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

Choice of graft material depends on, Choice of graft material depends on ...

Choice of graft material depends on - Its nature towards bone e.g., Osteoconductive or osteoinductive - Its architecture i.e., granular or block, pore si-e - Its origin -

Monosaccharides and disaccharides, Monosaccharides are frequently known as...

Monosaccharides are frequently known as single or simple sugars and are the easiest of all carbohydrates. That is the building blocks of all higher carbohydrates. The Monosacchari

Advantage of using the regulatory strategy of enzyme, You have two enzymes,...

You have two enzymes, 1 and 2. Both convert substance A into substance B. 1 is inhibited by B, because B partially blocks the active site and will not allow more A to enter. 2 is i

Explain about the cancer, Explain about the Cancer? The word 'cancer' c...

Explain about the Cancer? The word 'cancer' comes from the Latin for crab. It refers 90 any malignant growth or tumor caused by abnormal and uncontrolled cell division. Body ce

Find out which allele is dominant, Diagram the cross and determine which al...

Diagram the cross and determine which allele is dominant for each of the following Drosophila matings? a. Two red-eyed flies yield 110 red-eyed and 35 brown-eyed offspring.!

What is a test tube and how is it used, What is a test tube and how is it u...

What is a test tube and how is it used? A test tube is a clear, cylindrical glass tube generally open at one end and rounded at the other, used in laboratory experimentation.

State the limitations of intra oral periapical radiographs, Limitations of ...

Limitations of Intra Oral Periapical Radiographs  It is not optimal in pre operative planning of cases with severely resorbed ridges  Anatomical structure of importance can'

Use of gloves as personal protective equipment, Q. Use of Gloves as persona...

Q. Use of Gloves as personal protective equipment? Gloves are task specific. The different types of gloves worn in the dental office are: i) Examination gloves ii) Over o

Water loss - plant water relation, Water Loss - Plant Water Relation ...

Water Loss - Plant Water Relation Plants lose about 98% of water to the atmosphere by transpiration. Often water loss by transpiration exceeds gain by absorption and results

Bladder worm, what is the function of the bladder in the bladder worm

what is the function of the bladder in the bladder worm

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