Transcript Valentina, Alexandru, and Elizabeth present…

Valentina, Alexandru, and
Elizabeth present…
Every
autumn some
leaves change
COLOR
Green leaves turn to various shades of
yellow, orange, red...
But WHY does this
happen???
Well, chemistry can
explain it!!!
•First, we should know why the leaves
are green
•The green pigment in leaves is
chlorophyll
•Absorbs red and blue light from the
sunlight
•The light reflected by the leaves is
diminished in red and blue and appears
green
•Chlorophyll
molecule is
large
•It is not
water
soluble
(C55H70MgN4O6)
•Chlorophyll molecules are attached to
chloroplasts inside the cells.
•Chloroplasts are the site of photosynthesis
light
x CO2 + y H2O
chlorophyll
x O2 + Cx(H2O)y
•The energy of the light absorbed by
chlorophyll is converted into chemical
energy stored in carbohydrates.
•It causes plants to grow, flower,
and produce seed
•The synthesis of chlorophyll
requires sunlight and warm
temperatures.
Another
pigment
found in the
leaves
is carotene
•Carotene
absorbs bluegreen and blue
light
•The light
reflected from
carotene makes
the leaves
appear yellow
The formula for
carotene is C40H36
This large molecule is located in the chloroplasts of many plants
•When carotene and chlorophyll are present in the same
leaf, the light
reflected appears green
•Carotene is a more stable
compound than chlorophyll
•It is the remaining carotene
which
causes the leaf to appear
yellow
The third class of pigments
are the
anthocyanins
•Anthocyanins are
responsible for the beautiful
red color of the maple
leaves
•Anthocyanins are also found in ripe apples and grapes
•The red color is determined also by the acidity of the
cell sap
•The more acidic the sap is, the
brighter the red of the leaf is
•Anthocyanins are formed by a
reaction between sugar and certain
proteins
•In the autumn the concentration of
sugars in the leaves increases so…
•More anthocyanins that will turn
the leaf red are produced
There are six different
kinds of anthocyanins!
The shortening days and cool nights of autumn trigger
changes in the tree…
•A corky membrane between the branch and the leaf
stem grows.
•The production of the chlorophyll in the leaf declines, so
the other pigments take over
•Weather also influences
the intensity of autumn
colors.
•Dry, cold sunny
weather destroys
chlorophyll and
enhances anthocyanin
production
•The brightest colors
are produced when
dry sunny days are
followed by cool, dry
nights
Now you know why the
colors
of the leaves change!!!