Crustose lichen stage - xerarch, Biology

Assignment Help:

Crustose Lichen Stage - Xerarch

On bare rocks, conditions are inhospitable for life, as there is extreme deficiency of water and nutrients, great exposure to sun, and extremes of temperature. Crustose lichens alone are usually able to grow in such situations. Some examples of these pioneering species are, Rhizocarpon, Rhinodina, Lecidea and Lecanora. These plants flourish during periods of wet weather and remain in a state of desiccation for very long periods during drought. During the wet weather they rapidly absorb moisture by their sponge-like action. Mineral nutrients are obtained by the secretion of carbon dioxide which, with water forms a weak acid that slowly eats into the rock into which the rhizoids sometimes penetrate for a distance of several millimetres.

Nitrogen is brought by rain or by wind-blown dust. Thus all the life requirements of this simple, crust-like species is met with. Thus, lichens help corrode and decompose the rock, supplementing the other forces of weathering. And by mixing the rock particles with their own remains, make conditions favourable for - growth of other organisms. Thus, a thin layer of soil is formed. The rapidity with which a small amount of soil is formed is controlled largely by the nature of the rock and by the climate. On quartzite or basalt rocks in a dry climate, the crustose-lichen stage might persist for hundreds of years. But on limestone or sandstone in a moist climate, sufficient changes permit the invasion of foliose lichens, and all this may occur within a life time.


Related Discussions:- Crustose lichen stage - xerarch

Assessment of infective endocarditis, Assessment   Infective endocardit...

Assessment   Infective endocarditis  is characterised  by insidious onset of fever, malaise, night- sweats and weight loss. Other signs include vomiting, fatigue, headache, mya

Heat removal of gutta percha-endodontics principles, Heat removal of Gutta ...

Heat removal of Gutta percha: -    Heated plugger. -    Touch-N-Heat or system B used to thermo soften and remove gutta-percha from root canal systems. -    The cross-sectional

What are the androecium and the gynoecium, What are the androecium and the ...

What are the androecium and the gynoecium? What are the other structures of flowers? Androecium is the set of male reproductive structures of flowers. It comprehends the stamen

Osmosis, everything about osmosis

everything about osmosis

steps of c-dna creation and mrna, C dna is made from a mature m rna of euk...

C dna is made from a mature m rna of eukaryotic cell with the utilization of enzyme called as reverse transcriptase. Steps in c dna creation 1. m rna is made and purified f

Preventive measures of rheumatic fever, Preventive Measure Primary p...

Preventive Measure Primary prevention Early detection and treatment of group "A" b-hemolytic streptococcal pharyngitis. Penicillin is the commonly prescribed drug. Educ

How cells of neoplastic tumors obtain oxygen and nutrients, Q. How do cells...

Q. How do cells of neoplastic tumors obtain oxygen and nutrients and release wastes? In the neoplastic tumors a phenomenon called as angiogenesis occurs. The Angiogenesis is th

Indicators of disability burden: qalys/dalys, Normal 0 false ...

Normal 0 false false false EN-IN X-NONE X-NONE MicrosoftInternetExplorer4

Explain scope of food science and technology as a subject, Explain Scope of...

Explain Scope of Food Science and Technology as a Subject? Food science and technology has developed as a discipline to systematically organize and link various kinds of knowle

How many of each type of core histone, How many of each type of core histon...

How many of each type of core histone would it take to wrap the entire human genome into nucleosomes? How has evolution solved the problem of producing such a large number of prote

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