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

#zoology, #what is naturalistic theory?

#what is naturalistic theory?

What is the difference between macro and micronutrients, What is the differ...

What is the difference between macro and micronutrients? The categorization criterion of nutrients into macro and micronutrients has no relation to the size of the molecule. M

Ecology, three types of trophic pyramids

three types of trophic pyramids

How the average number of offspring raised to adulthood, Researchers (Helle...

Researchers (Helle et al., 2004) analyzed rates of twin births in the Sami population of Northern Scandinavia during the eighteenth and nineteenth centuries. They found that (1) a

Explain the periapical surgery - endodontic surgery, Explain the Periapical...

Explain the Periapical surgery - Endodontic Surgery a) Curretage 1 b) Root-end ressection 2 c) Root-end preparation 3 d) Root-end filling 4

Secondary prevention - rheumatic fever, Benzathine penicillin given every t...

Benzathine penicillin given every three weeks as IM injection (1.2 mega units) has given the best results. Oral agents (penicillin V) are given in patients with lower risk of rheum

Which are the phases of the menstrual cycle, Q. Which are the phases of the...

Q. Which are the phases of the menstrual cycle? The menstrual cycle is divided into two major phases: the luteal (or secretory) phase and the follicular (or menstrual) phase.

What is the commercial importance of algae, Q. What is the commercial impor...

Q. What is the commercial importance of algae? Numerous algae have high nutritional value and are commercialized and consumed as human food they are very popular food in the or

What essential function do they serve, Why do membranes figure so prominent...

Why do membranes figure so prominently in eukaryotic cells? What essential function do they serve?

Define resolution - terminologies used in chromatography, Define Resolution...

Define Resolution - terminologies used in chromatography? Resolution is the effectiveness of the separation and is determined by two factors. These include: Distance

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