Plant Lab. What effect does the amount of light have on the growth of a bean plant measured by the height of the bean plant?

Design your own lab

By Kaushik Surisetty per.5

Problem: What effect does the amount of light have on the growth of a bean plant measured by the height of the bean plant?

Background and Hypothesis: Photosynthesis forms the basis for this experiment. This is the process by which a plant makes food for itself in the form of glucose from the raw materials around it. The energy needed for photosynthesis comes from sunlight, which is the variable for this experiment. The substance that absorbs sunlight is chlorophyll, which is mainly contained in chloroplasts. The energy from the sun is used to split water molecules which is the process photolysis, this through the use off photo systems pump protons in to the lumen of the chloroplast creating a concentration gradient. When protons moved through CFOCF1 complexes to the stroma which has a lower concentration of hydrogen, this creates ATP. This energy is used to convert carbon dioxide (CO2) and water into sugars. This conversion creates the waste product oxygen and the sugar glucose that the plants uses to nether store in food reserves or uses to grow through cellular respiration. The cells of the plant use the glucose to grow roots, cells and stem which results in an increase of height. Without being able to photosynthesize, plants will stop growing and die since there is no form of useable energy for its cells. In a plant growing in the dark the chlorophyll will slowly be destroyed causing them to use their food reserves. Once the reserves have been used the plant will die. This is what happens in plants that are not grown in sunlight. Etiolating is a phenomenon that occurs in plants not being grown in sunlight, where the stem of the plant rapidly elongates to increase the probability of the plant finding light. In order to carry out this etiolation the plant must use its food reserves, so if the plant does not find light having used these reserves, it will die seen there is no useable energy for the cells of the plant to grow. The plant that are in the sun will continue to grow as there is a limitless amount of sunlight and grow much taller that the one in the dark which may not receive its needed amount of sunlight to process glucose and grow through photosynthesis. The more sunlight the bean plant receives it should grow much more than the bean plant that has been in the dark if it hasn’t already died. This is because the bean plant needs light to produce glucose through photosynthesis and this glucose will sustain the current and future cells and continue to grow. Where as the bean plant that is in the dark, it won’t have enough sunlight to properly photosynthesize and therefore growing until its current reserves are empty and may eventually die (Duncan Garnett, 2007). According to Duncan Garnett from the background information, if an increase in amount of light occurs, then there should be an increase in height of bean plant’s growth will happen, because there is more light that the plant are receiving for photosynthesis which is the process of making more glucose that can be used not only to maintain the current cells of the plant but provide energy for the plant’s newborn cells and producing new cells resulting in the increase in height that we should observe. But there is a limit to the amount of light, this is because there are limitations on the number of photo systems which absorb the light energy and convert in to stored chemical energy. The plant has only a restricted number of photo systems that can work at one time. If the light is too intense, it may influence temperature which may increase growth and may also increase the amount of transpiration.

Prediction: The excessive amount of light will produce a plant that is 10% taller than the plant grow in the normal sunlight and be more than 30 % taller than the one in the dark .

Experimental Design: This experiment will take place over almost 3 weeks to find out the effect light has on the growth of bean plants. It will be in an environment with controlled light, with equal amounts of plants being grown in the light and in the dark. All elements of the experiment other than the amount of light will be kept the same, ...

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Prediction: The excessive amount of light will produce a plant that is 10% taller than the plant grow in the normal sunlight and be more than 30 % taller than the one in the dark .

Variables:

The manipulated variable is the amount of light the plant will receive; this will be varied by the location of the plant in different light intensity areas.
The responding variable is the change in the amount of plant growth which will be measured by the height in centimeters.
The controlled variables include the amount and composition of the soil and water, the size of the container in which the seed will grow, the environment in which the plant grow and the species of plant.
The control group will receive suitable sunlight conditions which will ensure the accuracy of our results be kept near a south facing window for suitable planting conditions.
The experimental group will receive varying amounts of light by being placed in locations of no light, moderate light and heavy light conditions.

Materials:

8 bean seeds
8 small pots
1 bag of soil
Large amount of Water
Ruler
Gloves
Pencil, paper, table… for recording data
Paper towel
3 Cardboard boxes and cutters.
3 trays

Apparatus Description:

Since this experiment will be varying the amount of light each plant receives, there will be different equipment used for each plant.

Get three identical boxes at least 50 cm tall. Cut the upper flaps of the box and place it vertically.
Create a box that is covered internally by aluminum foil so that rays of light from the sun bounce to the plant and the other unabsorbed rays of light would be hitting the foil and bounces back upon the plant. This increases the amount of light the plant receives and its chances to produce more glucose.
Create a closed box is meant to limit the light entering the box. Do this by placing a large black screen in front of the box. To make this screen put a black cloth over the opening. This will limit the light but still let some through so life.
Leave the last box alone as it will be our control.
For each box poke holes for gas exchange.
Make sure to place a collection tray to gather excess water from under the plant.
Place these boxes and the plants in the same location which control humidity, temperature and amount of gases available.
Make sure pots have holes through the bottom for excess water.

