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