What is light? What may be your answer when you are suddenly confronted with this question? Surely it would not be a surprise if the question elicits a shocking, caught-in the-act, stammering realization to many persons.
Oftentimes the automatic answer is the funny “Well, light is light!” But this answer should not be a surprise too. Light has always been there, and we live day after day without finding the necessity to know further what is light or what is the definition of light.
It’s quite different in studying the science of crop production. To find ways to improve crop productivity, it is important to be able to acquire sufficient understanding of photosynthesis, as well as other photo-processes. It means understanding also the different factors that will promote efficient photosynthesis. The root word ‘photo’ means light.
Light performs a major function in plant growth and development. It is essential in the production of energy that sustains life through the process of photosynthesis. In addition, it influences or controls other plant growth processes such as the synthesis of the different photoreceptors (e.g. chlorophyll, other pigments), photomorphogenesis (organ formation and development), phototropism (plant response to unilateral light), photoperiodism, translocation, mineral absorption, and transpiration. To better understand these functions, it is necessary to acquire sufficient background on what is light including its various properties.
Various sources provide many meanings or definitions of light. Here are some entries:
The herein author of this and companion pages prefers the definition of light given by Moore et al. (2003). It clearly describes light as visible to the naked eye, one which even primary graders can comprehend. To those with more advanced perception, the reference to "electromagnetic spectrum" and the given "about" wavelengths that elicit visibility are also valuable giveaways. For a more relevant introduction to climatic factors affecting plant growth and development, it would be appropriate also for the one explaining that this light "controls or influences plant growth and development processes”.
Energy is the ability to do work, that is, to bring about change or to move matter against an opposing force. There are various forms of energy: potential and kinetic; chemical, gravitational, nuclear, mechanical, electrical, sound, radiant (electromagnetic), and thermal (heat) energy.
The radiant energy from the sun, or solar energy, is transformed into chemical energy through the process of photosynthesis. It is stored in the bonds that hold atoms together, as in food that provides the energy to perform mechanical work. In these cases there is convertion from one form of energy to another in accordance with the first law of thermodynamics: Energy can be converted from one form to another, but it cannot be created or destroyed.
However, most of the solar energy is absorbed or reflected back to the atmosphere and becomes heat. The following summary of the fate of the solar energy by Mader (1990) further provides more elaboration on what is light:
(1) Only 42% reaches the surface of the earth; (2) of this, most becomes heat and only about 2% is finally utilized by plants; (3) of this 2%, only 0.1-1.6% is incorporated into plant tissues; (4) of this, only 20% is eaten by herbivores, of which 30% is eaten by carnivores.
When used by organisms, the energy in food is ultimately converted to
heat upon death and decay and released to the atmosphere. A large proportion of
the energy in plant and animal tissues is stored in the fossil fuels that are
burned to provide heat energy.
(Ben G. Bareja Sept. 2012)
Apr 06, 19 04:31 AM
Reviews the existence of plant sex with some notes leading to its discovery by Camerarius.
Apr 05, 19 10:52 AM
Some of the major factors to consider in crop selection are discussed with the assumption that a farm is already available.
Apr 02, 19 11:23 AM
Cover crops have numerous benefits, also as source of forage and as groundcover in landscaping.