Simon Nguyen
2/22/09
Per. 2
The Effect of Light Intensity on Spinach Leaf Disks
We monitored the effect of light intensity (lamp) and measured the rate of photosynthesis in spinach leaf disks. The question we want to answer is: how does light intensity affect the rate of photosynthesis in leaf disks? Our independent variable is: the distance from the light (intensity). Our dependent variable is: the amount of time it took for the disks to float. Our control is the syringe covered in aluminum foil. Our constants were the same syringes, straws, spinach plants, and the same solution.
At first we prepared 3 syringes, two for experimental use and one for the control. We took a straw and punched out 10leaf disks from spinach leaves. Second we blew ten leaf disks into each body of the syringes. Third we filled the syringes with a bicarbonate solution to the 8ml mark and held the syringe upward and pushed out the excess air by pressing the plunger. Fifth we sealed the tip of the syringes and vacuumed the bubbles off the edges of the leaf disks. Six we checked to see if the syringes were filled to the same level and added removing the solution and wrapped one syringe in foil and left the other two wrapped. We then prepared the two experimental syringes, one close to the light and one away, with the tips up in front of the light and one 25cm away and one 50cm away from the lamp.
My hypothesis was: if we add light to the plant disks the disk will float because plants absorb light to produce oxygen. I support my hypothesis because I know that plants absorb light energy because they have a light absorbing pigment that is found in the cells of green plants called chlorophyll. So if there is a source of light energy a plant will use photosynthesis to create oxygen causing the disks to float.
In our observations we saw that the syringe closest to...