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Transcript of Biology 1
A process where carbon dioxide from the air, and water from the soil are
united by the leaves of plants to form starch through the presence of
sunlight on the green colouring matter in leaves is called photosynthesis
There are several factors affect the photosynthesis, some of these are the availability of water, light, carbon
dioxide, time and temperature. Since light plays a big role in the photosynthesis, the group decided to study the
effect of light intensity on the rate of photosynthesis by using sodium bicarbonate known as baking soda as a
source of carbon dioxide in the form of Hydrilla plants.
According to Reece (2011), photosynthesis is when the chloroplasts of
plants capture the light that comes from the sun and was converted to
chemical energy that is stored in sugar and other organic molecules.
Light is very essential in the photosynthesis as it favours the
production of chlorophyll, an agent in the making of organic carbon
compounds.Chlorophyll obtained on chloroplasts absorbs light rays
and the energy obtained is used to produce sugar and oxygen (Bailey,
Sodium bicarbonate (NaHCO3), a white water soluble crystals with an
ability to lose carbon dioxide at 270 degree Celsius; used as a medicine and a
preservative preparation in effervescent salts and beverages to prevent timber mold
(Parker, 1986). While the plant used is hydrilla (Hydrilla vericillata) is a submerged
aquatic plant that is the sole member of the genus Hydrilla. It is a fast-growing, hardy
weed that has long slender stems that grow to several feet in length and form
tangled carpets of vegetations beneath the water surface (The New Encyclopedia
Statement of the Problem
How will the intensity of light affect the rate of photosynthesis of a
Review of related Literature
Statement of the hypothesis
As you increase the intensity of light, the rate of photosynthesis should also increase.
to define photosynthesis;
to enumerate factors that affect
to determine how the intensity of light affects the photosynthesis;
The validity of the study that the light intensity will have an effect on the rate of photosynthesis was obtained from the experiment where the water plant
is submerged in a glass jar under a glass funnel.
The set-up with the stem covered by a test tube was inverted and filled with water. The apparatus is set in the sun and
bubbles of gas will rise in the funnel and be collected in the
tube. These gases formed were proven to be oxygen
It lead to our experiment which test the intensity of light to the rate of
photosynthesis by using baking soda which will fasten the reaction. Two hydrilla were placed on four test tubes with the solution of water and baking soda. The formation of bubbles was observed to know the production of oxygen. Faster formation of bubbles show faster rate of photosynthesis.
to conduct an experiment to test the hypothesis using test tubes with
hydrilla set-up; and
to conclude on the relationship and
effect of light intensity and
In determining the effect of light intensity to the plant’s photosynthetic activity, four test tubes with Hydrilla plant were used.
The test tubes were filled with 60 ml of distilled water and also added a 2.0 g of Baking Soda
(NaHCO3) in set-up.
The solutions were mixed gently, and then the Hydrilla plant was placed inside the test tubes.
The test tubes were placed in a rack but the first three were exposed to
light bulbs with different light intensities. The intensity of the
light bulbs was 10, 40, and 60 watts. The fourth
set-up was the control.
A timer was used to time the entire experiment. The bubbles formed by
the hydrilla plant were counted manually and recorded on the table. A graph was also constructed to show the relationship between the light
intensity and the number of bubbles formed by the hydrilla plant.
Results and Discussions
The four test tube set-ups after ten minutes
Summary and conclusions
The effect of the intensity of light on the rate
of photosyntesis was determined. Lamps with different watts consumption were the light source chosen for
The Effect of the intensity of light on the
rate of photosynthesis
As the light intensity increases, the rate
of photosynthesis also increases. However, there is a point where light
intensity will no longer affect the photosynthesis rate.
That point is known to be the light saturation point.
At this point, increasing the intensity of
light no longer cause an increase in the rate of
A plant will be unable to harvest light
at high intensities because the plant's chlorophyll
system can be damaged. Moreover, the number of
light absorbing pigments, chlorophyll, may not be
enough to absorb more light.
Three test tube set-up, filled with 60ml of distilled water, 2.0g of baking soda, and three hydrilla plant, were
then exposed to lamps with different watts, 20w, 40w, and 60w, while one test tube of the same set-up
was not exposed into any lamp to serve as the control set-up.
For ten minutes,
the number of bubbles
formed was counted and
Therefore, the intensity of light is directly proportional to the rate of
photosynthesis up to the light saturation point. However, there are other factors that
influence the rate of photosynthesis. Further experiments may be done on the
effect of the other properties of the plant, including the source of carbon
dioxide and light, the length and type of plant, and the
environment on which it is tested.
The rate of photosynthesis was calculated.