Crustose lichen stage - xerarch, Biology

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.

Posted Date: 1/21/2013 12:24:31 AM | Location : United States







Related Discussions:- Crustose lichen stage - xerarch, Assignment Help, Ask Question on Crustose lichen stage - xerarch, Get Answer, Expert's Help, Crustose lichen stage - xerarch Discussions

Write discussion on Crustose lichen stage - xerarch
Your posts are moderated
Related Questions
hows does insulin from the pancreas reach the liver?

Explain Pasteurization (temperature below 100° C) - method of food preservation? Pasteurization is a heat treatment that kills a part but not all the microorganisms present and

Domestic Effluents - Causes of Water Pollution Liquid waste produced daily in kitchen, bathroom and toilet are discharged directly or through canal, river or any other water b

State two characteristics of humans which distinguish them from other primates. Two features which differentiate humans from other primates are their upright posture and their

What are two specific organs that work together to preform a function??

Does seed germination affect plant growth? Germination does affect plant growth Without germination in the plant, the plant is not capable to grow. The germination is the st

The need to replace missing teeth has haunted humans for time immemorial. Since antiquity man has attempted to solve the problems associated with failing dentition. The goal of mod

System of classification The Enzyme Commission divided enzymes into 6 main classes, on the basis of the total reaction catalyzed. Each enzyme was assigned a code number; consis

What is the salivary digestive enzyme? Which type of food does it digest and into which smaller molecules does it transform the food? The salivary hydrolase is called as saliva

What is the Importance of pantothenic acid One of the active forms of pantothenic acid is coenzyme A, which is involved in numerous metabolic functions. It is involved in t