Transcript Function of Leaves

The Function of Leaves
Leaf Types and Patterns
• Five different types of leaf patterns
– Needlelike or scalelike
– Opposite compound leaves
– Opposite simple leaves
– Alternate compound leaves
– Alternate simple leaves
Leaf Types and Patterns
• Trees with needlelike or
scalelike leaves.
• Conifers cone bearing
trees
• Gymnosperms: trees
whose seeds are
exposed (this is opposed
to angiosperms whose
seeds are enclosed in an
ovary that ripens into a
fruit.
Leaves opposite
(compound and simple)
Leaf Types and Patterns
• Leaves Opposite and
compound
• Compound leaves contain
leaflet which lack buds at
their base
• Leaves line up opposite or
across from each other on
the stem.
Leaf Types and Patterns
• Leaves Opposite and
simple
• Buds at the base of
the leaf.
• Twig is woody
• Leaves align across
form each other
Alternate leaves
(compound and simple)
Leaf Types and Patterns
• Alternate simple leaves
• Single leaf which
contains a bud at the
base of the leaf stalk.
• Leaves alternate along
twig.
Leaf Types and Patterns
• Alternate compound
leaves
• Compound leaves
contain leaflet which
lack buds at their
base
• Leaflets alternate
along the woody twig.
Adapted for Photosynthesis
• Leaves are usually thin
– High surface area-to-volume ratio
– Promotes diffusion of carbon dioxide in,
oxygen out
• Leaves are arranged to capture sunlight
– Are held perpendicular to rays of sun
– Arrange so they don’t shade one another
Leaf Structure
UPPER
EPIDERMIS
cuticle
PALISADE
MESOPHYLL
xylem
SPONGY
MESOPHYLL
phloem
LOWER
EPIDERMIS
O2
CO2
one stoma
Mesophyll:
Photosynthetic Tissue
• Mesophyll Cells have
chloroplasts
• Chloroplasts are the
Organelles which capture
energy from the sun to
drive photosynthesis.
• Photosynthesis converts
CO2 into sugars and
starch
sunlight
water uptake
carbon dioxide uptake
ATP
LIGHT
DEPENDENTREACTIONS
ADP + Pi
NADPH
LIGHT
INDEPENDENTREACTIONS
NADP+
P
oxygen release
glucose
new water
in-text, p. 95
leaf’s upper surface
photosynthetic cells
two outer
layers of
membrane
inner membrane
system (thylakoids,
all interconnecting
bychannels)
(see next slide)
Fig. 6.3a, p. 94
stroma
sunlight
excitation
energy
reaction center (a specialized chlorophyll a molecule)
PHOTOSYSTEM
Fig. 6.9, p. 98
The Rainbow catchers
• Pigment Molecules absorb wavelengths of
light
• Most pigments can absorb only certain
incoming wavelengths
• Chlorophylls are the main photosynthetic
pigment
chlorophyll b
Wavelength (nanometers)
Wavelength absorption (%)
Wavelength absorption (%)
chlorophyll a
beta-carotene
phycoerythrin
(a phycobilin)
Wavelength (nanometers)
Fig. 6.6a, p. 97
sunlight
water uptake
carbon dioxide uptake
ATP
LIGHT
DEPENDENTREACTIONS
ADP + Pi
NADPH
LIGHT
INDEPENDENTREACTIONS
NADP+
P
oxygen release
glucose
new water
in-text, p. 95
Carotenoids
• The Carotenoids are
accessory pigments that
absorb light of blue-violet and
blue-green wavelengths and
reflect yellow, orange, and red
ones.
• Carotenoids color many
flowers, vegetables and fruits.
• They are less abundant than
chlorophylls in green leaves
but in many plant species, they
are visible in autumn
Autumn Foliage
• In late summer , leaves begin to forming
layers of cells at the leafstalk base to help
the leaf detach and heal the resulting scar
• As the these cells continue to grow they
begin to clog the leave vains
• The dominant pigment, Chlorophyll is no
longer renewed and disintegrates quickly,
revealing the yellow and orange pigments
of the carotenoids
Autumn Foliage
• Because these red pigments require high
light intensity and elevated sugar content
for their formation, the colors appear after
a period of bright autumn days and cool
night, which prevent accumulated sugar
from leaving the ding leaf