WHY LEAVES TURN COLOR IN THE FALL
Materials:All you need are several leaves from the same tree, but collected
at different timesofthe year. A botanyhandbookor a biologytext-book
will be helpful for identifying leaves you are not sureabout.Then, too, you
will need thematerialsyou used previously in making collections ofpressed
ferns and leaves.
Follow this procedure:Insummercollect the green leavesofmaple, ash,
elm, oak, sycamore, poplarand othertrees. Carefully dry and press these
leaves between newspaperunderheavy books. Collect fallen leavesofthe same
trees in the early fall. Comparethe colors of these leaves with those ofthe
pressed green leaves. Make athirdcollectionoffallen leaves in the late fall,
andcomparethem to the others.
You will observe:The early fall leavesofelm, ash, sycamore and some
maple trees will be yellow orbrilliantorange. Sugar and red maple leaves will
be deep, vivid red. Some oak leaves will be purple, others scarlet.
The late fall leaves of all these trees will be dull, dry, brown and will fall
apartor crumble easily.
Aftera summer ofmanufacturingfood, thechlorophyllbodies (chloro-
plasts) of green leaves die because they havecompletedtheirjob. Excess food
made duringthe summer is stored in thetrunkand roots ofthe tree for use
duringwinter.
There are pigmentsotherthangreen in most leaves, but they are hidden
under the chlorophyll. However, when the green color dies, these other
pigments show up. This is whataccountsfor the vivid shades ofautumnleaves.
Then, in late fall when the weather becomes cold, theotherpigments and
the cellsofthe leaves die. Dry, crumbly brown leaves are actually "dead."
The fallingofthese leaves from the tree in late fallpreparesthe tree for winter
cold and for snow. Otherwise, wintertemperatureswould freeze the water in
the veins of the leaves, and this would eventuallyharmthe tree itself.
Trees whose leaves die and fall offannuallyare known asdeciduoustrees.
But the leavesofothertrees, calledevergreens,do not lose their leavesduring
fall. The leaves of evergreens are more like needles, with a thick,protective,
waterproof,waxy covering,thanlike what we usually thinkofas leaves. Some
familiar evergreens are pines, firs, hemlocks, spruce andtamaracktrees.