Protocol set 9 photosynthesis
Abstract:
The purpose of this lab is to investigate the relation between the rate of photosynthesis and the
type of wavelengths, know which color or wavelengths of light is best preferred by the plants to
let the process of photosynthesis to occur , which is how plants can basically create their own
food.
Introduction: photosynthesis converts light energy to the chemical energy of sugar another
organic compounds. This process consists of series of chemical reactions that require carbon
dioxide and water .. light energy drives the reaction ,oxygen is the byproduct of the
photosynthesis and it is released into the atmospheres
On our experiment we are going to investigate the response of leaf disks after being exposed to
different wavelength and measure the number of floating disks during 15 min, we choose to use
yellow and green light color.
We are predicting that no disks will be able to float when the light is green , because the
chlorophyll inside of the leaves reflects the green light, so it will not be absorbed and therefore
no oxygen production. Same result with our control samples that were hidden on dark area, there
were not be floating disks because of the absence of light.
results:
number of floating disks(yellow light) and
number of floating disk(green light)vs
time(seconds)
10
number of floting disks
9
8
7
6
number of floating
discs(yellow light)
5
4
number of floating disc(green
light)
3
2
1
900
840
780
720
660
600
540
480
420
360
300
240
180
120
60
0
0
time (seconds)
Discussion: as we can see on the graph. Disks being exposed under the yellow light, began to
floate a few seconds after the experiment started.The number of floating disks is related to the
wavelength color. As we learned through the handout, plants absorb and reflect slightly different
wavelengths of light.
We know that what make the disks to float is the presence of air, when the leaf disk is given all
the conditions necessary, they use the Co2 to undergoes photosynthesis, they will then be
accumulation of O2 that cause them to float. And this is what happened with the yellow light.
The byproduct of photosynthesis is the net production of O2 gas. And the rate of O2 production
by the light reactions varies with the light color because light is energy source for O 2 formation.
There was no floating disk with the green light, which means no photosynthesis(=no O2
production), because the chlorophyll inside of the leaves reflects green light, so it will not be
absorbed as much as the other colors. Our hypothesis approved to be right.
Controlled sample : When we put our leaf disks in the dark, they will eventually remained sinked.
Without light energy, no photosynthesis will occur, so no more O2 gas will be produced.
However, our leaves will be undergoing aerobic cellular respiration using the product of
photosynthesis(C6H12O6 + O2). this process will continues in the dark, so the disks will use the
accumulated O2 gas. They will also produce CO2 gas during respiration, but CO2 dissolves into
the surrounding water much more easily than O2 gas does and isn’t trapped in the interstitial
spaces, so disks remained sinked.
Conclusion: from this lab we can conclude:
Over all, plants survive with two process : light-dependent reactions: photosynthesis, and lightindependent reaction: cellular respiration.
Even plants have their favorite colors, some wavelengths( color) of light are more effective than
the other at driving photosynthesis.
Photosynthesis requires light, but plants don't use all the colors that make up the white light (Sun
light).