Already have an account? Get multiple benefits of using own account!
Login in your account..!
Remember me
Don't have an account? Create your account in less than a minutes,
Forgot password? how can I recover my password now!
Enter right registered email to receive password!
Nitrogen Control of Nitrogen Assimilation
N2-fixer like Klebsiella pneumoniae and Nostoc can grow with N2, NO-3 or NH+4 as nitrogen source. You would like to know how these organisms manage to assimilate one of the three forms of N2 when given all the three simultaneously. It is known that NH+4 is preferred over NO-3 or N2 as nitrogen source. Now the question is how this preference is realised by such N2-fixers? Ammonia can readily enter the cells by diffusion and the cells assimilate ammonia thus available into glutamine and glutamate. Under such conditions the ratio of glutamine to α-ketoglutarate rises which is a signal for sufficient nitrogen and causes repression of both NO-3 assimilation and N2-fixation system. This is analogous to ATP/ADP ratio which signals the energy-state of a cell.
A high ATP/ADP ratio indicates that the cell has sufficient energy to perform its metabolic functions. That is why legumes grown in the medium containing NH+4 do not form nodules with Rhizobium. In this connection it is important to point out that recognition mechanics as explained earlier of Rhizobium-legume symbiosis is not seen in root hairs of legume supplied with NH+4. Similarly, when a N2-fixer is exposed to NO-3 and N2 it preferentially assimilates NO-3 and such NO-3 assimilating organisms do not produce N2-fixing apparatus. The mechanism of NO, inhibition of N2-fixation is the same as that described for NO-3 inhibition of N2-fixation. The mechanism of ammonium repression of NO-3 assimilation occurs through the same mechanism as ammonium repression of N2-fixation. This explains why N2-fixation, nodule formation and heterocyst formation occur under conditions of limited nitrogen and not under conditions when nitrogen is available to the plant.
Q. What is a mixed gland? Why the pancreas is considered a mixed gland? Mixed gland is a gland that produces exocrine and endocrine secretions. The pancreas is an example of
what is the classification of protozoa
Eye complications are very common in patients with diabetes. In fact, diabetes related eye diseases may not produce symptoms for a very long time and hence, it remains undetected t
What is the Endoplasmic Reticulum The cytoplasm of most eukaryotic cells contains a very complex network of internal membranes, called the endoplasmic reticulum, which forms ch
What are the types of evaluation of lateral earth forces acting on retaining structures? This section seeks to introduce you to the evaluation of lateral earth forces acting on
Most proteins made by ribosomes on the RER (rough endoplasmic reticulum) are glycoproteins, which is they hold short chains of carbohydrates (oligosaccharides) covalently related t
Q. What are the three major signs of diabetes? The three major signs of diabetes mellitus are known as the diabetic triad- polydipsia, polyuria and polyphagia. Polyuria is t
Explain in detail about the optic nerve The optic nerve contains more than one million axons that initiate in the ganglion cell layer of the retina. This structure originatcs a
HIS T O R Y - Protoplasm was first seen by Corti, 1772 F . Dujardin called it "Sarcode" & observed it in animal cell Term "Protoplasm" was given by J.E. Pu
Sporotrichosis Sporotrichosis is subacute or chronic infectious disease caused by a dimorphic fungus, Sporothrix schenkii which occurs commonly in soil, wood and vegetation. T
Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!
whatsapp: +1-415-670-9521
Phone: +1-415-670-9521
Email: [email protected]
All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd