ISOLATING CHLOROPHYLL AND TESTING FOR STARCH IN ALEAF
Materials:A leaffroma green and white coleusplantor from a"wandering
Jew" plant(also calledTradescantia),alcohol, a double boiler, dilute iodine,
a dish, a forceps or a large kitchen spoon.
Follow this procedure:Remove a green and white leaf from theplantyou
have chosen. Using themethodyoujustlearnedinstudyinghow a green leaf
producesfood, boil thechlorophyllout of the leaf. (Again, be carefulnotto
expose thealcoholto direct flame!) Now, place the boiled leaf in a dish and
test it for starchwith dilute iodine. Be sure you wash off the excess iodine
solution.
You will observe:The partofthe leafthatoriginally was green became
blue-black. Thepartof the leafthatoriginally was whiteremainedwithout
pigment.
Only leaves or parts ofleaves thatcontain chlorophyll are active in
photosynthesis. Therefore,the whitepartof the leaf you tested didnotcontain
starch,proofthatit wasnotpartof theplant'sfood-makingfactory.THE UNDERSURFACE OF ALEAF- STOMATES
Materials:Ageraniumleaf, a single-edgedrazorblade orsharpparing
knife, tap water, a medicinedropper.
Follow this procedure:With therazorblade or sharpparingknife, peel
off as thin a piece of the underneathsurface of ageraniumleaf as you can.
Place it in adropofwaterin the middle ofa slide. Carefully cover with a
cover slip. Observe firstunderlow power ofyourmicroscope, and thenunder
high power.
You will observe:Small openingsappearingat intervals. Each openingis
encircled by twokidney-shapedcells.