Here is a diagram for the set up of this lab:

Procedure:

Germinate seeds by soaking beans in water overnight, and then placing them in a wet paper towel for half a day.
Fill pot with soil and place seed on top of soil and place a light 0.2 cm layer over top. Don’t not push Bean into the soil.
Let all pots grow and sprout. Some will not sprout. Only 3 plants are needed
Place 1 pots near a south facing window, this will be the control for suitable planting seeds. If only few are
Place 1 pots inside of a cardboard box that will be closed. This will be the no light plant.
Place 1 pot in the aluminum foil cardboard box and face the opening of the box toward a sunny window.
Water each plant 25 ml every morning before or near sun rise.
Record measurements for each day in the table. Repeat these steps daily until desired amount of data is received.

This experiment should be repeated multiple times for accuracy.
The box that is covered by the aluminum foil is used so that rays of light from the sun bounce to the plant after hitting the foil and this increases the amount of light the plant receives. The closed box is meant to limit the light entering the box. When preparing these boxes make holes for ventilation and so that the exchange for gases can occur.
Place the plant in the same location which control humidity, temperature and amount of gases available.
Make to place a collection tray to gather excess water from under the plant.

Evidence: The Effects of Varying Amounts of Light on the Growth Height of a Plant.

Qualitative Data:

Only some seed sprouted during the germination process. Only three of the eight had sprouted on day 7. Once the seed had surfaced, the seed part of the plant had risen and grown upward until about 15 and then the outer brown casing called the seed coat left off and the seed began to open, and there were visible leaves that were spreading from the seed and the leaves grew taller and developed. After the day of germination only 5 seeds developed visible root tips and of which 2 were largely longer that the others. After 5 days, the first stem was seen called the hypocotyls. Near day 7, the hypocotyls slowly were rising and were discovered to be pushing cotyledons with a seed coat that fell off as the cotyledon stated to turn opposite of the soil and it grew upwards. Near the 15 cm mark, there were leaves that were growing squeezed between the two cotyledons which now opened and the stem between the leaves and cotyledon began to elongate and grow taller.

Analysis:

Evaluation and Synthesis: With this experiment the hypothesis has been proved. As we can the end result is that the plant growing in the high light was the tallest proving that light does effect the plant’s ability to grow. This is due to the fact that plants use the sunlight to make sugar through the process of photosynthesis. To produce food, a plant requires energy from the sun, carbon dioxide from the air, and water from the soil. During photosynthesis, it splits carbon dioxide into carbon and oxygen, adds water, and forms carbohydrates (starches and sugars). Oxygen is a by product. The formula for photosynthesis can be written as follows: Carbon dioxide + Water + Sunlight = Sugar + Oxygen or 6 CO2 + 6 H20 + Energy => C6H1206 + 6 02 .After producing carbohydrates, a plant either uses them as energy, stores them, or builds them into complex energy compounds such as oils and proteins. All of these food products are called . The plant uses them when light is limited, or transports them to its roots or developing fruits. Photosynthesis occurs only in the layers of plant leaves and, in some instances, in mesophyll cells in the stem. Mesophyll cells are sandwiched between the leaf's upper and lower epidermis and contain numerous , where photosynthesis takes place. , the pigment that makes leaves green, is found in the chloroplasts. It is responsible for trapping light energy from the sun. Often chloroplasts are arranged perpendicular to incoming sun rays so they can absorb maximum sunlight. So the more light there is being absorbed by the plant the more glucose produce to be used by the cells to growth and divide quicker. “If any of the ingredients for photosynthesis: light, water, and carbon dioxide, is lacking, photosynthesis stops. If any factor is absent for a long period of time, a plant will die.”(Ann Marie VanDerZanden, 2008).

Lab evaluation: Sources of error may have included some of the plants weren’t getting the same amount of water as some of the pots leaked more water than others. The sprouting time may have been different depending on seed and its size. The temperature may have been influenced by the high light conditions which would have made a huge difference. Any of these areas could have disrupted the results and mostly likely if there was a contained system that was closely monitored, then there would had been a valid result. The black screen may have influenced the temperature with in the box. The seeds sprouted during different times in the day but for did to be controlled w would have to grow many seeds and take out a average group with this. The results do show that the excessive light did have an impact on plant growth by to be sure it wasn’t’ the actually behavior or status of the seed it self can’t really be controlled. The prediction was partially falsified as the high light growing plant grew close to 10% shown by the 4cm increase but there was a 66% increase when compared to the plant grown in the dark. This is partially because of the underestimation of how low amounts of light effect plants and partially because of the underestimation of the apparatus used.

Reference:

Botany Basics. In http://extension.oregonstate.edu/mg/botany/index.html. Retrieved September 7, 2008 from http://extension.oregonstate.edu/mg/botany/photo.html
Biology Coursework by Duncan Garnett Experiment 1-"Comparing the Growth of Plants Grown in the Light and in the Dark." 123HelpMe.com. 07 Sep 2008
<http://www.123HelpMe.com/view.asp?id=147949>.
What is Photosynthesis? Retrieved September 7, 2008 http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookPS.html

Plant Lab. What effect does the amount of light have on the growth of a bean plant measured by the height of the bean plant?

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