Light and distribution, Biology

Assignment Help:

Light and Distribution

We have mentioned in the beginning that the variation in the amount of light generally affects the global and local distribution of plants and animals. Light plays a great role in species composition and development of vegetation. We have already discussed the global variation of light intensity. Let us study the causes of variation in light climate in terrestrial and aquatic ecosystem. In order to provide a comprehensive idea of light climate of any locality, information on the following three aspects needs to be provided:

i) Intensity or amount of light per unit area per unit time,

ii) The quality or wavelength composition, and

iii) Photoperiod or duration.

Significant local variation in the light in the terrestrial ecosystems results due to the interception of light by vegetation. In a forest, tall trees with fully expanded canopy receive maximum sunshine and absorb a major portion of the incident light especially in the red and blue regions. The undershrub and herb layers receive only light filtered through the tree canopy from above. In a thick forest the light interception by the multistoreyed vegetation is very efficient and on the forest floor light intensity may be only 1% of the incident solar radiation received at the top of the canopy.

Due to selective absorption, spectral light quality changes as it passes through the tree canopies. Yet, we find that some plant species are adapted to functioning in such low light intensities. On the basis of relative preference for natural growth in bright or diffused light the plants have been classified into two categories - sciophytes (shade loving) and heliophytes (bright-light loving). Some plants are more rigid in their preference for shade or bright light. These are termed as obligate sciophytes and obligate heliophytes respectively. There are some heliophytes that can also grow in shade but not so well. These are called facultative sciophytes. Similarly, the sciophytes that can also grow in bright light are called facultative heliophytes.

Plants can survive only when the total energy harnessed in photosynthesis exceeds that used in respiration. The intensity of light at which energy harnessed through photosynthesis is just sufficient to meet the energy requirement of respiration is called light compensation point. In deep shade, under trees the amount of light is not enough to carry on photosynthesis to satisfy the immediate need of the plants. Therefore, they lose leaves and usually branches. The leaves in a tree canopy are arranged in a way so as to function above light compensation point.


Related Discussions:- Light and distribution

How vitamin k used to prevents bone loss, How Vitamin K used to Prevents bo...

How Vitamin K used to Prevents bone loss? Vitamin K is known to inhibit bone loss through inhibiting effect on osteoclast formation. Thus, adequate levels of vitamin K must be

Thermodynamics and cell shapes, Thermodynamics and Cell Shapes Why are...

Thermodynamics and Cell Shapes Why are protoplasts (cells devoid of cell wall) spherical? Why are most of the unicellular organisms (prokaryotes and eukaryotes) spherical? A s

Explain the toxicity of vitamin d, Explain the Toxicity of Vitamin D? ...

Explain the Toxicity of Vitamin D? The adverse effects of high vitamin D intakes include hypercalciuria (excessive urinary calcium excretion) and hypercalcaemia (high concentr

Explain effect of irradiation on nutrients, Normal 0 false fa...

Normal 0 false false false EN-IN X-NONE X-NONE MicrosoftInternetExplorer4

What is the control center of the cell, What is the control center of the c...

What is the control center of the cell? The nucleus contains DNA, which having the instructions for all the functions of the body.

Adrenaline and noradrenaline, Both these neurotransmitter strengthen memory...

Both these neurotransmitter strengthen memory when they are released into the blood stream following learning. Stressful events stimulate release of stress hormones from the adrena

What is a community, What is a community? What is the difference between th...

What is a community? What is the difference between the concepts of community and population? A community is a set of the populations of living beings that live in the same reg

Determine the term -stolon, Determine the term -Stolon. In a number of ...

Determine the term -Stolon. In a number of colonial cnidarians, ascidians, and lophophorans, a cord of tissue connects different zooids of colony to each other. Buds on stolon

Monoclonal antibody, Monoclonal Antibody is an antibody with quite specifi...

Monoclonal Antibody is an antibody with quite specific and often unique binding specificity which is secreted by the biologically cloned line of plasmacytoma cells in the absence

Define nutritional requirements for extreme environments, Define Nutritiona...

Define Nutritional Requirements for Extreme Environments? Human beings have been able to survive and work under extreme environments of almost all regions of the earth, from po

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