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

State the term - molybdenum, State the term - Molybdenum   Molybdenum i...

State the term - Molybdenum   Molybdenum is intimately related to nitrogen metabolism of plants. It is part of the nitrate reductase system which helps to utilise nitrate for n

State the young''s trichromatic theory, Young's Trichromatic Theory Ac...

Young's Trichromatic Theory According to Young's theory, three types of cones exist, each sensitive to a particular pigment-rythrolabe (red), chlorolabe (green), and cyanolabe

Animal diversity, what are the theories of animal classification

what are the theories of animal classification

Explain about ecological species concept, Q. Explain about Ecological speci...

Q. Explain about Ecological species concept? The ecological species concept: This identifies a species as a population that occupies a distinct ecological niche, whence its rep

Protoplast, PROTOPLAST Cell without cell membrane (Henstein) It c...

PROTOPLAST Cell without cell membrane (Henstein) It contains 1 or more vacuoles. In mature plant cells protoplast forms a peripheral layer called Primordial utricle.

Provide the definition of health care, Provide the Definition of Health Car...

Provide the Definition of Health Care? Health care involves much more than just medical care and can be defined as "multitude of services provided to individuals or communities

Enumerate the term - pathognomic sign, Enumerate the term - pathognomic sig...

Enumerate the term - pathognomic sign A comprehensive assessment ideally uses all four approaches. Some forms of specialised assessment rely heavily on pathognomic signs, behav

Determine the food sources of pyridoxine, Determine the Food Sources of Pyr...

Determine the Food Sources of Pyridoxine? Raw foods contain more of this vitamin than cooked foods. The food sources include: 1. Rich sources: Rice polishing s, wheat bran,

Anatomy, what is the longest cell in human body

what is the longest cell in human body

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