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

Tagmatization, sample assignment on tagmatization

sample assignment on tagmatization

What is gene expression, What is Gene Expression ? Gene expression i...

What is Gene Expression ? Gene expression is the process by which a gene is activated to produce a certain protein. Cells are able to respond to changes in the environment i

Classification of freshwater ecosystems, Classification of Freshwater Ecosy...

Classification of Freshwater Ecosystems Fresh water ecosystems depend on the terrestrial ecosystems for large quantities of organic and inorganic matter which are constantly a

Metabolic cataysis, Metabolic Cataysis A large number  of chemical reac...

Metabolic Cataysis A large number  of chemical reaction  occur  every  moment in a cell  to keep it. In the living  state, The rate  if  chemical  reaction normally depends upo

Define requirements of calcium during pregnancy period, Define requirements...

Define requirements of Calcium during pregnancy period? The foetus retains about 25-30 g of calcium, over the course of gestation, most of which is deposited in the last trimes

Determine the categories of sleep disorders, Determine the categories of sl...

Determine the categories of sleep disorders Sleep disorders are generally divided into two major groups: 1) Narcolepsy, which is characterised by excessive sleep or brief in

Cori cycle, Cori Cycle Skeletal muscles have some mitochondria, yet are...

Cori Cycle Skeletal muscles have some mitochondria, yet are competent of vigorous activity. as a output, the little stores of oxygen are rapidly depleted, causing the muscle ti

Explain bleeding on probing, Bleeding on Probing (BOP) BOP when elicite...

Bleeding on Probing (BOP) BOP when elicited (notated in patient record as BOP +) after the insertion of a probe into the sulcus with light pressure i.e. 25 N has been shown to

Locomotion in star fish, LOCOMOTION IN STAR FISH - With the help of tub...

LOCOMOTION IN STAR FISH - With the help of tube feet aided by fluid pressure in them. In a tube feet upper ampulla, middle podium and lower sucker present.

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