Effect light in greenhouse ppt

2. The greenhouse effect refers to circumstances
where the short wavelengths of visible light from
the sun pass through a transparent medium and
are absorbed, but the longer wavelengths of the
infrared re-radiation from the heated objects are
unable to pass through that medium.

3. Light is measured differently depending on what
part of the light spectrum is being measured. The
total light spectrum coming from the sun (400 to
1100 nanometer wavelengths) is measured in
units of watts/m2. On a clear sunny summer day,
there may be 1000 Watts/m2.

4. The amount of light entering a greenhouse is
influenced by;
the orientation of the structure
the materials used in construction and covers
the shape of the roof.

5. A balance of light across the PAR range is
considered to be preferable, however there is
increasing research being conducted in the area
of light spectrum modification for improved plant
growth.

6. The colour of plastic films affects the total level of
light that enters the greenhouse.
A clear film will transmit the most amount of light.
Blue and green coloured plastics will transmit a
lot of the light in the blue to blue-green
wavelengths, but cut out much of the light in the
red wavelengths.

7. Plants have an optimal intensity of light. This is
the point at which the process of photosynthesis
is maximised and plant growth is greatest. If the
level of light is less, growth is reduced. The point
where an increase in light intensity will not
increase photosynthesis any more is called light
saturation.

8. Low light slows growth and increases the cost of
production but excessive light intensity can
damage some plants and/or fruit. Light is
increased by minimising objects above the plants
including frames, pipes, lights and other
equipment. The level of radiation entering a
greenhouse can be reduced with screening
materials.

9. Supplementary lighting is not considered to be
economical for producing most crops in Australia,
however, supplementary light may be used to
improve seedling uniformity during propagation.

10. The increase in the concentration of carbon
dioxide, one of the three major atmospheric
contributors to the greenhouse effect has been
carefully documented at the Mauna Loa
Observatory in Hawaii. The 1990 rate of increase
was about 0.4% per year. The interesting cyclic
variations represent the reduction in carbon
dioxide by photosynthesis during the growing
season in the northern hemisphere.

11. The increase in the concentration of carbon
dioxide, one of the three major atmospheric
contributors to the greenhouse effect has been
carefully documented at the Mauna Loa
Observatory in Hawaii. The 1990 rate of increase
was about 0.4% per year. The interesting cyclic
variations represent the reduction in carbon
dioxide by photosynthesis during the growing
season in the northern hemisphere.

12. Those gas molecules in the Earth's atmosphere
with three or more atoms are called "greenhouse
gases" because they can capture outgoing
infrared energy from the Earth, thereby warming
the planet. The greenhouse gases include water
vapor with three atoms (H2O),

13. http://hyperphysics.phy-astr.gsu.edu/
https://www.dpi.nsw.gov.au/