Tigers Essay, Research Paper
Let There Be Light ?
Introduction
When we look at the sun, what do we see? Other than to squint our eyes and put your
sunglasses on, you can see that the light is very bright and white-yellow in color.
However, looking at light through a prism relates a different story. If Light is put up
against a prism it is refracted or bent into a rainbow which contains the primary colors of
light in which red light bends the least and violet bends the most ( Jude, 1999). The
primary colors of light consist of red, orange, yellow, green, blue, and violet . Light is a
wave that consists of oscillation in electric and magnetic fields that can travel through
space. Plants absorb light in a process called photosynthesis( Gammon, 1999).
Photosynthesis is defined as the process by which green plants and certain other
organisms use the energy of light to convert carbon dioxide and water into the simple
sugar glucose. Photosynthesis provides the basic energy source for virtually all
organisms. An important byproduct of photosynthesis is oxygen, on which most
organisms depend. Plant photosynthesis occurs in leaves and green stems within
specialized cell structures called chloroplasts. One plant leaf is composed of tens of
thousands of cells, and each cell contains 40 to 50 chloroplasts. The chloroplast, an
oval-shaped structure, is divided by membranes into numerous disk-shaped
compartments. These disklike compartments, called thylakoids, are arranged vertically in
the chloroplast like a stack of plates or pancakes. A stack of thylakoids is called a
granum (plural, grana); the grana lie suspended in a fluid known as stroma. Embedded in
the membranes of the thylakoids are hundreds of molecules of chlorophyll, a
light-trapping pigment required for photosynthesis. Additional light-trapping pigments,
enzymes (organic substances that speed up chemical reactions), and other molecules
needed for photosynthesis are also located within the thylakoid membranes. The
pigments and enzymes are arranged in two types of units, Photosystem I and Photosystem
II. Because a chloroplast may have dozens of thylakoids, and each thylakoid may contain
thousands of photosystems, each chloroplast will contain millions of pigment molecules.
( Jude, 1999). This light converting into energy occurs in all plants. Photosynthesis is
responsible for plant growth and development due to light energy from the sun. This
experiment asked the question, Which type of light do plants favor the most? A total of
eighteen plants were subjected to two different types of light, nine were subjected to red
light and nine were subjected to green light. In carrying out the experiment I devised a
null hypothesis and an alternate hypothesis, Ho – There is no difference between growth
rates in plants subjected to green light verses plant growth in plants subjected to red
light. Ha – There is a difference between growth rates in plants subjected to green light
verses plant growth in plants subjected to red light.
METHOD
The procedure in conducting this experiment was very basic. The materials used in
this experiment included; twenty pea seeds with radicle showing, 1 – 2 gallons of water,
two planting trays with 3 X 4 planting containers, so a total of twelve of which only 10
were used, potting soil, a small shovel, red and green bulb lamps. Note: This experiment
was carried out under no other exposure of light other that the ones being tested ( red &
green ). To limit the amount of ?undesired? light and prevent an overlap of light between
the two colors, cardboard boxes were put around and in between the two plant trays.
Attempt to find a room that is dark as possible with the least amount of visible light to
setup this experiment, place potting soil in the 3 X 4 tray containers until half-full. Place
pea seed in potting soil, pushing down slowly until the pea seed was half under the soil
and a green radicle could be seen. Place red and green lamp around the trays making sure
there is no overlap of light. Surround the area with cardboard. Water each individual
container. Note: Take all measurements in Centimeters. Record all measurements in
notebook. Describe the plants and how they are growing, e.g. withered, fallen down,
weak, etc.
Results
My findings showed me that green light plants grow at a faster rate than red light
plants do. This was confirmed by the provided graphs on the preceding pages. The
statistical tests of the significance of the difference between two groups or the t-test is
also shown in the preceding pages. I started recording data after leafs had shown. On first
day of recording data, the green light plants seemed very alive With tiny leafs at the
upper part of plant, the red light plants seemed withered and not much growth observed.
The second day, one could determine that the green light was better for the plants. The
green light plants were very elongated with tiny leafs and some had fallen over. The red
light plants were showing minimal growth but were strong and did not fall over. The last
day the green light plants were all over the tray container. They were all like vines with
little or no leafs. The red leafs were all standing upright and showed some growth, they
had more branches on top and less on bottom. There were inter-nodel difference recorded
where the red light plants were 5 cm apart from node to node and the green light
inter-nodel differences of 6-8 cm apart. These values were all on average.
Discussion:
Interpretation of the given graphs clearly shows that the green light plants grew higher
in length compared to the red light plants. Interpretation of the t-test shows that there was
a significant amount of difference in my groups. The t-test supports my results. The red
and green light plants both grew more vertically than horizontally because they lacked
the required light to grow leafs and branch more horizontally. This points out that plants
do not use only one type of light for energy. An interesting observation that was noted
was that the green light plants were all fallen over but the red light plants were standing
upright. This leads us to speculate that red light plants grow at a slower rate then green
light plants but red light plants are more stronger. The results accepted the alternate
hypothesis (Ha). Research on how light behaves and is absorbed provided some insight
as to what is actually going on in this experiment. A substance absorbs a single type of
light and reflects back the light not absorbed. For example, the green plants in this
experiment can be described as being green in color, meaning that the plants are
absorbing all the other colors of light on the visible spectrum and reflecting back green
which is what your eyes see ( Gammon, 1999 ). This is related to my experiment because
green plants need many different colors of light from visible spectrum, this experiment
only subjected plants to green and red light resulting in more vertical growth due to the
deficiency of required colors of light. Experimental error in this experiment could have
occurred due to ? undesired light ? coming in from uncovered portions of the
experimental area. Error possibly occurred due to times data was recorded, three days
spanned over two weeks including weekends so there was no daily recording of data, that
is why there is good amount of increase on the last day. The time frame of this
experiment was three days. An experiment done with a longer time frame could have
shed better light on the subject. No pun intended.
Gammon, Steven D. 1999 General Chemistry, Houghton Mifflin Co. Boston, MA
Jude, Alex 1993-1999 Encarta 99, Microsoft Corp. , CD