question 7

what are mycorrhizae? what are the benefits of taking them up?

Answer 7

fungi that live in plant roots and undergo symbiosis with plants

benefits incl
1. protecting the roots
2. functionally increasing root area
3. strengthening the soil (glomalim glycoprotein binds soil)