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

How to identify the metal out of which the wire is made, A wire 50.0 m long...

A wire 50.0 m long and 2.00 mm in diameter is connected to a source with a potential difference of 9.11 V, and the current is found to be 33.7 A. Assume a temperature of 20°C and,

Explain dehydration, Explain Dehydration Dehydration is one of the anc...

Explain Dehydration Dehydration is one of the ancient food processing techniques.  Dehydration means to completely remove water under controlled  conditions, in such a way

AMOEBA, mORPHOLOGY OF AMOEBA AND ITS ADAPTATIONS

mORPHOLOGY OF AMOEBA AND ITS ADAPTATIONS

Define food components other than essential nutrients, Define Food Componen...

Define Food Components Other Than Essential Nutrients? In the previous units so far, we have read about the six major nutrients, which are essential for us. Though these vary i

Pachytene, Pachytene: The pairing of homologous chromosomes is comp...

Pachytene: The pairing of homologous chromosomes is completed. Chromosomes become more and more thick. Each bivalent has four chromatids , which wrap around each o

Explain the ecg and cheast x- ray, Explain The ECG and cheast X- Ray? ...

Explain The ECG and cheast X- Ray? The ECG and Chest X-ray: If there is a suspicion of heart disease on basis of the history or physical examination an ECG and a chest X-ray

What are enzymes, What are enzymes? What is the importance of enzymes for l...

What are enzymes? What is the importance of enzymes for living beings? Enzymes are proteins that are catalysts of chemical reactions. From Chemistry it is called that catalysts

Explain the importance of the auxin, a) How is the milk production regulate...

a) How is the milk production regulated by hormones in human female? Define. b) Explain the importance of the auxin / cytokinin ratio in plant tissue culture.

Determine the bioavailability of minerals, Bioavailability of Minerals ...

Bioavailability of Minerals It is well known that the concentration of a nutrient in a food is not a reliable indicator of its nutritional value. In other words, the entire qua

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