Symbiotic nitrogen fixers - nutrient cycles, Biology

Assignment Help:

Symbiotic Nitrogen Fixers - Nutrient Cycles

Of the symbiotic nitrogen fixing bacteria, species of Rhizobium form root nodules in legumes and are the most studied nitrogen fixers and the best understood. Species of Rhizobium are most specific to particular species of legumes. The rhizobia penetrate the root hair and once inside the root, the bacteria rapidly multiply and form swollen, irregular - shaped bodies in roots of legumes. Some non-legume w6ody plants also have root nodules and fix nitrogen symbiotically.

The organisms that cause the formation of nodule and fixation of nitrogen are actinomycetes (a kind of primitive fungus). Some examples of non-legumes are species of Alnus, Elaeagnus Myrica, Araucaria, Ginkgo, and Casuarina. Unlike legumes, which are largely tropical in origin, these nitrogen fixers originate in the temperate zone. Nitrogen fixation by blue green algae or cyanobacteria may take place in free living forms or in symbiosis with fungi as in certain lichens, mosses ferns and at least one seed plant. The fronds of the small free floating aquatic fern Azolla contain small pores filled with symbiotic blue green algae Anabaena that actively fix nitrogen. For centuries this fern has played an important role in the rice fields of China. Before the rice fields are planted the water filled paddy fields are covered with the aquatic fern which fixes enough nitrogen for the crop as it matures. This practice permits rice to be grown without further addition of nitrogen fertilisers. Symbiotic nitrogen fixers are more efficient than free living ones.


Related Discussions:- Symbiotic nitrogen fixers - nutrient cycles

How public perception of science has distorted, Give an example of how the ...

Give an example of how the public perception of science has been distorted or manipulated to serve an alternative purpose.

5.4 assessment from the book, Briefly explain why cutting a flatworm into p...

Briefly explain why cutting a flatworm into pieces would not kill it

Acid rain, What direct or indirect effect is acid rain thought to have on m...

What direct or indirect effect is acid rain thought to have on mama''s and forest and buildings

Advantages and disadvantages of tissue valves, Advantages of Tissue Valv ...

Advantages of Tissue Valv es   Need for anticoagulation therapy is only for a short duration in xenograft and only there is rare need for anticoagulation therapy in au

Explain iodophors, In these disinfectants, iodine is incorporated along wi...

In these disinfectants, iodine is incorporated along with a detergent. They are not as effective as hypochlorites against bacterial spore but also get inactivated in the pres

What is ascending aortic aneurysm, What is Ascending Aortic Aneurysm ? ...

What is Ascending Aortic Aneurysm ? Ascending Aortic Aneurysm :  In aneurysms confined to ascending aorta well below the innominate artery origin, the technique used is

Osteoporasis, OSTEOPORASIS - Reduction in bone tissue mass causing weak...

OSTEOPORASIS - Reduction in bone tissue mass causing weakness of skeletal strength. It leads to crush fracture. It occurs in pastmenopausal women & elderly man. Common

Accessory food substances or vitamins, Q. Accessory Food Substances or Vita...

Q. Accessory Food Substances or Vitamins ? Bacteria also vary in their need for vitamins or accessory growth factors. Some microorganisms are unable to synthesize some or all o

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

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!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd