In this article we will about the importance of sunlight in an ecosystem.
Sunlight is a major part of abiotic conditions in an ecosystem. The sun is the primary source of energy on our planet. Above infrared in frequency comes visible light. The Sun emits its peak power in the visible region, although integrating the entire emission power spectrum through all wavelengths shows that the Sun emits slightly more infrared than visible light.
Visible light is the part of the EM spectrum to which the human eye is the most sensitive. Visible light (and near-infrared light) is typically absorbed and emitted by electrons in molecules and atoms that move from one energy level to another.
The light which excites the human visual system is a very small portion of the electromagnetic spectrum. A rainbow shows the optical (visible) part of the electromagnetic spectrum; infrared (if you could see it) would be located just beyond the red side of the rainbow with ultraviolet appearing just beyond the violet end.
Electromagnetic radiation with a wavelength between 380 nm and 760 nm (400-790 terahertz) is detected by the human eye and perceived as visible light. Other wavelengths, especially near infrared (longer than 760 nm) and ultraviolet (shorter than 380 nm) are also sometimes referred to as light, especially when the visibility to humans is not relevant.
White light is a combination of lights of different wavelengths in the visible spectrum. Passing white light through a prism splits it up in to the several colors of light observed in the visible spectrum between 400 nm and 780 nm. Light energy (sunlight) is the primary source of energy in nearly all ecosystems.
It is the energy that is used by green plants (which contain chlorophyll) during the process of photosynthesis; a process during which plants manufacture organic substances by combining inorganic substances.
Visible light is of the greatest importance to plants because it is necessary for photosynthesis and rest of the solar energy either reflected or absorbed by atmosphere. Factors such as quality of light, intensity of light and the length of the light period (day length) play an important part in an ecosystem.
(i) Quality of Light (Wavelength or Colour):
Plants absorb blue and red light during photosynthesis. In terrestrial ecosystems the quality of light does not change much. In aquatic ecosystems, the quality of light can be a limiting factor. Both blue and red light are absorbed and as a result do not penetrate deeply into the water. To compensate for this, some algae have additional pigments which are able to absorb other colours as well.
(ii) Light Intensity:
The intensity of the light that reaches the earth varies according to the latitude and season of the year. The southern hemisphere receives less than 12 hours of sunlight during the period between the 21st March and the 23rd of September, but receives more than 12 hours of sunlight during the following six months.
(iii) Phototropism:
Phototropism is the directional growth of plants in response to light where the direction of the stimulus determines the direction of movement; stems demonstrate positive phototropism i.e. they came towards the light when they grow.
