Transcript why only in autumn leaf changes

Middle School Science
Mrs. Figoten
DO LEAVES ON TREES
IN ALL BIOMES
CHANGE COLOR?
Leaves change color
seasonally only in
deciduous forests.

Warm summers & cold winters

50+ cm precipitation/yr

Trees shed leaves yearly
AUTUMN LEAF CHANGES
What signals leaves to change
color in autumn?

Earth’s tilt changes in Northern
Hemisphere

Less daylight,
cooler temperatures
AUTUMN LEAF CHANGES
What causes leaf color?

3 pigments in each leaf- the
amount in each leaf varies
 Chlorophyll
 Carotene
 Anthocyanin

Leaf appears green

Present in leaf membrane

Needs sunlight in order to make
food for tree through
photosynthesis

Leaf appears yellow

Remains in leaf membrane as
chlorophyll disappears

Helps with photosynthesis

Birch & Hickory leaves
have lots of carotene

Leaf appears red/purple

Present in cell sap

Reacts with sugar from photosynthesis

In some trees, sugar in leaves increases
in autumn

Red Maple, Red Oak & Sumac leaves have
lots of anthocyanin
WHAT DO PLANTS
NEED FOR
PHOTOSYNTHESIS?
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DOES ANYTHING ELSE MAKE
ITS OWN FOOD USING
PHOTOSYNTHESIS?