Tag: ecosystem

Photosynthetically active radiation or PAR is, the spectral range (wave band) of solar radiation from 400 to 700 nanometers. At this range, an autotroph synthesises the food by the process of photosynthesis. Hence option B is correct.

Photosynthesis occurs in small portion of spectrum, called as 'photosynthetically active radiation' or PAR (400-700 nm). Maximum absorption of light occurs in blue region (around 400 nm) followed by red light (around 700 nm). Maximum photosynthesis, however, occurs in red light. Least photosynthesis occurs in green light.

The photosynthesis process is essentially a light dependent synthetic process, which results in synthesis of sugars. A small part of the solar spectrum in the visible portion is used in the process of photosynthesis. This small portion of the solar spectrum is called photosynthetically active radiations or PAR. The wavelength of light active in PAR occur between 400 to 700 nm.

Blue light of the spectrum is absorbed more for the process of photosynthesis. Plants have two types of chlorophylls - a and b. Chloropphyll a is a specific form of chlorophyll used in oxygenic photosynthesis. It absorbs most energy from wavelengths of violet-blue and orange-red light. A yellow-green chlorophyll pigment which occurs only in plants and green algae. It functions as a light harvesting pigment that pass on the light excitation to chlorophyll a. It absorbs well at wavelength of 450-500 nm and 600-650 nm.

Chlorophyll absorbs red and violet-blue light, while transmitting and reflecting green light. Chlorophyll 'a' absorbs blue light with wavelengths of 430 nm and red light of 662 nm. 453 nm and 642 nm wavelengths are absorbed by chlorophyll 'b'.

Theodor Wilhelm Engelmann was a German botanist, phsiologist, microbiologist, university professor and musician, whose 1882 experiment measured the effects of different colours of light on photosynthetic activity and showed that the conversion of light energy to chemical energy took place in the chloroplast. Both blue and red wavelength are effective because the amount of oxygen released was found to be maximum in blue and red absorption bands of the chlorophyll.

Small part of visible light in the range of 400 to 700 nm is active in photosynthesis. It is called as photosynthetically active region or PAR. The chlorophyll absorbs maximum in the blue region and red region. The blue region of PAR is near 400 nm after violet and indigo light, while the red region is near 700 nm. The blue region is centered around 460 nm, where chlorophyll a shows maximum absorption.

During photosynthesis 1 to 4% light is utilized. Photosynthesis is more in intense light and is also counted as a limiting factor. Without enough light, a plant cannot photosynthesise very quickly, even if there is plenty of water and carbon dioxide. Increasing the light intensity will boost the speed of photosynthesis.

An ecological efficiency is the efficiency of energy transfer from one trophic level to the next trophic level. In other words, it is the energy in biomass production at a trophic level divided by energy in biomass production at previous trophic level. It is the ratio of energy flows at different trophic levels in a food-chain. It is expressed in percentage.

Wavelength of light absorbed during photosynthesis is 440 nm (violet to blue light). It is the main function of chlorophyll molecule, which is called as the photosynthetic pigment. the violet, blue light have shorter wave length and higher energy content.