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

What are the major functions of the blood, Q What are the major functions o...

Q What are the major functions of the blood? The blood is a means of substance transportation throughout the body. The blood distributes hormones, nutrients, oxygen, cells and

What is an operon, What is an operon, and in what type of organism are oper...

What is an operon, and in what type of organism are operons found? An operon is a series of genes that code for exact products and the regulatory elements that control those ge

Elaborates the pathophysiology of ventricular septal defect, Elaborates the...

Elaborates the Pathophysiology of ventricular septal defect? The shunt in the VSD is left to right. The magnitude of the shunt is determined by the size of the VSD and the, lev

Diffrence between fish epidermis and amphibian epidermis, Q. How different ...

Q. How different is the fish epidermis from the amphibian epidermis? The fish epidermis is very contains and thin mucus-secreting cells the fish skin doesn't present keratin, t

What are the amphibian features, Q What are the amphibian features that mak...

Q What are the amphibian features that make them dependent on water to survive? Permeable skinexternal fecundation, body subject to dehydration, larval stage and eggs without s

Pisces, what is the mode of nutrition in pisces

what is the mode of nutrition in pisces

Mycotic diseases, Mycotic diseases Mycotic (fungal) diseases of animal...

Mycotic diseases Mycotic (fungal) diseases of animals and birds are of considerable importance both from public health and economic point of view. The fungi responsible for an

Calculate concentration of solution from standard curve, Calculate the Conc...

Calculate the Concentration of Unknown Solution from Standard Curve? i) First take different volume of standard solution (say 0.2, 0.4, 0.6, 0.8, 1.0 ml) and then calculate the

What is transgenesis - molecular biology, Molecular Biology - transgenesis ...

Molecular Biology - transgenesis Difficult to successfully insert the gene then successfully re-implant embryo possible pleiotropic effects low success rate / tak

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