Light and distribution, Biology

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.

Posted Date: 12/10/2012 6:15:07 AM | Location : United States







Related Discussions:- Light and distribution, Assignment Help, Ask Question on Light and distribution, Get Answer, Expert's Help, Light and distribution Discussions

Write discussion on Light and distribution
Your posts are moderated
Related Questions

Explain fats requirements during thyphoid Fats: Use of fats should be in moderation. This is because the typhoid patient has a compromised ability to digest and assimilate due

Define Importance of Nutrition in Human Body? Nutrition is increasingly being recognized as an important determinant, which modulates the biological process of ageing. Poor nut

State the Continuous sutures Suturing technique It can be used to attach 2 surgical flap edges or to secure multiple interproximal papillae of one flap independently of the oth

Name the three irreversible reactions  in the glycolytic pathway. The three irreversible reactions in the glycolytic  pathway are : Glucose → Glucose-6-phosphate Fructose

Protection of our property:                  ·          If any our property lies in an area prone to landslides, we should seek advice of experts in earth movement and take cor

some deliveries of baby occur early na. y is it so?

Q. Explain about Individual consciousness? The physical brain is not a source of experience as some current neuroscientists now mistakenly believe. While areas of the brain are

What is Dinoflagellates ? Dinoflagellata or dinoflagellates , are characteristically unicellular photosynthetic organisms that usually have two flagellae. One flagellum typi

Do disinfectants kill bacteria? Secure various types of commercial and house- hold disinfectants. Inoculate as more culture dishes as you have samples of disinfectant and singl