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

Define nutrition management and feeding the premature infant, Define Nutrit...

Define Nutrition Management and Feeding the Premature Infant There are numerous nutritional risk factors in premature infants. These include: Elevated metabolic rate, th

History of protoplasm, HIS T O R Y - Protoplasm was first seen b...

HIS T O R Y - Protoplasm was first seen by Corti, 1772 F . Dujardin called it "Sarcode" & observed it in animal cell Term "Protoplasm" was given by J.E. Pu

Is pollution always caused by humans, Q. Is pollution always caused by huma...

Q. Is pollution always caused by humans? In the most cases pollution is caused by human activity. Other species and some abiotic factors though can also pollute an ecosystem. F

Gonad glands, what are the gonad gland disorders and what do they do

what are the gonad gland disorders and what do they do

What is a population, What is a population? A population is a set of in...

What is a population? A population is a set of individuals of the similar species found in a given place in a given time.

Infectious laryngotracheitis, I nfe c tio u s laryngotracheitis It...

I nfe c tio u s laryngotracheitis It is a slow, laterally spreading respiratory disease of chickens, pheasants, peafowl and turkeys caused by a herpes virus with high morb

Temperate evergreen forest - ecosystem, Temperate evergreen forest - Ecosys...

Temperate evergreen forest - Ecosystem Many parts of the world have a mediterranean type of climate which is characterised by warm, dry summers and cool, moist winters. These

Pair of alleles has different allelesdominance between them, Whenever a pai...

Whenever a pair of alleles has different alleles is there dominance between them? Not in all cases of a gene includes two different alleles is the dominance complete. There are

Explain the term- pupil, Explain the term- PUPIL Pupil is  the  apertu...

Explain the term- PUPIL Pupil is  the  aperture in  centre of  the  iris diaphragm that regulates entry  of  light into the eye. Colour of  pupil  is  said  to be  black. Actu

Palaeontological evidence of evolution, EVIDENCES OF EVOLUTION - The ev...

EVIDENCES OF EVOLUTION - The evidences of organic evolution derived from many lines of study indicate that present day forms have arisen by gradual changes from pre existing fo

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