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 ecosystems science and large-scale ecology, Define Ecosystems scienc...

Define Ecosystems science and large-scale ecology? Many of today's most pressing problems are regional or global in nature including for instance, the effects of land cover and

What are the vitamins which make up the b complex, Q. What are the vitamins...

Q. What are the vitamins which make up the B complex? Which problems does the lack of these vitamins cause? Vitamins of the B complex are: vitamin B1 or thiamin, riboflavin, or

Types of cambium, Types of Cambium On the basis of the arrangement of ...

Types of Cambium On the basis of the arrangement of the Fusiform cells as seen in tangential section, cambium is divided into: A) Storied/Stratified Cambium : The groups o

Patient care plan for hypertensives, Q. Patient care plan for hypertensives...

Q. Patient care plan for hypertensives? - Lifestyle changes: Avoiding smoking, use of tobacco, and excess alcohol intake Physical activity like walking, 4 times a week or 40 mi

Describe the mechanism use to alleviate situation, If levels of ATP become ...

If levels of ATP become high in a cell (i.e more than the cell needs at that time), describe the mechanism that the cell would use to alleviate this situation (include the name of

Explain phyium oomycetes, Phyium Oomycetes 1) They reproduced asexually...

Phyium Oomycetes 1) They reproduced asexually by non-motile conidia and/or mobile flagellatedzoospores. 2) The sexual reproduction is by fusion of a male gamete with an egg

Explain about vascular cambium, How can the age of a tree be estimated from...

How can the age of a tree be estimated from the analysis of the rings present on a cross section of its stem? For the growth of the tree it is essential to have formation of ne

Protein, What''s the classification of simple protein?

What''s the classification of simple protein?

Illustrate adaptation to terrestrial life, Q. Why can the allantois be cons...

Q. Why can the allantois be considered an adaptation to terrestrial life? The allantois is an adaptation to dry land because in embryos of oviparous terrestrial beings like bir

Pectin, PECTIN It consists of methylated galacturonic acid, galactos...

PECTIN It consists of methylated galacturonic acid, galactose & arabinose. It is also called plant cement becuase it binds layers of cell wall. It is a structural poly

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