Boiled Leaf Lab

Preparation:  Cut 2 one inch square pieces of thick cardboard (like cereal box)  Clip the two pieces of cardboard to a leaf still growing and attached to a plant  Label your squares  Write down a prediction about what you will find under the cardboard squares  Sketch the leaf with the cardboard on it

 Put Label on paper  Prediction

Sketching  Labels  Size/Scale  Details – shading  View  Top  Bottom  side

A day or two later  Prediction:  Sketch the leaf (1)-Label “Before”  Take off the cardboard  Sketch the leaf noting any color changes (2) – Label “After”

Saga continues…  Boil the leaf in water for 5 minutes  Sketch the leaf noting any color changes (3) – Label “Boiling Water”  Note the change of color in the water  Boil in alcohol for 5 minutes MUST WEAR GOGGLES! AVOID INHALATION!  Sketch leaf noting any color changes (4) – Label “Boiling Alcohol”

Lastly…  Place iodine on the leaf  Sketch the leaf noting changes in color (5) Iodine How does the leaf compare to the original leaf and cardboard and why?

Results – Picture 2  What did it look like when you took the shape off?  Should still be green  Is it still alive?  Yes – chlorophyll still present

After boiling in Water (3)  Color change?  Green to drab green  Purpose: Break down cell walls – cellulose – paper – gets soft if you boil it  Water – yellowish-green

After boiling in alcohol (4)  Color? Texture?  Yellow and a bit crispy  Liquid?  Green – removed the chlorophyll  Is chlorophyll soluble in water?  No – if it were water and rain would wash the chlorophyll away

After Iodine (5)  Iodine reacts with starch to turn black/dark blue  Where was the starch? How come?  Shape – burns glucose – then starch (polymer made of glucose) – imports glucose  Roots and Bark

Class of 09 leaf

Why do leaves change color in the fall?

What triggers the leaf to stop photosynthesis?  Amount of sun light  Shuts down photosynthesis  Chlorophyll breaks down  See what is left

Why do leaves drop off?  sunlight decreases -the veins that carry sap into and out of a leaf gradually close.  A layer of cells, separation layer, forms at the base of the leaf stem.  When this layer is complete, the leaf is separated from the tissue that connected it to the branch, and it falls.  Oak leaves are the exception. The separation layer never fully detaches the dead oak leaves, and they remain on the tree through winter.